Welch Allyn SureTemp 670 Specifications

Thermo Menu
Operation Manual
SureTemp® & SureTemp 4®
Model 670 & Model 675 Thermometer
Technical Manual
© 1996 by Welch Allyn, Inc. All rights reserved. No part of this manual may be reproduced or transmitted in any form or by
any means, electronic or mechanical, including photocopy, without prior consent in writing from Welch Allyn. Printed in the
U.S.A.
Welch Allyn and SureTemp are trademarks of Welch Allyn, Inc. All rights reserved.
Technical Manual
TABLE OF CONTENTS
WARRANTY .........................................................................................................................................1
SPECIFICATIONS ................................................................................................................................2
OPERATIONAL CHARACTERISTICS ..................................................................................................2
INTRODUCTION ...............................................................................................................................2
BASIC SYSTEM DESCRIPTION .......................................................................................................3
Operating Controls and Components.................................................................................................4
Setup .................................................................................................................................................4
Instrument Reset/Self Tests ...........................................................................................................4
Probe Initialization/Self Tests .........................................................................................................5
Normal Mode .....................................................................................................................................6
Monitor Mode.....................................................................................................................................7
Pulse Timer .......................................................................................................................................7
Backlight/Temperature Recall............................................................................................................7
F/C Switch .........................................................................................................................................8
Biotech Mode.....................................................................................................................................8
Battery Life ........................................................................................................................................9
PREVENTATIVE MAINTENANCE ...................................................................................................... 10
Cleaning and Sterilization ................................................................................................................ 10
Routine Cleaning .......................................................................................................................... 10
ETO Gas Sterilization Procedure.................................................................................................. 10
Battery Removal and Replacement ................................................................................................. 11
CALIBRATION TESTING ................................................................................................................... 12
Calibration Key Procedure ............................................................................................................... 12
Model 9600 Procedure .................................................................................................................... 12
THEORY OF OPERATION ................................................................................................................. 13
Technical Overview ......................................................................................................................... 13
Probe Enhancements ...................................................................................................................... 14
Probe Switch ................................................................................................................................... 14
Monitor Mode................................................................................................................................... 14
Normal Mode, Model 670................................................................................................................. 15
Normal Mode, Model 675................................................................................................................. 15
Power Supply .................................................................................................................................. 15
Microprocessor Usage..................................................................................................................... 15
Reset/Self Tests .............................................................................................................................. 16
Microprocessor Clock ...................................................................................................................... 16
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Temperature Measurement and Display .......................................................................................... 16
Battery Voltage Reading.................................................................................................................. 17
A/D Power Control ........................................................................................................................... 17
Probe Detection............................................................................................................................... 17
Probe Warming (675 Oral probes only) ........................................................................................... 18
EEPROM ......................................................................................................................................... 19
Liquid Crystal Display ...................................................................................................................... 19
Backlight/Temperature Recall.......................................................................................................... 20
Horn................................................................................................................................................. 20
F/C Switching .................................................................................................................................. 20
Timer ............................................................................................................................................... 20
ERROR CODES ................................................................................................................................. 21
Error Code Table ............................................................................................................................. 21
TROUBLESHOOTING........................................................................................................................ 22
Equipment Required ........................................................................................................................ 22
Terminology..................................................................................................................................... 23
Troubleshooting Table ..................................................................................................................... 24
FIELD SERVICEABLE REPAIRS ....................................................................................................... 30
FACTORY SERVICEABLE ONLY REPAIRS ...................................................................................... 30
FIELD SERVICEABLE PARTS ........................................................................................................... 30
THERMOMETER DISASSEMBLY ...................................................................................................... 31
THERMOMETER REASSEMBLY ....................................................................................................... 38
SUGGESTED SPARE PARTS LIST ................................................................................................... 39
OPTIONS AND ACCESSORIES......................................................................................................... 39
TABLE OF FIGURES
FIGURE 1 - THERMOMETER DIAGRAM .............................................................................................4
FIGURE 2 - THERMOMETER DISPLAY ..............................................................................................5
FIGURE 3 - SYSTEM BLOCK DIAGRAM ........................................................................................... 14
FIGURE 4 - THERMOMETER ASSEMBLY DRAWING ...................................................................... 32
FIGURE 5 - SYSTEM SCHEMATIC.................................................................................................... 34
FIGURE 6 - MAIN PCA ....................................................................................................................... 36
FIGURE 7 - ELECTRONICS ASSEMBLY........................................................................................... 37
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WARRANTY
1-YEAR LIMITED WARRANTY ON NEW INSTRUMENTS: Instrumentation purchased new from Welch
Allyn, Inc. (Welch Allyn) is warranted to be free from original defects in material and workmanship under
normal use and service for a period of one year from the date of first shipment from Welch Allyn. This
warranty shall be fulfilled by Welch Allyn or its authorized representative repairing or replacing at Welch
Allyn's discretion, any such defect, free of charge for parts and labor.
Welch Allyn should be notified via telephone of any defective product and the item should be immediately
returned, securely packaged and postage prepaid to Welch Allyn. Loss or damage in shipment shall be at
purchaser's risk.
Welch Allyn will not be responsible for loss associated with the use of any Welch Allyn product that (1) has
had the serial number defaced, (2) has been repaired by anyone other than an authorized Welch Allyn
Service Representative, (3) has been altered, or (4) has been used in a manner other than in accordance
with instructions.
THIS WARRANTY IS EXCLUSIVE AND IN LIEU OF ANY IMPLIED WARRANTY OR MERCHANTABILITY,
FITNESS FOR PARTICULAR PURPOSE, OR OTHER WARRANTY OF QUALITY, WHETHER
EXPRESSED OR IMPLIED. WELCH ALLYN WILL NOT BE LIABLE FOR ANY INCIDENTAL OR
CONSEQUENTIAL DAMAGES.
The information in this manual has been carefully reviewed and is believed to be accurate; however, no
responsibility is assumed for inaccuracies. Furthermore, this information does not convey to the purchaser
of Welch Allyn or Diatek devices any license under the patent rights to the manufacturer.
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SPECIFICATIONS
•
Case Dimensions
(nominal):
6.25 inches long x 3.7 inches wide x 2.4 inches deep.
•
Case Material:
ABS Plastic.
•
Weight (nominal):
10.5 ounces with batteries.
•
Input:
Welch Allyn Thermistor Probe.
•
Display range:
28.9o C to 42.2o C (84.0o F to 108.0o F).
•
Laboratory Accuracy:
± 0.2o F in the Monitor mode and in a water bath per Welch Allyn
document number 90565-000.
•
Clinical Accuracy:
Meets the proposed ASTM clinical test criteria.
•
Push buttons:
Backlight/Recall and Pulse Timer.
•
Selection Switches:
Normal/Monitor and F/C (No F/C Switch for Euro/German version).
•
Probes:
Interchangeable Oral (also used for Axillary) and Rectal.
•
Power Source:
Three “AA” Batteries.
•
Battery Operating Life: Up to 6,000 temperature measurements (At 72o F ambient temperature
and 15% backlight use).
•
Display Type:
Liquid Crystal Display, 3½ digits plus special icons.
•
Operating
temperature:
16o C to 40o C (60.8 o F-104o F) @ 15% to 95% RH non-condensing
per ASTM E1112-86.
•
Storage Temperature:
-20o C to 50o C (-4o F-120o F) @ 15% to 95% RH non-condensing per
ASTM E1112-86.
OPERATIONAL CHARACTERISTICS
INTRODUCTION
Note: This manual describes both the Model 670 and the Model 675 thermometers. The bulk of the
discussion is equally applicable to both products. Where there are differences, it will be noted as to which
instrument the discussion applies.
The Welch Allyn Model 670 and 675 Thermometers are the next generation of thermistor based medical
grade thermometers providing the accuracy and ease of use of thermistor technology as in the well known
Model 600, with enhancements in speed and features. Model 670 provides a Normal mode oral temperature
in about 10 seconds. Model 675 provides this temperature in about 4 seconds. These are significantly faster
than the typical 30 to 40 second average time to temperature in earlier products. Several other features
have been added, including a temperature recall feature, probe type display, displayed error codes for more
information when operation is abnormal, and a biotech mode to allow further investigation of some internal
parameters without the need for disassembly.
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The basic end user operation of the Model 670 and Model 675 is covered in the User’s Manual and this
manual assumes an understanding of these operations. The following sections will help you determine if the
Model 670/675 is functioning properly and, if it is not, refer you to the proper section to isolate the problem.
There are many things that can be done to check operation before the unit is disassembled. This section
will cover these normal operating characteristics.
BASIC SYSTEM DESCRIPTION
The thermometer system consists of five main components. The batteries, the thermometer instrument, the
wall mount, the probe and the probe cover.
The Model 670 and Model 675 thermometers use three standard alkaline “AA” cells. These batteries are
readily available and provide long life for reduced down time. No battery charging is required.
Note: The use of Ni-Cad rechargeable batteries is allowed. The nominal cell voltage of 1.2 volts for Ni-Cad
(vs. 1.5 volts for alkaline) combined with the lower actual capacity than alkaline will result in a much shorter
time between charging cycles than alkaline battery life.
The main instrument looks and operates very similarly to the Model 600 with enhancements described
below. Basic operation has been kept very similar to that of the Model 600 to ease learning and use.
The wall mount is easily mounted to a wall (or rolling stand) and provides a locking mechanism with a
removable key for securing the instrument. Through the use of available long probe cords, the thermometer
can be used without removing it from the wall mount.
The probe is similar in appearance to the Model 600 probe, but is incompatible with Model 600. Model 600
probes are also incompatible with Model 670/Model 675 instruments. Enhancements to the probe are
detailed in the Theory of Operation section.
Model 670 probes are incompatible with Model 675 probes, but Model 675 probes can be used in Model 670
thermometers.
The Model 675 instrument has a key in the connector receptacle to disallow any but Model 675 probes.
The probe covers are unchanged from previous models and are compatible across all of Welch Allyn and
Diatek thermistor based thermometers. Welch Allyn’s thermistor based probes can be identified by color
combinations as follows:
Handle Color
Top Color Cord Color
Connector Color
Model #
Green
Red
Green
Red
Blue
Red
White
White
Green
Red
Green
Red
Blue
Red
Blue
Red
Green
Green
Modular Phone style
Modular Phone style
Blue
Red
White
White
M600
M600
M650
M650
M670
M670
M675
M675
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Green or Black
Green or Black
Green
Green
White
White
White
White
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Probe
Type
Oral
Rectal
Oral
Rectal
Oral
Rectal
Oral
Rectal
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2
3
4
5
8
6
7
9
10
13
14
11
•F
•C
NORMAL
MONITOR
12
1.
2.
3.
4.
5.
6.
7.
Probe cover box
Probe
Display
Backlight/Recall switch
Timer switch
Display legends
Battery access door
8.
9.
10.
11.
12.
13.
14.
Probe handle collar
Probe cover ejection button
Probe cover storage well
Fahrenheit/Celsius select switch
Normal/Monitor mode select switch
Probe storage channel
Probe connector receptacle
FIGURE 1 - THERMOMETER DIAGRAM
Operating Controls and Components
Setup
If a problem is reported with an instrument, it is sometimes wise to investigate operation before the unit is
reset, but generally resetting the electronics is the recommended starting point in the process.
Instrument Reset/Self Tests
The batteries must be removed from the instrument to reset the internal microprocessor electronics. Follow
the battery removal instructions in the Maintenance section on page 11.
Because the instrument uses very little power, the reset will not occur immediately upon battery removal until
the capacitance of the circuit is discharged. To speed this discharge, after the batteries are out, press the
backlight or timer button for about 10 seconds. The electronics will now properly reset upon battery
installation.
Remove the probe from the probe storage channel and unplug the probe connector from the instrument by
pulling on the connector body. Do not pull on the cord.
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While watching the display, install the batteries per the instructions in the Maintenance section and observe
the power up self test.
The self test includes several internal microprocessor self tests, instrument electronics tests and the display
test. If there are internal electronics problems detected by the self tests, an error code (EX.X) will be
displayed. Refer to the Error Codes section on page 21 for an explanation.
The display test begins with each display segment individually lit in brief and rapid succession. At the same
time, the timer segments are incrementally turned on until all 30 are illuminated. Immediately after this, all
display segments are simultaneously illuminated briefly followed by a display of the software revision in this
instrument. The beeper also briefly sounds at the beginning of the tests, at the 15 second mark of the timer
and at the 30 second mark. If all is well from the power up self test, the display goes blank at this time (with
no probe installed.)
Note: If a probe is installed during this power up time, different results will occur depending on whether the
probe is functioning properly or not. See the Probe Initialization/Self Tests section below for these tests.
At this point, there should be no probe connected to the instrument.
FIGURE 2 - THERMOMETER DISPLAY
If there is no display, any missing segments, or no beeper, refer to the Troubleshooting section on
page 22.
Probe Initialization/Self Tests
With a properly functioning instrument, the probe can be put through self test. The instrument will, if
functioning properly and a probe installed, initiate the probe self test during the instrument reset self test.
Proper instrument functionality should be verified first as described in the Instrument Reset/Self Tests
section before a probe is installed.
With an instrument that passed the Instrument Reset/Self Tests section, install the probe connector first
(with the Diatek or Welch Allyn logo showing) and then fully insert the probe shaft into the storage channel.
Observe the display of the probe type. For Model 670, this probe type display will be very brief (less than 1
second.) For Model 675 Oral probes, the probe type will be displayed for about 10 to 15 seconds or possibly
even longer. Do not withdraw the probe. For Rectal probes, the display is brief. If the display does not
show “OrL” with an Oral probe plugged in, or “rEC” with a Rectal probe plugged in, there is a problem with
the probe, or the probe connector in the instrument. (For Model 670, if no display of probe type is shown, the
probe might be the wrong type for this thermometer and the instrument will not function.)
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If the display goes blank after the probe type display, the probe has passed its tests and the instrument is
ready for use. Do not withdraw the probe during this self test. If the display shows an error code (such as
E5.4), the probe is suspect.
Note: Probes are very sensitive to temperature variations and the self tests include thermal tests that can
be disturbed by any temperature changes. Therefore it is extremely important to minimize thermal
disturbance before and during these tests. Handle the probe only by the probe handle, not the metal shaft,
and minimize the amount of time the instrument is held in the hand before and during these tests.
The instrument stores individual probe characteristics as a result of this test so it is important to reinitialize
the probe after any repair has been done to the instrument or probe.
When removing a probe, always extract the probe from the storage channel first and then disconnect the
connector by pulling on the connector body. Do not pull by the cord.
If there are any problems with probe initialization refer to the Troubleshooting section on page 22.
Normal Mode
After instrument and probe self tests, the system is ready for use. Normal mode operation is the rapid mode
of temperature taking. This mode is selected by the switch on the top of the instrument before the probe is
withdrawn from the probe channel.
Upon withdrawal of the probe from its storage channel, the beeper will sound and every segment on the
display will be illuminated. Load a probe cover at this time and watch for the display to change from the all
segments test to the probe type display; “OrL” or “rEC” followed by °C or °F, which ever is selected. This
display might take several seconds to appear. At this point the instrument is ready for the probe to be
inserted into the patient.
Note: It is possible that the display will switch from the probe type display to the “walking segments” display
and back again several times before the probe is inserted in the mouth. This is acceptable operation and will
not adversely effect the temperature taken, but is indicative of the need to “re-characterize” the probe. Refer
to the Probe Self Tests section on page 5.
Note: The unit cannot be switched from Monitor mode to Normal mode with the probe out of the storage
channel. A double beep will indicate this error and the probe must be returned to the channel to restart the
thermometer.
The thermometer will automatically switch to Monitor mode under some conditions. These are:
1. If the prediction algorithm has not been activated for more than 30 seconds after taking the probe out of
the storage channel.
2. If the instrument determines that room temperature is above 33.9°C (93.0°F).
3. If the thermometer is unable to predict a temperature after 15 seconds due to improper technique such
as excessive probe movement at any patient site (i.e. mouth, rectum).
Note: The thermometer reads the probe temperature immediately upon removal from the storage channel.
If the probe was just replaced from a previous temperature and immediately extracted, insufficient time has
passed to allow the probe to cool to room temperature. This will result in the instrument determining room
temperature to be higher than actual. This could result in the instrument switching to Monitor mode
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immediately if it detects room temperature to be above 33.9°C (93.0°F). For best results, the user should
wait at least 30 seconds between Normal mode temperatures.
With correct use, the patient’s temperature will be displayed in about 10 seconds for Model 670 and 4
seconds for Model 675. The instrument will beep to signal completion of the Normal mode temperature
cycle.
If the probe is left out of the storage channel after completion of a Normal mode temperature, the unit will
shut down after 5 minutes to conserve power. Simply replace the probe into the storage channel to prepare
for the next temperature.
Monitor Mode
The instrument can be switched to Monitor mode at any time by using the slide switch on the top right of the
unit. This mode will be indicated on the display by a capital M in the bottom right corner. Monitor mode
provides a direct readout of the probe temperature.
This mode of operation provides the ability to provide long term monitoring of a patient’s temperature.
Unlike a glass thermometer which is only peak reading, Monitor mode will follow a temperature as it rises or
falls.
The typical slow rise in temperature, when Monitor mode is used, is due mainly to the mouth temperature
slowly recovering from placement of the colder (room temperature) probe thus drawing it down. The probe
itself is actually very fast at rising to the temperature of its surroundings usually within a few seconds.
Because of this slow mouth recovery, 3 minutes is the recommended time to wait before recording a Monitor
mode temperature.
Monitor mode is also useful in testing the accuracy of the combined probe/instrument system when the
probe can be warmed to a known temperature, as with a Welch Allyn Model 9600 Calibration Tester or in a
water bath.
Note: The instrument will shut off automatically if the probe temperature remains below 28.9°C (84.0°F) for
more than 5 minutes.
If Monitor mode does not display expected temperatures or exhibits other problems, refer to the
Troubleshooting section on page 22.
Pulse Timer
The pulse timer provides a 30 second timer for general purpose use. This timer runs independently of other
thermometer functions and can be started and stopped at any time by pressing the Timer push-button.
If the timer does not work or exhibits other problems, refer to the Timer Problems section in the
Troubleshooting section.
Backlight/Temperature Recall
The backlight and temperature recall features are combined into one push-button.
The backlight provides a dim display light for use in dark rooms. It is usually not visible in well lit areas.
Shadowing the display with your hand is an effective way to see backlight operation. With the probe in the
storage channel, a momentary press of the backlight/recall button turns on the backlight and the last
temperature reading for 5 seconds. With the probe out of the storage channel, pressing the backlight/recall
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button turns on the backlight only for the duration of the button press and then at the end of a Normal mode
temperature, the reading will display with the backlight for 5 seconds.
Note: When a temperature is recalled, the mode in which it was obtained (Normal or Monitor) will be shown
independent of the present setting of the mode switch.
Note: When the instrument is in Monitor mode the last temperature memory is updated every second.
During the time between removing the probe from the patient, (at say 99.0 degrees) to inserting the probe in
the storage channel, it will have cooled. Therefore, the temperature stored in memory will be lower than the
patient’s temperature. This is not an issue in Normal mode as the memory is not updated after the
temperature is displayed.
If the backlight does not work or is showing other problems or if you cannot recall the last temperature, refer
to the Backlight/Temperature Recall Problems section in the Troubleshooting section on page 22.
F/C Switch
The temperature scale displayed can be changed at any time by use of the slide switch on the top of the
unit.
Note: A recalled temperature will be displayed in whichever scale is selected at the time of recall. This can
also be changed during display.
If the F/C switch does not change the scale of the displayed temperature, refer to the F/C Switch Problems
section in the Troubleshooting section.
Biotech Mode
Biotech mode provides the ability to query the following information:
1.
2.
3.
4.
5.
Battery voltage (total of all three).
Internal instrument calibration signal.
Instrument’s ability to detect probe type.
Software revision.
Display test.
Biotech mode is entered by the following steps:
1. Remove at least one battery.
2. Set the Normal/Monitor mode slide switch to Monitor.
3. While pressing and holding BOTH the Backlight/Recall and Timer switches, install the last battery.
4. Observe the display. The Monitor mode icon “M” will be flashing and the low battery icon will be on
steady. The timer will be operating. The number showing on the display is the total battery voltage. The
battery is considered acceptable if higher than 3.4 volts. New batteries should produce 4.5 volts or more.
Each thermometer is factory tested for accuracy down to a supply voltage of 2.9 volts. At about 3.2
volts, the low battery error E3.0 is triggered, the malfunction icon [X] is displayed, and temperature taking
is disallowed. This provides a margin of safety in preventing any inaccuracy in the results.
5. Press the Backlight/Recall button once to advance the display to the internal calibration signal. This
reading is generated by the instrument reading an internal precision fixed resistor as if it were a probe. If
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all of the A/D conversion electronics are functioning properly, this resistor will produce a reading between
36.7°C and 37.0°C (98.1°F and 98.6°F) inclusive.
6. Press the Backlight/Recall button once to advance the display to the probe type identification test. At
this point, probes can be installed or removed. Oral probes should produce the “OrL” display, while rectal
probes should produce the “rEC” display. When no probe is installed, the display is blank (except for the
flashing M). A calibration key, when plugged in at this time, looks like no probe is plugged-in.
7. Press the Backlight/Recall button once to advance the display to the software revision. The display
should show “r X.X” where “X.X” is a number such as 1.8. This can be helpful when discussing
operation with Welch Allyn customer support.
8. Press the Backlight/Recall button once to advance to the repeating display test. This is the same display
test as initiated when batteries are first installed. Each segment of the timer is incrementally turned on
while each segment of the remainder of the display is individually lit. Following this, all segments are lit
briefly and then the test repeats.
9. To repeat the sequence of displays in Biotech mode, press the Backlight/Recall button during the display
test when all segments are on.
10. To exit biotech mode at any time, switch to Normal mode. On exit, probe initialization will be started.
If you cannot enter the Biotech mode, refer to the Biotech Mode Problems section of the Troubleshooting
section on page 22.
Battery Life
Under normal use, battery life is expected to give up to 6,000 temperatures. This number is based on a
22.2°C (72.0°F) ambient temperature and 15% backlight use. Colder ambient temperatures, excessive
backlight usage, use of non-alkaline batteries, and other usage patterns can reduce battery life. Instruments
are shipped with fresh batteries, but we cannot guarantee full life from the first set of batteries due to
potential long storage times between shipping and actual use. Battery life can also be reduced by storage at
elevated temperatures.
If you are experiencing short battery life, refer to the Battery Life Problems section in the Troubleshooting
section on page 22.
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PREVENTATIVE MAINTENANCE
The following preventative maintenance is recommended to maximize uninterrupted service on the Model
670 SureTemp and 675 SureTemp 4 Thermometer:
Units which are in service on a regular basis should have the following preventative maintenance performed
every 6 months:
1.
Visually inspect the thermometer for physical damage which might cause future product failure.
2.
Clean the unit per instructions in your Directions for Use manual supplied with the thermometer and/or
per the instructions below.
3.
Perform the power up display test, startup display test and Model 9600 Calibration Testing procedure
found in the Model 9600 Operation Manual.
Units which are stored for an extended period and not used, should have the following performed every 12
months:
1.
Replace the batteries according to the procedures found in the Directions for Use manual.
2.
Perform the power up display test, Startup display test and Model 9600 Calibration Testing procedure
found in the Model 9600 Operation Manual.
Cleaning and Sterilization
Routine Cleaning
Clean the exterior of both the Model 670 or Model 675 instrument, the wall mount and the probe as needed.
Wipe all surfaces with a clean cloth dampened with warm water and a mild detergent, alcohol, or a
nonstaining disinfectant such as Sporicidin Spray and Towelettes or MetriSpray cleanser. Care should
be taken not to scratch the LCD faceplate. Make sure that the cloth is damp, but not too wet. Do not allow
cleaning solution to run inside the instrument. Never immerse the thermometer into the cleaning solution.
Never autoclave the thermometer or probe.
Sporicidin is a registered trademark of Sporicidin International (800) 424-3733.
MetriSpray is a trademark of Metrex Research Corporation (800) 841-1428.
ETO Gas Sterilization Procedure
When no other form of decontamination such as a germicidal wipe is acceptable, a low temperature, (not to
exceed 48.9°C (120°F)) ETO gas sterilization cycle may be used. Refer to your institution’s standard
operating procedure for the length of the cycle.
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This type of sterilization may cause some hazing of glossy plastic surfaces and should be used only when
absolutely necessary.
1. Ensure that the probe is removed from its storage channel and disconnected from the instrument.
2. Remove any probe covers from the probe and from the probe cover storage well.
3. Remove the batteries following the instructions in the Battery Removal and Replacement section
below.
WARNING: Leaving batteries in the thermometer during the sterilization procedure may present an
explosion hazard.
4. Wrap the thermometer in a standard sterilization type packaging such as the Baxter Tower Dualpeel
Sterilization Pouch.
5. ETO gas sterilize at a temperature not to exceed 48.9°C (120°F) and aerate.
6. Remove the sterilization packaging.
7. Before installing the batteries and probe, allow the probe and instrument to stabilize to room temperature
for at least one hour.
8. Reinstall the batteries following the Battery Removal and Replacement section, and verify a successful
self test.
9. Install the probe connector and insert the probe into the storage channel which will start the probe
initialization process.
10. Verify proper calibration of the thermometer and probe using the Welch Allyn Model 9600 Calibration
Tester.
Battery Removal and Replacement
1. Using a flat surface, lay the thermometer on its front case.
2. Remove the BATTERY ACCESS screw from the thermometer back case using a Phillips screwdriver.
3. Remove the battery door from the thermometer by sliding it out.
4. Remove the batteries.
5. Press either the Backlight/Recall switch or the Timer switch for approximately ten seconds to discharge
the electronics.
6. Install 3 new “AA” batteries according to the battery polarities marked inside the battery compartment.
Verify that the thermometer completes self-test, then goes blank. CAUTION: Incorrect battery polarity
may result in damage to the thermometer.
7. Reinstall the battery door.
8. Reinstall and tighten the BATTERY ACCESS screw.
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CALIBRATION TESTING
Calibration Key Procedure
Extract the probe and disconnect it from the thermometer. Set the Normal/Monitor switch to the Monitor
position and set the F/C switch to the F position. Insert the Calibration Key into the probe connector
receptacle on the thermometer. Insert a probe shaft into the probe storage channel and remove it to initiate
a temperature taking cycle. Wait for the display test and then observe the display. The display must read
between 97.1°F and 97.5°F inclusive for the calibration of the instrument to be correct. Remove the
Calibration Key and reinstall the probe connector plug. Then install the probe into the probe storage
channel. (This will initiate the probe self test.)
Note: This Cal Key test does not test the calibration of the probe. To do so requires the use of the Welch
Allyn Model 9600 Calibration Tester.
If the reading from the Cal Key is not within the specified range or you are having other problems with the
use of the Cal Key, refer to the Cal Key Problems section of the Troubleshooting section on page 22.
Model 9600 Procedure
The Model 9600 Calibration Tester provides a convenient means of testing the entire thermometer system
(instrument and probe). The 9600 must be warmed up and stable at one of the two available temperature
settings. The thermistor based instrument under test must be in Monitor mode and no probe cover loaded.
The probe is inserted into the small hole in the dry heat well of the 9600 and allowed to settle for a minimum
of 2 minutes to the final temperature. The reading on the thermometer must be within the range specified on
the 9600. Refer to the Model 9600 Operation Manual for complete instructions.
Note: All Welch Allyn and Diatek thermometers (thermistor and infrared ear thermometers can be checked
in the Model 9600.)
If you are having problems with the use of the Model 9600, refer to the Troubleshooting section in the Model
9600 Operation Manual.
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THEORY OF OPERATION
Technical Overview
The heart of the Model 670 and Model 675 is comprised of three custom integrated circuits which provide
most of the microcontroller and analog circuit functions. All control and display functions are governed by
the microcontroller (U2), all analog interfacing to the microcontroller, probe, horn and backlight is provided
by U1, and operating parameter data is handled by the EEPROM U3.
Probe resistance measurements are made by ratioing pulse widths which are generated by sequentially
switching in two calibration resistors and the probe thermistor. These pulse widths are measured by the
microprocessor which calculates the probe resistance. The actual probe temperature is then calculated from
the probe resistance.
pulse_timer
_factory_cal_sw
PULSE TIMER KEY
FACTORY
CALIBRATION
SYSTEM
CONNECTOR
clear_to_send
RXD
_blight_recall
BACKLIGHT/RECALL KEY
TXD
request_to_send
_monitor_mode
MONITOR/NORMAL SW
rs232_pwr
eeprom_ser_out
_celsius_mode
F/C SWITCH
eeprom_clock
EEPROM
eeprom_select
_probe_out
PROBE SWITCH
eeprom_ser_in
_eeprom_pwr
_horn_on
HORN
_heater_Q
PROBE
HEATER
_heater_C
_heater_tst
M38203
_heater_pwr
MICROCONTROLLER
LCD
DISPLAY
backlight_pwr
BACKLIGHT
ad_power
_ad_trigger
probe_ad_select
PULSE WIDTH
A/D
CONVERTOR
ptb_ad_select
hical_ad_select
lowcal_ad_select
LCD REFERENCE
batt_ad_select
_counter_gate
rectal_probe
PROBE
axillary_probe
4 MHZ CRYSTAL
FIGURE 3 - SYSTEM BLOCK DIAGRAM
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Probe Enhancements
The Model 670 and Model 675 series thermometers have the capability to detect probe type - oral vs. rectal.
This allows the oral temperatures to be as fast as possible (10 seconds in the 670 and 4 seconds in the 675)
by using different operating modes based on probe type. Rectal probes give a Normal mode temperature in
about 15 seconds for both models. This probe type recognition also allows the use of minor differences in
prediction parameters tailored to the temperature taking site to help increase speed over previous products.
The probe type is communicated to the thermometer by the use of shorting jumpers between ground and
two of the probe connector contacts.
In addition to the probe type enhancements, Model 670 and Model 675 probes have been improved for
thermal time constant (speed of response).
Model 675 oral probes incorporate a warming resistor in the tip to pre-warm the probe before placement in
the mouth, thus speeding response even further.
Probe Switch
The probe switch (S1) is activated by the probe shaft when the probe is installed or removed from its storage
channel. Placing the probe into the channel, pulls processor pin 23 high via R24. When the probe is
removed, this line is pulled low. This signal is also routed to test connector J3 pin 7 to allow automated
testing of this function during factory test. R24 allows this line to be pulled high or low at J3 during factory
test regardless of the actual switch position.
HINT/CAUTION: For the technician, J3 serves as a convenient set of “test points” to monitor proper
operation of all user switch functions, BUT BE CAREFUL WITH STATIC DISCHARGE! J3 TIES DIRECTLY
TO CMOS PROCESSOR INPUTS WHICH ARE EASILY DAMAGED BY STATIC DISCHARGE. FOLLOW
PROPER HANDLING TECHNIQUES.
Monitor Mode
The Monitor mode is selected manually by the Normal/Monitor mode slide switch (S3) on the top of the
instrument. This switch ties pin 10 on the processor (U2) either high or low for Normal or Monitor modes
respectively. This signal is routed through R14 and is also taken to the test connector J3 pin 4 to allow
automated testing of this function during factory test. R14 allows this line to be pulled high or low at the test
connector regardless of the switch position.
The actual probe temperature, as determined by the A/D conversion electronics, appears directly on the
liquid crystal display which is driven by the integral LCD driver in the microprocessor. See the Temperature
Measurement and Display section on page 16 for a description of the A/D operation.
The displayed temperature range (for any mode) is limited to 28.9°C to 42.2°C (84.0°F to 108.0°F).
Normal Mode, Model 670
The shape of the rising temperature curve is monitored and a continuously computed correction factor is
added to the actual probe temperature. The temperature cycle is terminated and the temperature is
displayed when the predicted temperature remains stable.
If the thermometer does not detect a rise of two degrees above ambient within 30 seconds of removing the
probe from its holder, it will automatically switch to Monitor mode.
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Normal Mode, Model 675
The Oral probe is pre-warmed using a pulse width modulation (PWM) controller to 33.9°C (93°F) upon
extraction from the storage channel. When the probe is first extracted and colder than 33.9°C, the pulse
widths are at a maximum percentage ON vs. OFF to warm the probe quickly. When the probe reaches
33.9°C, the pulse widths narrow to a duty cycle just enough to maintain temperature. When the probe is
placed in the mouth, the heat supplied by the mouth makes the pulse widths reduce to zero. This reduction
to zero (and the probe being at least up to 33.1°C) triggers the start of the prediction algorithm.
The shape of the rising temperature curve is monitored and the best fit to a curve is found. When the curve
fit is stable, the final predicted temperature is displayed.
If the prediction criteria explained above are not met within 15 seconds of starting the prediction process, it
will automatically switch to Monitor mode.
If the ambient temperature is above 33.9°C (93.0°F) the unit will automatically switch to Monitor mode.
Rectal probes are not prewarmed and the operation is similar to that in the Model 670.
Power Supply
Power is drawn from the three “AA” alkaline cells directly to the circuit electronics. The voltage from the
batteries is unregulated but filtered for noise by capacitor C9. The power supply voltage will range from
about 4.8 volts with new batteries to 3.2 volts at shut down. The thermometer has two low battery voltage
indicators. The first is a warning that batteries are getting low and is indicated by the battery icon flashing in
the display. This begins when the batteries fall to about 3.4 volts. Accuracy is not effected during low
battery warning indication. When the batteries fall to approximately 3.2 volts, the low battery error condition
is defined to exist. Operation is halted and the E3.0 error message is displayed.
At this point, the batteries must be replaced and the thermometer electronics reset. See the Reset
Self/Tests section on page 16 and in the Operational Characteristics section on page 2.
Microprocessor Usage
Inputs to the microprocessor include LCD voltage regulator lines (pins 6,7 and 8), user switch lines (pins 10,
11, 23, 39 and 40), A/D done output signal (pin 13), low battery signal (not used by software)(pin 14), probe
warmer self check lines (pins 15 and 16), probe type identification lines (pins 17 and 18), serial port lines
(pins 19 and 22), EEPROM U3 data line (pin 25), factory calibration mode select line (pin 26), reset line (pin
27), slow clock (not used) (pin 28), and the 4MHz microprocessor clock (pin 30).
Outputs from the microprocessor include LCD driver lines (pins 1 through 5, 57 through 72, and 74 through
80), horn control line (pin 12), serial port lines (pins 21, 24 and 53), slow clock (not used) (pin 29), the 4MHz
microprocessor clock (pin 31), battery voltage measure line (pin 41), A/D control lines (pins 42 through 45, 51
and 56), EEPROM control lines (pins 46, 47,48 and 50), LCD voltage regulator control line (pin 49), backlight
control line (pin 52), probe warmer control lines (pins 54 and 55).
Reset/Self Tests
Upon battery installation, (assuming that the electronics has been discharged sufficiently by pressing a user
button with batteries removed) the microprocessor receives a power up reset signal from the components
associated with the reset line U2-27. During short duration power dropout capacitor C1 is discharged quickly
through D6. When power is applied continuously, C1 is charged slowly through R7 providing an active low
reset to the microprocessor.
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When the reset signal is complete, the microprocessor launches a series of self checks which include RAM
test, ROM test, EEPROM test, instruction set test, self calibration tests (PTB test, hi cal, low cal), probe
warmer circuitry tests, probe test, battery voltage test and ambient temperature test. Any failures here will
cause a specific error code to be displayed to assist debugging.
Microprocessor Clock
The clock for the processor is generated by X1. This is a single 3 pin ceramic resonator with internal
capacitors running at 4 MHz. The processor U2 drives this component into oscillation by incorporating an
internal inverter.
[The other clock circuitry (if shown on schematic) consisting of X2, R9, C4 and C6 is no longer used.]
Temperature Measurement and Display
The thermometer uses probes which incorporate negative temperature coefficient thermistors. When the
temperature of the probe is increased, its electrical resistance decreases. Earlier products (Model 600,
Model 650) use “10K” thermistors which means that, at room temperature (25°C), their value is
approximately 10 Kohms. Model 670 and 675 use “20K” thermistors so they are approximately 20 Kohms at
room temperature. At 37°C (patient temperatures) they are near 12 Kohms. The change in resistance is
nonlinear with temperature and an equation describing this curve is programmed into the thermometer.
The thermometer contains three high precision calibration resistors (0.1% tolerance) R3, R5 and R8. Their
values are programmed into the instrument so that A/D conversions from these can be done to “calibrate”
the electronics. This allows results from the unknown probe resistance to be compared to the known
resistance. These three resistors are referred to as “hi cal”, “low cal” and “PTB” resistors. They are
equivalent to temperatures in that if the probe were at a high temperature 41.6°C (106.8°F), its resistance
would equal the hi cal resistor value. Similarly if the probe were at a low temperature 33.8°C (92.9°F), its
resistance would equal the low cal resistor value. The PTB resistor is in the middle of the range and
equivalent to 36.8°C (98.3°F). Use of these resistors in the A/D process allows the probe resistance
readings to be “ratioed” against known resistance readings, and thus “absolute” readings, which can be
affected by drift in the electronics due to aging and temperature, are eliminated.
The actual A/D conversion consists of converting resistance to a timed pulse width. The components
involved are C2 (the timing capacitor), Q11 (the constant current transistor), any one of R3, R5, R8 or the
actual probe resistance, and the associated FET transistors Q4, Q5, Q6 or Q10.
Due to U1 design, on power up R26 and R29 bootstrap U1 to begin the charge of C2. Once a small voltage
is developed on C2, U1 takes over and maintains C2 at 2.4 volts via pin 7 of U1. When an A/D conversion is
to start, prior to the trigger from the processor, it turns on one of the four FETs. This establishes a constant
current through the associated resistor. The current flowing is supplied from U1 pin 7 while maintaining its
voltage at 2.4 volts. Throughout the A/D process, U1 pin 4 is held at 1.2 volts. This means that while
current is flowing through Q11, its emitter sits at 0.6 volts. Since this is a constant voltage, the current
through the selected resistor and FET is also constant. The next event is to trigger the start of the pulse
measurement which occurs via processor control into U1 pin 5. This makes U1 pin 7 go to high impedance
ending its supply of current for the selected resistor. Therefore current must now be supplied by C2. Since
it is still a constant current situation, C2 discharges linearly with time. Its voltage is monitored by an internal
comparator in U1 and when it drops to 1.2 volts the A/D OUT line (U1 pin 2) goes active stopping the timer in
the processor. The constant current value is inversely proportional to the resistance value selected so that
small resistance values produce high currents and therefore fast discharges. Since small resistance’s are
related to high temperatures, short pulse widths are also related to high temperatures. L2 is in series with
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the discharge current but constitutes a very small constant DC resistance so it has no effect on results. Its
only purpose is for RFI suppression. C3, C10, C11, C12 and C13 are also only for RFI, and ESD purposes.
In Monitor mode a calibration cycle, where each of the fixed resistors is measured by the A/D function, is
performed once every second. In Normal mode a calibration cycle is performed once at the beginning of the
temperature prediction process.
Battery Voltage Reading
Battery voltage reading capability has been added over previous products providing necessary information to
the probe warming function and also providing the enhanced two stage low battery indicator.
When not in use, the BATT AD SELECT line (U2 pin 41) is held low. This keeps diode D9 reverse biased
and thus R28 has no effect on the normal A/D function during temperature measurements.
When battery voltage is to be read, this line is brought high by the processor (to whatever the battery voltage
happens to be). This voltage across R28 establishes a current flow. (The common point of R28 with the
other resistors is at 0.6 volts - because Q11 base is at 1.2 volts). This current flowing through R28 increases
the A/D pulse width since this much current is not needed from C2. R5 is always selected for battery voltage
reading since it normally produces the shortest pulse. If battery voltage is low, the current supplied via R28
is low and therefore the pulse width is lengthened only slightly. If the battery voltage is high, the pulse width
is lengthened more. Knowing the standard pulse width from R5 allows the instrument to relate this
lengthening of pulse width to the supply voltage.
A/D Power Control
When A/D conversions are not needed, power is saved by shutting down U1 via the A/D PWR line on U2 pin
56. R27 serves as a current limiting resistor and establishes the low power draw for U1’s internal current
sources.
This A/D Power line is also routed to R11 and R13 for probe detection. This provides a power saving
function so supply current is not drawn through these resistors when probe detection is complete.
Probe Detection
Upon power reset or when a new probe is first installed, the thermometer performs a probe initialization
process. Probe type is first detected and then if it is a Model 675 and an oral probe, its warming
characteristics are determined. Model 670 thermometers do not warm probes so warming characteristics
are not tested on any type of Model 670 probe. No rectal probes are warmed, so warming characteristics
are not tested in either instrument on these probes.
The instrument keeps track of whether a probe is installed or not. This is accomplished by the fact that to
unplug a probe, the shaft must first be withdrawn from the storage channel. This wakes up the thermometer
which then turns on A/D power. This activates the probe type lines U2 pins 17 and 18 via R11, R12, R13
and R25. When the probe connector is removed, these lines are pulled high and a “no probe” logic is
detected. (The Cal Key is also “no probe” logic so the software upon seeing no probe actually reads the
probe resistance and if it falls well outside the Cal Key value, determines that indeed there is no probe
attached.) Upon determining that the probe has been removed, a software flag is set in RAM indicating the
probe has been removed. (RAM contents are not lost when the processor “goes to sleep.”) With no probe
installed, the unit “goes to sleep” and turns off the clock and the A/D power line to save battery power.
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Probe connector installation does not “wake” the instrument up. When the probe shaft is stowed, the probe
switch places voltage on U2 pin 23 via R24. This “wakes up” the processor which then reads the RAM flag
and sees that the probe logic lines are indicating a probe is connected. This situation triggers a probe
characterization routine as described in the Probe Warming section.
The probe type is determined by the probe logic lines at J1-B and E. Oral probes pull both lines low. Rectal
probes pull only J1-E low.
Probe Warming (675 Oral probes only)
Probe characteristics vary somewhat due to normal production process variations. It is desirable to warm
the probe as efficiently as possible from a time--to--ready standpoint and from a temperature stability
standpoint when the probe is up to temperature.
The probe warming process is a closed loop feedback control system incorporating PWM (pulse width
modulation) control. To establish proper control parameters, the probe under control must be characterized.
The probe characterization process begins with a battery voltage reading. The battery voltage is needed in
the calculations to determine how much power will be applied to the probe during the 200mS test pulse.
After the battery voltage is read, the probe temperature is read once every 200 mS until the temperature is
found to be not changing.
Once a stable temperature is determined a 200 mS test pulse of power is applied to the probe via the
warming circuitry. The probe temperature change resulting from this pulse is used to determine parameters
needed for the PWM algorithm. This completes the probe characterization process.
The warming circuitry consists of Q7, Q8, Q9, R16, R18, R20, R21, R22, R23, C7, C8, D7, L1 and the
resistance in the probe connected to J1-D and J1-F. Power is applied to the probe connection only when
both Q7 and Q9 are turned on. When this occurs, both feedback lines to the processor (U2 pins 15 and 16)
are pulled high indicating proper operation. A fail safe hardware shut off circuit is incorporated consisting of
C8, D7, Q8 and R22. This circuit will shut off power to the probe if the software fails to refresh this circuit.
This prevents overheating due to any software errors leaving the warmer circuit on continuously.
At the start of a warming pulse, the processor drives both heater control lines (pins 54 and 55) low. This
turns on all three transistors Q7, Q8 and Q9. Q8 is turned on because the voltage across capacitor C8
cannot change instantly. Its positive side goes low when its negative side is pulled low by the processor.
Since Q9 E and B are pulled near the positive rail and Q8 B and E are pulled near the negative rail, the base
current from Q9 flows through R16 and mostly into Q8, but some current flows through R22 to satisfy the
diode drop across Q8 E to B. This current and Q8 base current flow into C8 charging it. As it charges, the
voltage rise eventually shuts off Q9.
This hardware shut off is only allowed to progress to completion during factory test and each time an oral
probe is installed as part of the instrument self test process. The thermometer checks that the hardware
shut off has occurred within one second of turn on.
Normal probe warming is controlled by the software and if the probe is well below the control temperature of
33.9°C (93°F), the pulse widths are at a maximum. Every 100 mS the hardware shutoff circuit is briefly
refreshed by the processor driving its pin 54 high. This momentarily shuts off power to the probe while
discharging C8 into the positive supply through D7.
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Once the probe has been brought near 33.9°C (93°F), the pulse widths are reduced to maintain this
temperature. This is when the display switches from the all segments display test to “OrL” indicating that the
unit is ready for placement in the mouth.
Note: Do not confuse this with the displays during probe characterization, where “OrL” is indicating that
characterization is in progress with the probe in the holder.
R20 and R21 in combination with R23 serve as pull down resistors ensuring that the processor feedback
lines (U2 pins 15 and 16) go low immediately upon warmer component shut off. L1 and C7 serve as RFI
suppression components.
Note: On Model 670, some of the components in the warmer circuit may be installed but they are not used.
Q7 is NEVER installed at the factory and should never be installed on Model 670. Installation of Q7 will NOT
activate the warmer on Model 670 and will cause a malfunction error code to result, inhibiting further use of
the instrument.
EEPROM
U3 is an Electrically Erasable Programmable Read Only Memory (EEPROM) incorporating a serial data
communication interface with the microprocessor. Data is clocked synchronous with the “serial clock” input
on pin 2. Data into the EEPROM goes into pin 3. Data out of U3 comes out on pin 4. Pin 1 is the chip
select line. Pin 5 is the ground pin but is tied to a processor port line. This allows power to be saved by
driving all EEPROM pins to the positive supply which reduces power consumption to zero for this part. The
EEPROM is therefore only turned on when needed, which is only during power up routines. Most of the time
the EEPROM data is stored in RAM, which remains even when the processor enters sleep mode (as long as
battery power is available). Therefore, unless a software error has occurred, the EEPROM is only read upon
installation of new batteries. The EEPROM is downloaded initially at the factory with operating parameter
data giving the thermometer most of its operating characteristics such as factory test system parameters,
Normal mode prediction parameters, warmer control parameters, and numerous miscellaneous parameters
setting operating temperature limits, times, warning levels, etc. The EEPROM cannot be changed in the
field.
Liquid Crystal Display
The LCD has 4 backplane lines (U2 pins 2-5) and 24 segment lines (U2 1, 57 - 72, 74 - 80). The LCD fluid
thresholds require a regulated set of voltages at 1.2, 2.4, and 3.6 volts. These are supplied to processor
pins 6, 7 and 8 from the diode stack D1, D2, D3, D4, D5 and related components Q3, R4 and R17. Circuit
operation is initiated by the processor pulling pin 49 low. This draws the emitter of Q3 low and thus the base
of Q3 to .6 volts above ground. This voltage across R4 establishes a current through the diode stack. Any
change in power supply voltage is absorbed to a great extent by R17 and the Q3 collector connection
keeping the voltages across the diodes relatively constant.
The LCD glass is electrically tied to the display PCB via two elastomeric connectors sandwiched and
compressed between the glass and the PCB by the frame. This assembly, if taken apart, cannot be
reassembled without replacing the frame.
Backlight/Temperature Recall
The backlight is an electroluminescent style flat panel lamp residing directly under the LCD.
An oscillator is required to convert battery DC voltage to an AC voltage of about 80 volts and 300 Hz.
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The momentary backlight switch (S4) pulls processor pin 39 low. R19 acts as a pull up to return this line
high when not in use. This line is also run to test connector J3 pin 6 to allow automated testing of this
function during factory test.
The processor active high signal is sent out on U2 pin 52 to U1 pin 12 where it is inverted and buffered. This
signal coming out of U1 pin 13 pulls through diode D8 and flex strip J2 pin 21 to the display board mounted
oscillator. The oscillator consists of Q1, Q2, C5, R1, R2, T1 and the lamp itself.
If the thermometer is not in the process of taking a temperature, the Backlight/Recall switch will wake up the
thermometer and display the last recorded temperature.
Horn
The horn is activated at the start of a temperature taking cycle, at the end of a Normal mode temperature
cycle, during timer operation at 0, 15 and 30 seconds, and for various error conditions.
A short duration high pitch single beep is indicative of normal operation. A short duration lower pitch double
beep is used to indicate errors such as switching from Monitor mode to Normal mode during a temperature
cycle.
The horn is a piezoelectric ceramic resonator driven by a processor square wave buffered through U1. The
horn control signal comes from U2 pin 12 and enters U1 pin 3 where it is buffered and inverted and sent out
on pin 1 directly to the horn LS1.
F/C Switching
The F/C switch (S2) sets the processor pin 11 via resistor R6 high or low for F or C respectively. This line is
also run to the test connector J3 pin 3 to allow automated testing of this function during factory test. R6
allows this line to be pulled high or low at J3 during factory test regardless of the position of the switch.
Timer
The 30 second timer is started or stopped at any time by pressing the Timer switch (S5). This pulls
processor pin 40 low momentarily. This line is also run to test connector J3 pin 5 to allow automated testing
of this function during factory test. Resistor R10 returns this line high when not in use.
ERROR CODES
Error codes fall into three categories. Transitory, Recoverable and Non-Recoverable.
Transitory errors are generated by external events and are not errors generated by the thermometer. They
do require that temperature measuring be inhibited until the error is cleared. There is no limit to the number
of times a transitory error can occur. All probe problems are considered by the thermometer to be external
events and are therefore classified as transitory.
Recoverable errors are generated from internal test failures, which are non-catastrophic and require that
temperature measuring be inhibited until the error is cleared. A recoverable error will be promoted to a nonrecoverable error if it occurs four times sequentially. After displaying the error code and any appropriate
icon, the instrument will reset itself and attempt to resume normal operation. After the fourth attempt to clear
itself, the error becomes non-recoverable.
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Non-recoverable errors are generated from internal test failures that are catastrophic (or from promoted
recoverable errors). The error code and any appropriate icon will be displayed along with the “[X]”
Instrument Malfunction icon.
The only way to continue at this point is to reset the electronics by removing the batteries.
NOTE: The error codes E2.1, E2.3, E3.0, E3.1, E3.2 and E4.1 can sometimes be caused by a faulty probe.
It is advisable to remove probe completely from instrument and check functionality as described in the Setup
section on page 4 before assuming an instrument problem instead of a probe problem. If another probe is
available, this can prove useful in tracking down the source of the problem.
Error Code Table
NUMBER
ERROR TYPE
E0.0
E0.1
E0.2
E0.3
E0.4
E0.5
E0.6
E0.7
NON-RECOVER
NON-RECOVER
NON-RECOVER
NON-RECOVER
RECOVERABLE
NON-RECOVER
RECOVERABLE
RECOVERABLE
E1.0
E1.2
E1.3
E1.4
E1.5
E1.6
E1.7
E1.8
NON-RECOVER
NON-RECOVER
NON-RECOVER
NON-RECOVER
NON-RECOVER
NON-RECOVER
NON-RECOVER
NON-RECOVER
E2.0
E2.1
E2.2
E2.3
E2.4
RECOVERABLE
RECOVERABLE
RECOVERABLE
RECOVERABLE
RECOVERABLE
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DESCRIPTION
System Hardware Errors
Stack ram test error
Internal RAM test failed
Internal ROM check sum failed
Instrument error
EEPROM check sum error
RAM check sum error
EEPROM busy too long
EEPROM address write error
Exception Errors
External interrupt 0. (INT0.)
Transmitter interrupt (TXD)
Timer Y interrupt (TYINT)
Timer 2 interrupt (T2INT)
External counter interrupt 0. (CNTR0.)
Timer 1 interrupt (T1INT)
Serial I/O
Software break
A/D Converter Errors
Low cal. resistor pulse width error
Hi cal. resistor pulse width error
PTB resistor pulse width error
Probe pulse width error
Could not determine cause
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Error Code Table (continued)
E3.0
E3.1
E3.2
NON-RECOVER
RECOVERABLE
TRANSITORY
E4.0
E4.1
RECOVERABLE
RECOVERABLE
E5.0
E5.1
E5.2
E5.3
E5.4
E5.5
E5.6
E5.7
RECOVERABLE
RECOVERABLE
RECOVERABLE
TRANSITORY
TRANSITORY
RECOVERABLE
RECOVERABLE
RECOVERABLE
E6.1
E6.2
E6.3
E6.4
RECOVERABLE
RECOVERABLE
RECOVERABLE
TRANSITORY
E9.9
RECOVERABLE
System Functional Errors
Low battery error
PTB test error
Outside operating temp range
Math Errors
Floating point over flow
Log of zero is undefined
Warmer and Probe Errors
Q warmer transistor failure
C warmer transistor
Warmer protection circuit failure
Probe warmer not warming
Probe missing or thermistor failure
Warmer circuit failure
Warmer overheated
Warmer watch dog time out
Serial Communications Errors
Serial overrun error
Serial framing error
No data time out error
Transmit buffer overflow (transmit only, no display)
System Software Errors
Undefined software state
TROUBLESHOOTING
Many thermometer operational parameters can be tested for proper operation before the unit is taken apart
and without needing any tools. Refer to the Operational Characteristics section on page 2 and in
particular to the Setup and Biotech Mode sections for guidance on preliminary checks.
If the trouble seems to be calibration related, refer to the Calibration Testing section on page 12.
If these sections do not prove useful in resolving the problem and you are sure that the instrument is not
performing properly, the following sections should guide you through the debugging process given the
proper tools and equipment.
Equipment Required
Most operations can be performed with standard tools and meters. A #1 Phillips screwdriver suffices for all
instrument screws.
A standard lab 3.5 digit digital multi-meter (DMM) will provide sufficient accuracy for a host of tests. A
needle tipped pair of probes is recommended.
For particularly difficult tasks, an oscilloscope is sometimes the only way to analyze high speed signals, but
is not generally required.
Standard electronics tools and supplies for small surface mounted and through hole component rework will
be needed to perform any electronics repairs. Some surface mounted components are extremely small and
present a challenge for rework by hand. A light touch, tweezers, sharp soldering iron tip and low heat (#7
tip) is recommended.
22
®
®
SureTemp Model 670/SureTemp 4 Model 675
Technical Manual
Power and ground are available at the end terminals of slide switches S2 or S3.
Terminology
Many standard abbreviations are used in this section (and elsewhere):
PCB
printed circuit board (the board itself)
LCD
PCB
PCB holding the display assembly
PCA
printed circuit assembly (the board
with all its components)
DMM
Digital Multi-Meter
main
PCB
large PCB holding the
microprocessor
O-Scope
Oscilloscope
LCD
Liquid Crystal Display
Component Reference Designators:
C
capacitor
Q
transistor
D
diode
R
resistor
E
test point
S
switch
J
connector jack
T
transformer
L
inductor
U
integrated circuit
P
connector plug
X
crystal, resonator
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SureTemp Model 670/SureTemp 4 Model 675
23
Welch Allyn, Inc.
Troubleshooting Table
SYMPTOM
POSSIBLE CAUSE
PROCEDURE
No operation
Dead batteries, no
batteries, battery missing,
battery incorrectly installed
Refer to Battery Replacement section
on page 11. Check that all batteries
are installed in proper direction.
Reset electronics (see Instrument
Reset/Self Tests section on page 4)
Refer to Biotech Mode section on page
8 and enter Biotech mode to measure
battery voltage as seen by electronics.
Display problems
24
Broken battery wire
Open instrument case, install batteries,
check for voltage on main PCB at
battery wire connections.
Circuit short preventing
operation.
Remove batteries, press backlight
switch for 1 second, set DMM to
Ohms, measure resistance of
electronics at battery contacts (“+” to
bottom right corner, “-” to top left
corner) Resistance should climb to
more than 2 Megohms as C9 charges.
Failed component.
Check oscillator at U2-31 for 4 MHz
sine wave. If not present, suspect X1
or U2.
LCD frame loose.
Check that all 6 white plastic rivets
(heat staked pins) for the LCD frame
are tight and not broken on either side
of PCB. The frame should not be
lifting off of PCB.
Dirty LCD elastomeric
conductor strips.
Have a new LCD frame handy.
Remove old one by breaking plastic
pin rivets. Clean LCD elastomeric
strips, LCD glass contacts, and PCB
contacts with lint proof cloth dampened
with alcohol.
®
®
SureTemp Model 670/SureTemp 4 Model 675
Technical Manual
Troubleshooting Table (continued)
SYMPTOM
POSSIBLE CAUSE
PROCEDURE
Display problems
(continued)
Broken/shorted flex strip
cable.
Check continuity of all 30 lines. Assure
continuity with flexing of strip.
Check for shorts between adjacent
lines at both ends.
No beeper sound
No Timer function
®
Failed component in LCD
voltage regulator circuit.
Check voltages on U2-6, 7 and 8 for
about 3.6, 2.4 and 1.2 volts
respectively with LCD active.
Cracked LCD.
Inspect LCD for hairline cracks
especially in corners.
Short circuit or open LCD
lines.
Check continuity from U2 through to
LCD board. Check for shorts between
adjacent processor LCD pins.
Microprocessor failure.
Check for improper soldering of pins,
crystal operation on O-scope, proper
reset.
Broken horn wire
Inspect horn wires for proper solder
Defective horn
Replace horn
Broken connection
Check continuity from U2-12 to U1 3.
From U1-1 to red horn wire. From U114 to black horn wire.
Defective U1
Factory only repair.
Defective U2
Replace U2
Defective Timer switch.
Check J3-5 for proper switch function.
Broken trace.
Check U2-40 for proper switch
function.
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SureTemp Model 670/SureTemp 4 Model 675
25
Welch Allyn, Inc.
Troubleshooting Table (continued)
SYMPTOM
POSSIBLE CAUSE
PROCEDURE
Timer segment missing.
LCD problem.
See Display problems section.
No Backlight/Recall
Defective backlight/Recall
switch
Check J3-6 for proper switch function.
Broken trace.
Check U2-39 for proper switch function
also J2-21. With backlight off, all of
oscillator parts (Q1, Q2, R1, R2, C5
and T1(primary) should be at Vcc.
Defective Component
Check U1-12 and 13, check D8, Q1,
Q2.
Unit switched to Monitor
mode.
If unit is in Monitor mode (whether by
the user switch or automatically), the
stored temperature is the last one seen
by the instrument. This is usually
lower than the patient temperature
since the probe drops in temperature
after removal from the patient and
before insertion in the storage channel.
Probe withdrawn or
batteries replaced.
Last stored temperature is erased by
starting next temperature cycle when
probe is extracted from storage
channel.
Recalled temperature is
not correct.
Battery replacement erases last stored
temperature.
F/C switch problems
Probe: Wrong type
displayed.
26
Defective switch
Check J3-3 for proper switch function.
Broken trace
Check U2-11 for proper switch
function.
Missing A/D power to R11
and/or R13
With no probe installed, check that
probe connector pins J1-B and E are
both pulled high when any function is
active (recall or timer)
®
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SureTemp Model 670/SureTemp 4 Model 675
Technical Manual
Troubleshooting Table (continued)
SYMPTOM
POSSIBLE CAUSE
PROCEDURE
Probe: Wrong type
displayed (continued)
Incorrect wiring of probe
Oral probes should have a short
between pins B, E and F. (refer to
instrument PCB designators for probe
pin definition.)
Rectal probes should have a short
between pins E and F but open
between pins B and E or F.
Replace with new probe.
Probe: Plugged in but
no display
Probe not characterized
A new probe must be installed and left
in the storage channel until the display
goes blank. If probe is extracted
during characterization, display goes
blank and operation is halted.
Normal/Monitor Mode
switching problems
Ambient above 33.9°C
(93.0°F)
Causes auto switch to Monitor mode.
Switched to Monitor mode
before probe in mouth.
If 30 seconds pass after ready in
Normal mode, unit switches to Monitor
mode.
If probe is still cooling from a previous
temperature and used immediately, it
might sense ambient to be above
33.9°C (93.0°F).
Defective switch
Check J3-4 for proper switch function.
Check U2-10 for proper switch
function.
Cannot enter Biotech
Mode
®
Improper switch setting.
Normal/Monitor switch must be in
Monitor position.
Improper switch setting.
Must hold BOTH push-button switched
closed while installing battery.
Failed component, broken
trace.
Check proper switch operation. Refer
to F/C and Backlight/Recall switch
troubleshooting.
®
SureTemp Model 670/SureTemp 4 Model 675
27
Welch Allyn, Inc.
Troubleshooting Table (continued)
28
SYMPTOM
POSSIBLE CAUSE
PROCEDURE
Battery Life Problems
Excessive backlight use
Backlight draws significant current.
Normal battery life calculations assume
only 15% backlight usage.
Dead cell
If cell voltage is down significantly in
only one cell, this battery is defective.
All batteries are drained at the same
rate by the instrument.
First Set Shelf Life
Due to possibly long stocking times
between fabrication and end use, the
first set of batteries may have reduced
life.
Cal Key doesn’t activate
thermometer
Probe switch not also used.
M670/M675 thermometers (unlike
M600) need probe switch activated
before they will start. Use a probe
shaft in storage channel temporarily to
start Cal Key process.
Cal Key shows OrL,
rEC, or ALy
Defective Cal Key
Replace Cal Key
Cal Key shows only
“°F”.
Normal/Monitor switch in
wrong position.
Normal/Monitor slide switch must be in
Monitor position to see a Cal Key
temperature. (Or wait 30 seconds for
auto switch to Monitor mode.)
Monitor mode
temperature reading too
low.
Probe malfunction
Change probe.
Test calibration of entire system
(instrument and probe) with the M9600
Calibration Tester.
Instrument malfunction.
Check calibration with Cal Key.
Improper placement of
probe.
Probe must be under the tongue and
as far back as possible into the
sublingual pocket.
Temperature not stable.
Allow three minutes for Monitor mode
reading to stabilize in mouth.
®
®
SureTemp Model 670/SureTemp 4 Model 675
Technical Manual
Troubleshooting Table (continued)
SYMPTOM
POSSIBLE CAUSE
PROCEDURE
Monitor mode
temperature reading too
high
Probe malfunction
Change probe or test calibration of
entire system (instrument and probe)
with the M9600 Calibration Tester.
Instrument malfunction.
Check calibration with Cal Key.
Probe malfunction.
Recharacterize probe. (remove
completely from instrument and reinstall.)
Normal mode
temperature reading too
low.
Or change probe.
Or test calibration of entire system
using 9600.
Normal mode
temperature reading too
high.
Instrument malfunction
Check calibration with Cal Key.
Improper placement of
probe.
Probe must be under the tongue and
as far back as possible into the
sublingual pocket.
Probe malfunction.
Recharacterize probe. (remove
completely from instrument and reinstall.)
Or change probe.
Or test calibration of entire system
using 9600.
®
Instrument malfunction
Check calibration with Cal Key.
Improper technique.
Movement in mouth after insertion and
before final temperature is displayed
can cause high readings. Place probe
quickly into sublingual pocket and hold
still.
Improper technique.
Do not place probe in mouth until
display is showing “OrL”.
®
SureTemp Model 670/SureTemp 4 Model 675
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Welch Allyn, Inc.
FIELD SERVICEABLE REPAIRS
Repairs are considered field serviceable if the repair will not alter the calibration or proper operation of the
instrument. Recalibration requires a computer-based system and is normally performed at the factory.
All probes designed to work with the thermometer are fully interchangeable.
All components in the Model 670 and Model 675 except U1 and U3 can be replaced without effecting
instrument operation or calibration. Some minor changes to the exact calibration point will be caused by
changing R3, R5 and R8, but as long as the proper type and tolerance resistors are used (0.1%, as supplied
by Welch Allyn), the unit will remain within specifications.
Replacement of the LCD frame is somewhat difficult due to the need to “heat stake” the assembly while
under pressure to assure proper compression of the elastomeric connector. The LCD frame once removed
cannot be re-used.
Note: Do not glue the LCD frame to the display PCB if the frame pins are broken. This will destroy the
display PCB. Replace the LCD frame with a new LCD frame.
FACTORY SERVICEABLE ONLY REPAIRS
Because of programming requirements and characterization requirements, if problems are traced to U1 or
U3, the unit must be returned to the factory or properly equipped service center for repair. Very specialized
custom test equipment is required to perform recalibration and characterization after replacing U1 or U3.
FIELD SERVICEABLE PARTS
All parts are serviceable by qualified technicians except for the EEPROM (U3) and the Monochip (U1).
30
®
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SureTemp Model 670/SureTemp 4 Model 675
Technical Manual
THERMOMETER DISASSEMBLY
Please note that if your thermometer is within the warranty period, you should return the unit to an
authorized service representative for servicing; failure to do so will invalidate the warranty.
WARNING: This instrument contains microelectronic devices which are highly susceptible to damage by
static discharge. Use proper handling and grounding techniques while working on the internal electronics.
1. Withdraw the probe from the probe storage channel.
2. Unplug the probe connector from the thermometer.
3. Peel the °F-°C / NORMAL-MONITOR label from the top of the thermometer.
4. Lay the thermometer on its front case.
5. Remove the BATTERY ACCESS screw from the thermometer back case.
6. Remove the battery door from the thermometer.
7. Remove the batteries.
8. Remove the other three screws from the thermometer back case.
9. Carefully remove the thermometer back case, keeping the thermometer electronics assembly and midframe in the front case.
10. Remove the neck strap or neck strap pins.
11. Remove the two internal screws securing the display board to the thermometer front case.
12. Remove the electronics assembly by gently lifting the mid-frame and display board from the front case.
The electronics assembly can be removed from the mid-frame by carefully desoldering the battery wires
and horn wires from the main PCA, gently pulling outward on the two plastic tabs securing the PCA at
the top of the mid-frame, and carefully sliding the main PCA towards the top of the mid-frame until the
lower edge of the PCA clears the two retaining tabs on the mid frame.
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SureTemp Model 670/SureTemp 4 Model 675
31
Welch Allyn, Inc.
FIGURE 4 - THERMOMETER ASSEMBLY DRAWING
32
®
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SureTemp Model 670/SureTemp 4 Model 675
Technical Manual
Item
Model 670
Model 675
(if different from
Model 670)
20952-100
Description
Qty
Electronics Assembly
1
1
20952-000
3
25088-001
Case Front
1
4
25089-001
Case Back
1
5
25090-100
Mid-Frame
1
6
25091-001
Battery Door
1
7
25103-000
Window, Display
1
8
53009-000
Battery. Alkaline “AA”
3
10
70082-001
Blank Overlay
1
11
70082-000
Label, Serial Number
1
12
70158-200
Label Set
1
14
70437-000
Label, Serial Number
2
16
80013-001
Wire, 26 AWG, Stranded - Black
0.3 Ft
17
80013-0002
Wire, 26 AWG, Stranded - Red
0.3 Ft
18
30056-0000
Pin, Strap
2
20
83021-0000
Screw, Thd-Roll #4 X 1/4 Philips
2.
21
83035-000
Screw, Thd-Roll #4 X 7/8 Plastilok
1.
22
83036-0000
Screw, Mach 4-40 X 1/16 Philips
11
23
83037-000
Screw, Thd-Roll #4 X 3/4 Plastilok
2.
24
58411-000
Battery Contact, Common
2
25
58412-000
Battery Contact, Positive
1
26
58413-000
Battery Contact, Negative
1
70158-300
FIGURE 4 - THERMOMETER ASSEMBLY DRAWING (Continued)
®
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SureTemp Model 670/SureTemp 4 Model 675
33
Welch Allyn, Inc.
FIGURE 5 - SYSTEM SCHEMATIC
34
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®
SureTemp Model 670/SureTemp 4 Model 675
Technical Manual
FIGURE 5 - SYSTEM SCHEMATIC (CONTINUED)
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SureTemp Model 670/SureTemp 4 Model 675
35
Welch Allyn, Inc.
NOTES: UNLESS OTHERWISE SPECIFIED
1
MAXIMUM LEAD PROTRUSION OF COMPONENT CONTACTS TO BE .030 INCH, AS SHOWN.
2
INSTALL SWITCH CONTACTS (PART OF S4 & S5) WITH LONG AXIS, AS SHOWN.
3
INSTALL CERAMIC RESONATOR (X1) WITH LETTERING FACING S4 & S5 END OF BOARD.
4
SOLDER CAPACITOR (C13) ACROSS TWO LEADS OF Q11, AS SHOWN.
5
INSERT POLARIZING KEY (DIATEK P/N 58514-0000) INTO CONNECTOR (J1) IN POSITION
SHOWN AND SECURE WITH LOCTITE ADHESIVE 495.
FIGURE 6 - MAIN PCA
36
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SureTemp Model 670/SureTemp 4 Model 675
Technical Manual
FRAME
DIATEK P/N 25092-000
2
3
4
LCD
DIATEK P/N 60011-000
ZEBRA CONNECTOR
DIATEK P/N 58112-000
1
LAMP
DIATEK P/N 58104-000
TRANFORMER
DIATEK P/N
52005-000
BOTTOM VIEW
DISPLAY PCA
DIATEK P/N 20926-000
2
NOTES: UNLESS OTHERWISE SPECIFIED
1
INSTALL INSULATION TAPE ALONG METAL SURFACE OF TRANSFORMER AS SHOWN.
2
CLEAN CONTACT AREA ON LCD AND PCA WITH ISOPROPYL ALCOHOL. THEN ALLOW
TO DRY BEFORE ASSEMBLY.
3
FINGER PROTECTION MUST BE WORN DURING ASSEMBLY OF ELASTOMERIC
CONNECTOR.
4
INSPECT ELASTOMERIC CONNECTOR FOR VISIBLE CONTAMINATION: IF
CONTAMINATED, DO NOT USE OR ATTEMPT TO CLEAN.
MAIN PCA
MODEL 670: DIATEK P/N 20905-000
MODEL 675: DIATEK P/N 20905-010
FIGURE 7 - ELECTRONICS ASSEMBLY
®
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SureTemp Model 670/SureTemp 4 Model 675
37
Welch Allyn, Inc.
THERMOMETER REASSEMBLY
Note: Most of the screws in the unit are plastic thread rolling screws and do not require excessive tightening
which will strip out the case plastic threads.
1.
If the electronics assembly has been removed from the mid-frame, solder the battery wires and the horn
wires to the main PCA, then slide the main PCA into the two retaining tabs near the center of the mid
frame and insert the top of the main PCA under the two plastic tabs towards the top of the mid-fame.
2.
Lay the front case face-down on a flat surface.
3.
Ensure that the display window has been cleaned and installed in the front case, with its slightly rough,
scratch resistant surface facing outward.
4.
Carefully slide the display board assembly under the retaining tabs at the top of the front case.
5.
Gently press the bottom of the display board until it contacts the screw wells in the front case and install
the two shortest display board retaining screws.
6.
Install 3 “AA” batteries according to the battery polarities marked inside the battery compartment. Verify
that the thermometer completes self-test, and the display goes blank.
CAUTION: Incorrect battery polarity may result in damage to the thermometer.
7.
Install the back case.
8.
Install the battery door.
9.
Insert all four screws into the back case, but leave loose. Note that there are two shorter screws for the
display area, and one machine screw for the Battery Door.
10. Insert one of the neck strap pins into its receptacle and tighten the screw adjacent to the receptacle.
11. Insert the other neck strap pin into its receptacle and tighten the screw adjacent to it.
12. Tighten the two remaining screws.
13. Install the °F-°C / NORMAL-MONITOR label (at the top of the thermometer).
14. Plug the probe into the thermometer.
15. Insert the probe into the probe storage channel. Verify that the thermometer displays “OrL” (briefly for
Model 670 and for several seconds for Model 675) then goes blank.
38
®
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SureTemp Model 670/SureTemp 4 Model 675
Technical Manual
SUGGESTED SPARE PARTS LIST
Welch Allyn Part No.
25088-001
25089-001
25090-100
25091-001
25092-000
25103-000
30056-0000
40301-0020
40301-2120
40301-3720
44043-0000
44046-0000
46128-4760
46129-1050
47017-000
50004-0000
50029-0000
50030-0000
50031-0000
50032-0000
52005-000
53009-000
54249-000
58096-000
58097-000
58100-000
58101-000
58102-000
58103-000
58104-000
58112-000
58411-000
58412-000
58413-000
58465-000
58514-0000
60011-000
70082-000
70082-001
80013-0002
80013-001
83021-0000
83035-000
83036-0000
83037-000
Description
Case Front
Case Back
Mid-Frame-drilled
Battery Door
Frame, Zebra
Window, Display
Pin, Strap
Resistor, 10.0K Surface Mount 0.1% 0805 Size
Resistor, 12.1K Surface Mount 0.1% 0805 Size
Resistor, 13.7K Surface Mount 0.1% 0805 Size
Diode, XX459, Low Leakage, Surface Mount, Mini Melf
Diode, XXX4448/XX459 Surface Mount, Mini Melf
Capacitor, 47µF Tant. Chip, 10V + 20% D Case
Capacitor, 1µF Tant. Chip, 16V + 20% D Case
Resonator, Ceramic 4.00MHz, with Caps
Transistor, PN2222
Transistor, XX2222A NPN, SOT-23
Transistor, XX5087, PNP, SOT-23
Transistor, BCX69 PNP, SOT-89
Transistor, BSS138, FET, SOT-23
Transformer, Subminiature, PC Leads .1W
Battery. Alkaline, “AA”
IC, Microprocessor
Spring, Contact -Gold Stripe AMP 62314-2
Contact, Bottom -Gold Stripe AMP 62313-4
Switch, Slide MA012-4-CE-P-RA
Switch, Probe
Horn, Piezo
Cable, Flexible, Ansley FSN-12A-30
Lamp, Electroluminescent
Connector, Zebra
Battery Contact, Common
Battery Contact, Positive
Battery Contact, Negative
Connector, 6 Conductor
Polarizing Key, Between Contact
LCD Display
Label, Serial Number
Blank Overlay, Serial Number Label
Wire, 26 AWG Stranded - Red
Wire, 26 AWG Stranded - Black
Screw, Thread roll #4 x 1/4 Philips
Screw, Thread roll #4 x 7/8 Plastilok
Screw, Machine 4-40 x 1 1/16 Philips
Screw, Thread roll #4 x 3/4 Plastilok
Qty Per 100 Units
5
2
10
2
15
4
2
1
1
1
2
2
2
2
2
4
1
1
1
2
2
30
2
4
4
4
4
4
4
10
10
4
2
2
6
6
10
2
2
2 feet
2 feet
4
2
2
4
OPTIONS AND ACCESSORIES
• Wall mount bracket with locking mechanism for securing thermometer to wall or cabinet.
• Calibration Key for verifying calibration - inserts in place of probe plug and provides correct reading of
97.3°F.
• Rectal Probe
• Thermometer Stand
• Second Probe Holder
• Calibration Tester (Model 9600)
®
®
SureTemp Model 670/SureTemp 4 Model 675
39
7420 Carroll Road, San Diego, California 92121 • (800) 854-2904 • (619) 621-6600 • FAX (619) 621-6610
70840-0000A