MODEL 370 pH/mV METER OPERATING MANUAL 370 350/REV A/10-03

MODEL 370 pH/mV METER OPERATING MANUAL 370 350/REV A/10-03
MODEL 370 pH/mV METER
OPERATING MANUAL
370 350/REV A/10-03
MODEL 370
pH/mV METER
OPERATING INSTRUCTIONS
CONTENTS
Introduction
Specification
Installation
Displays
Controls
Operation
Calibration
Error Codes
mV Mode
Manual Temperature Compensation
Auto Shut Off
Data Storage
Good Practice Guidelines
Maintenance
Troubleshooting Guide
Checking pH Electrode Function
Checking pH Meter Function
Checking Temperature Input
Battery Replacement
Optional Accessories
Spare Parts
EC Declaration of Conformity
1
1
2
2-3
4
5
5-7
8
8-9
9
9
10
11
12
13-14
14
15
15
16
16
16
17
MODEL 370
pH/mV METER
OPERATING INSTRUCTIONS
INTRODUCTION
The Model 370 is a general purpose hand held pH/mV meter
offering a 1 or 2 point calibration and automatic buffer recognition
with manual override. The custom liquid crystal display
simultaneously shows temperature compensated pH readings or
electrode potential and temperature. The instrument is housed in a
robust, ergonomically designed case. Calibration errors are clearly
indicated together with the parameter in error. An indication of
battery life is also permanently shown on the display. An
automatic switch off facility helps to conserve battery life.
SPECIFICATION
pH
Range:
Resolution/Accuracy:
mV
Range:
Resolution/Accuracy:
Temperature Ranges:
Resolution/Accuracy:
ATC Range:
Manual Temp. Comp. Range:
Auto Buffer Recognition:
Calibration:
Power:
Battery Life:
Size:
Weight:
(1 or 2 point cal)
-2 to 16.00pH
0.01pH / ±0.02pH
(Absolute or Relative)
-1999 to +1999mV
1mV / ±1mV
-10 to +105°C / 14 to 221°F
0.1°C / ±0.5°C / 1°F / ±1°F
0 to 100°C / 32 to 212°F
0 to 100°C / 32 to 212°F
4.00, 7.00, 9.22, 10.00
(manual override)
User selectable 1or 2 pt
2 AA cells
500 hours typical
(@ 25°C with alkaline cells)
175(l)x75(w)x35(d)mm
250g
1
INSTALLATION
Unpack the instrument and ensure the following items are present:
1. Model 370 pH/mV Meter (370 201)
2. Epoxy bodied combination pH electrode (924 001)
3. Temperature/ATC probe (027 500)
4. pH4, 7 & 10 buffer sachets
5. 2 x AA alkaline batteries (021 007)(fitted)
Optional accessories which may have been ordered:
1. Carrying Case (033 268)
DISPLAYS
1.
Main display - 3½ digit display providing direct readout of
pH or mV. Underrange (-1) and Overrange (1) symbols will
be displayed if the instrument is reading outside the
ranges of:
pH -2.00 to 16.00
or mV -1999 to +1999
In addition, the instrument will display an erroneous
result momentarily at the same time as the secondary
display indicates the error code.
2
2.
Secondary display - 4 digit display showing
temperature (manual temperature compensation value or
ATC probe temperature, if connected) in °C or °F. In the
event of a calibration error the display will show an
error code momentarily (if the reading is outside the
range of -10 to 105°C / 14 to 220°F) at the same time as
the primary display indicates the erroneous reading.
These codes will be shown as Err1, Err2 or Err3.
3.
CAL 1 or CAL 2 indicator - shows which point of the
calibration routine has been reached.
4.
Battery Life Indication - 4 levels will be shown ranging
from <25%, 25-50%, 50-75% and 75-100%. Sensor
calibration data and user parameters are retained during
battery replacement.
5.
Mode annunciator - pH or mV is displayed depending on
which mode of operation is selected.
6.
REL - this is the relative mV mode annunciator. The
relative mV mode is selected via the Cal key. If the mV
mode is selected and this annunciator is not shown then
the instrument is reading in absolute mV.
7.
MAN - this is displayed to indicate when manual
temperature compensation or manual pH calibration is
being performed. This will not appear on the display
when the ATC probe is connected.
8.
RCL annunciator - this indicates that the displayed
reading is the stored value recalled from memory.
3
KEYPAD CONTROLS
STO RCL
STO stores the current data reading.
RCL enters recall mode to view the stored
readings.
I:O
Switches the instrument on and off. This key
should be pressed and held for 1-2 seconds to
operate. The instrument will automatically switch
off after 30 minutes if no key is pressed.
Back light. Pressing this key will illuminate the
back light for 10 seconds. It should be noted
that, if used excessively, this will reduce battery
life.
56
Enables manual setting of pH buffer values when
performing a calibration, and adjustment of the
manual temperature compensation value (no ATC
probe connected).
CAL
This key is used to select and perform
calibration in the pH mode. In the mV mode
pressing the Cal key will toggle between Absolute
and Relative mV.
MODE
This key changes the measurement parameter
to pH or mV mode as required and sets to °C/°F.
Press and hold for 3 seconds to select temperature
unit.
4
OPERATION
Switch the instrument on by holding down the I/O key for 1-2
seconds. All display segments will be illuminated for approximately
2 seconds. The display will either power up in the mV or pH mode
depending upon previous usage. An internal self check routine is
run during this display and on successful completion normal
operating mode is activated.
If no ATC probe is connected to the instrument the MAN
annunciator will be shown. Manual temperature compensation
should always be entered prior to commencing a calibration.
Remove the electrode from the packaging and ensure it is in good
condition. Connect the electrode to the instrument via the BNC
socket and remove the wetting cap. Prior to performing pH
measurement it is necessary to perform a 1 or 2 point calibration
using the buffer sachet(s) provided. Connect the ATC probe (if
being used) to the mini-DIN socket and immerse the ATC probe in
the pH buffer alongside the pH probe.
CALIBRATION
The 370 features a one or two point calibration. For the best
results we recommend that the 370 is calibrated with buffer
solutions that are close to the sample value, where possible. For
example: when working at pH5.5 we recommend calibrating at
pH7 and pH4.
Auto buffer recognition operates over the range of 0 to 100°C,
and will recognise 4.00, 7.00, 9.22 and 10.00pH. Alternative
manual values may be entered during the calibration sequence by
using the56 keys to set the preferred values.
NOTE: Manual temperature compensation (if being used) should
be entered prior to commencing a calibration sequence using the
56 keys. (If the displayed reading is altered the auto buffer
5
recognition feature will be disabled. To retrieve the auto buffer
recognition values it is necessary to exit the calibration sequence
by pressing the MODE key).
To exit the cal sequence at any point, press the MODE key.
Rinse electrode(s) in deionised water between
measurements.
Select pH using the MODE key. To commence the calibration
immerse the tip of the electrode and the ATC probe into the first
buffer solution so that the bulb and reference junction are
covered.
AUTOMATIC CALIBRATION FIRST POINT
Press the CAL key and the display will show the CAL1
annunciator. The primary display will show a reading close to the
buffer value based on the last successful calibration.
For automatic calibration to one of the pre-programmed buffer
values wait for the reading to stabilise and then press the CAL
key again to update the display to the temperature corrected value
for the buffer used (refer to the buffer value tables on buffers
used).
If a one point only calibration is required, pressing the MODE key
will return the display to the pH measurement mode. The
instrument is then ready to perform sample measurements.
AUTOMATIC CALIBRATION SECOND POINT
If a two point calibration is required the electrode should be rinsed
and then immersed in the second buffer solution.
6
The primary display will show a reading close to the buffer value
based on the last successful calibration. For automatic calibration
to one of the pre-programmed buffer values wait for the reading
to stabilise and then press the CAL key again to update the display
to the temperature corrected value for the buffer used (refer to
the buffer value tables on buffers used).
MANUAL CALIBRATION FIRST POINT
Press the CAL key and the display will show the CAL1
annunciator. The primary display will show a reading close to the
buffer value based on the last successful calibration.
For manual calibration press the 56keys to change the reading
to the value for the specific buffer being used. When the correct
value is achieved press the CAL key again to confirm this value.
MANUAL CALIBRATION SECOND POINT
If a two point calibration is required the electrode should be rinsed
and then immersed in the second buffer solution.
For manual calibration press the 56 keys to change the reading
to the value for the specific buffer being used. When the correct
value is achieved press the CAL key again to confirm this value.
CALIBRATION COMPLETE
For both automatic and manual calibration procedures the last
(3rd) press of the CAL key returns the display to the pH
measurement mode and sample measurement can proceed.
7
ERROR CODES
Refer to Troubleshooting Guide for possible causes of error
codes. If a problem is detected during calibration the following
error codes will be displayed:
Err1 This indicates that the calculated electrode offset at pH7 is
outside the range of -30 to +30mV. The error code will be
displayed for 3 seconds on the secondary display, together with
the erroneous electrode offset value in mV on the primary display.
The instrument will then reset the calibration data back to the ideal
Nernst response of 0mV offset at 7pH and a slope of 59.16mV/pH
at 25°C.
Err2 This indicates that the slope value is out of range. The
error code will be displayed for 3 seconds on the secondary
display, together with the erroneous value as a % on the primary
display. The instrument will then reset the calibration data back to
the ideal Nernst response of 0mV offset at 7pH and a slope of
59.16mV/pH at 25°C. The allowable range for slope is 75 to 125%
of the ideal Nernst figure.
Err3 This indicates that the instrument has not recognised the
buffer. The displayed reading must be within 1pH of the calibration
buffer value for automatic buffer recognition. The error code will
be displayed for 3 seconds on the secondary display, together
with the erroneous pH buffer value on the primary display. The
instrument will then reset the calibration data back to the ideal
Nernst response of 0mV offset at 7pH and a slope of 59.16mV/pH
at 25°C.
mV MODE - Absolute mV
When this mode is selected the instrument will display the actual
voltage developed by the electrode when it is immersed in a
solution containing ions to which the electrode is sensitive.
Combination type pH, redox and ion selective electrodes can all be
used in this mode. Most of these determinations will require the
preparation of calibration curves or other analytical methods for
the results to be converted to a concentration unit.
8
This range is also useful for monitoring the performance of
standard pH electrodes. Using accurate and fresh buffers at a
constant temperature the mV output of the electrode should be
noted and compared to the theoretical ideal.
As the electrode ages, becomes contaminated or dirty, these
values will drift, indicating that corrective action should be taken.
Recording these values as part of a routine quality control
programme can give a good indication of the condition of the
electrode.
Relative mV
This mode is also suitable for determinations using redox and ion
selective electrodes with the additional benefit of being able to
zero any offset developed by the electrode in a blank solution, i.e.
a solution that has none of the ions to be measured, but has all the
other characteristics of the unknown samples. A blank solution
would normally have its ionic strength and pH adjusted as required
for the electrode in use.
As the display is zeroed automatically when the relative mV mode
is selected, it is necessary to immerse the electrode in the blank
solution with the absolute mV mode selected. When the reading
has stabilised the relative mV mode should then be selected by
pressing the CAL key. The display will be set to zero, thereby
removing any offset voltage. Sample measurement is then carried
out by using a variety of well tried analytical methods; from simple
calibration curves through titrations, to single and multiple addition
methods.
MANUAL TEMPERATURE COMPENSATION
When making measurements without ATC, the displayed
temperature reading can be adjusted to the correct value using the
56 keys. The instrument will default to this mode if a
temperature sensing element is not detected by the electronics.
Manual temperature adjustment must be made prior to commencing
a calibration sequence or sample measurement.
AUTO SHUT OFF
This will occur after 30 minutes if no key is pressed
9
DATA STORAGE
The 370 can store up to 32 readings. Storage is intiated by manual
key press.
Storing Data
Pressing the STO key stores the current reading in the next
available data location. The storage location is indicated by Sto
and a number (1-32) momentarily displayed for the data. The
results are stored sequentially until the memory is full. When all 32
data locations are filled, the next stored reading will overwrite the
result previously stored in position 1. The stored data is retained in
the event of battery failure and during battery replacement.
Recalling Data
Pressing the RCL key recalls the last stored reading on to the
display. The instrument is now in RCL mode, indicated by the RCL
annunciator at the top of the display.
The 56 keys are used to select previously stored data. The
storage location is indicated by rCL and a number (1-32)
momentarily displayed prior to the data.
To clear all readings press and hold the CAL key (>3 seconds)
while in RCL mode. When all stored readings are cleared the
display will momentarily show CLr ALL. The instrument will then
return to the main operating mode.
If storage locations are empty and the RCL key is pressed, the
display will show ALL CLr.
NOTE: It is not possible to delete individual stored
readings.
10
GOOD PRACTICE GUIDELINES
The types of pH electrodes are many and various. The supplied
epoxy combination electrode is suitable for the majority of tests
carried out on aqueous solutions.
For other applications, such as low ionic strength, high
temperatures and strongly acidic solutions a more suitable pH/
reference electrode pair may be required. Details or advice
supplied on request.
The following general guidelines indicate the care and
maintenance required:
1. After Use - Rinse thoroughly with distilled water.
Short Term Storage - Immerse in storage solution (025 192)
Long Term Storage - Fit wetting cap filled with storage solution
(025 192) and replace in original packaging.
2. Electrodes should be stored:
a) away from direct sunlight
b) in a vertical position
c) within their specified temperature range
3. Always ensure the electrode is used within its specified
temperature range. Ageing of electrodes used above their
specified temperature is rapid and irreversible.
4. DO NOT touch the sensitive glass pH membrane or reference
junction. Excess droplets of solution may be removed by gently
blotting with filter paper or tissue.
DO NOT rub the electrode as this may induce an electrostatic
charge.
5. During use ensure the electrode is rinsed between each
measurement to eliminate the contamination of solutions.
11
MAINTENANCE
CLEANING/RE-CONDITIONING OF GLASS ELECTRODES
For general purpose use, combination electrodes can be cleaned
with a mild detergent solution or a commercial glass cleaning
solution (provided these are not strongly acidic). The electrode
surface should be wiped with a clean cloth soaked in the cleaning
agent, and/or allow the membrane to stand in the solution until
clean. Rinse and repeat as necessary.
TABLE FOR CLEANING OF GLASS ELECTRODES
NOTE: The epoxy bodied electrode supplied with the
instrument should not be cleaned with aggressive
solvents.
Deposit
General deposits
Inorganic coatings
Metal compounds
Oil/Grease
Resins/Lignins
Proteins (blood, etc)
Stubborn deposits
Cleaning agents
Mild detergent solution
Commercial glass cleaning solution
(not strongly acidic)
Acid solution, not stronger than 1M
Complexing agent (EDTA) or suitable
solvent
Acetone, alcohol or detergent (not
strongly alkaline)
Enzyme solutions e.g. Pepsin in 0.1M
HCl
Weak hydrogen peroxide solution,
Sodium Hypochlorite solution or
domestic bleach.
Electrodes which have been allowed to dry out, (often indicated
by a hard, dry deposit of KCl crystals on the electrode body),
should be rehabilitated by soaking overnight in warm deionised
water.
12
TROUBLESHOOTING GUIDE
FAULT
PROBABLE CAUSE
ACTION
No power
Battery failure
Battery polarity incorrect
Replace batteries
Refit batteries
Cal error
1, 2 or 3
Incorrect value buffer used Use correct value
Contaminated buffer solution Use fresh buffer
solutions
Cal error
1 or 2
pH electrode defective
Replace pH electrode
Same buffer used for 2 point Recalibrate on 2
buffer solutions
cal
Unstable
display
pH electrode defective
Display
shows 1 or
-1 only
Intermittant or no connection Check electrode
connection to unit
pH electrode defective
Replace pH electrode
Contaminated solutions
Replace solutions
Replace pH electrode
Temp. value Defective temperature probe Replace temperature
probe
incorrect
Intermittant
display
Probes not fitted correctly
Check connections
I:O key not held down >2
I:O switch
not working secs
No batteries fitted
Retry holding key for 2
seconds
Fit batteries
56 keys Operating in incorrect mode
not working
Refer to operation
section of manual
13
TROUBLESHOOTING GUIDE
FAULT
PROBABLE CAUSE
ACTION
Back light not
on/goes out
10 second time
elapsed/normal
function
Recheck
Unable to
adjust manual
temperature
Incorrect mode of
operation
ATC probe connected
Reselect mode
MAN displayed
when ATC
probe
connected
Defective ATC probe
Replace ATC probe
Disconnect probe
If a fault is identified during the start up self check routine an error
code will be displayed. This indicates an internal hardware or
software software problem. In the event of this, please contact
your local distributor or service agent.
CHECKING pH ELECTRODE FUNCTION
If the pH electrode is considered to be defective the following
procedure can be carried out to confirm this:
Select the mV mode and place the electrode in a fresh 7pH buffer
solution. Record the mV value as Eo which should be between -30
and +30mV.
Rinse the electrode and place in a fresh 4pH buffer solution.
Record the mV value as ‘k’ which should be between +133 + Eo and
+222+Eo.
14
The slope of the electrode can be calculated from:
Slope % = k + Eo x 100
177.48
This value should be in the range of 75% to 125%.
If any of the parameters are outside the limits given the electrode is
faulty and should be replaced.
CHECKING pH METER FUNCTION
Remove the ATC probe and set the temperature display to 25°C to
enable manual temperature compensation at this temperature.
Connect the meter to a mV source and apply 0mV. Press the CAL
key and the display should read 7 pH.
Apply +180mV and calibrate to 4 pH.
Apply -180mV and the display should show 10 pH.
If the above can be completed successfully the meter can be regarded as operating correctly and the electrode as suspect. This
can be confirmed by re-calibration with a replacement or known
good electrode.
CHECKING TEMPERATURE INPUT
Apply a 10.0Kohm resistor across the pins shown:
Check the display reads 25.0°C ±0.5°C
15
BATTERY REPLACEMENT
If necessary, switch the unit off using the I/O key.
To fit new batteries; loosen the battery compartment cover (the
screws are captive in the cover), remove and carefully discard
the used batteries. Fit the new batteries, type R6, AA or AM3,
ensuring the correct polarities are observed, as indicated on the
moulding. Refit the battery compartment cover, ensuring that the
fixings are secured into place, but are not overtightened.
OPTIONAL ACCESSORIES
The following list of items are available for use with the Model 370:
033 268
025 179
025 180
025 181
Carrying Case
pH 4 buffer sachets (pack 10)
pH 7 buffer sachets (pack 10)
pH 10 buffer sachets (pack 10)
Comprehensive ranges of electrodes and consumables are
available for use with this product. Details available on
www.jenway.com
SPARE PARTS
Epoxy bodied pH electrode
ATC probe
Battery (Qty 1) (2 equired)
924 001
027 500
021 007
Recommended spares list for 2 years:
Batteries (Qty 8)
021 007
Epoxy bodied pH electrode (Qty 2)
924 001
ATC probe (Qty 1)
027 500
16
EC Declaration of Conformity
JENWAY Model 370 pH/mV Meter complies with the following
European Standards:
EN 50081-1:1992
Electromagnetic compatibility - Generic
emission standard
EN 61326:1998
Electrical equipment for measurement,
control and laboratory use - EMC
requirements
EN 61010-1:1993
Safety requirements for electrical
equipment for measurement, control and
laboratory use
Following the provision of:
EMC Directive - 89/336/EEC and Low Voltage Directive - 73/23/EEC
17
Thank you for reading this data sheet.
For pricing or for further information, please contact us at our UK Office, using the details
below.
UK Office
Keison Products,
P.O. Box 2124, Chelmsford, Essex, CM1 3UP, England.
Tel: +44 (0)1245 600560
Fax: +44 (0)1245 600030
Email: [email protected]
Please note - Product designs and specifications are subject to change without notice. The user is responsible for determining the
suitability of this product.
Thank you for reading this data sheet.
For pricing or for further information, please contact us at our UK Office, using the details
below.
UK Office
Keison Products,
P.O. Box 2124, Chelmsford, Essex, CM1 3UP, England.
Tel: +44 (0)1245 600560
Fax: +44 (0)1245 808399
Email: [email protected]
Please note - Product designs and specifications are subject to change without notice. The user is responsible for determining the
suitability of this product.
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