HP | 3400B | User manual | HP 3400B User manual

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The HP 34008 is a true root-means-square (RMS) analog voltmeter
capable of measuring ac voltages from 100 microvolts to 300 volts.
It is extremely flexible for audio and RF measurements from 10 Hz to
20 MHz and allows you to measure broadband noise and fast
rise-time pulses.
s Full-scale measurements of non-sinusoidal waveforms with crest
factors (the ratio of peak voltage to RMS voltage) up to 10:1 can be
made. At 1/10th of full scale, pulse trains with 0.01% duty cycle
(100:1 crest factor) can be measured accurately.
е A single front-panel control selects one of 12 voltage ranges (1 mV to
300 V) or decibel ranges (72 dBm to +52 dBm),
e À dc output is provided on the rear panel which is proportional to the
front-panel meter reading. By using this voltage to drive auxillary
equipment, you can use the voltmeter as an RMS ac-to-de converter.
se Suitable for bench use or can be rack-mounted using the available
combining case or adapter frame accessories.
The HP 3400B is a form, fit, and function replacement for the original
HP 3400A. Completely redesigned, the “B” version extends the
bandwidth from 10 MHz, available with the “A” version, to 20 MHz.
The HP 3400B User and Service Guide contains new specifications and
calibration procedures for the improved performance of the HP 3400B.
Updated schematics and replaceable parts lists are also included.
HP 3400B
RMS Voltmeter
The Front Panel at a (zlance
DECIBELS бо : D
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“8 PACKARD RMS VOLTMETER
dB Power
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1 Direct reading meter (RMS volts and dB) 3 Input BNC connector
2 Zero adjustment screw 4 Range selector switch (volis and dB)
The Rear Panel at a Glance
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1 Powerline fuse-holder assembly 3 DC output jack. Provides -—1 Vdc output
# Power-line voltage setting at full-scale defiection; output is proportional
to deflection; source impedance is 1 kL
Specifications
Voltage Ranges:
dB Range:
Frequency Range:
Response:
Messuremant
Accuracy:
20°C io 30°C
(1 Year)
AC-1o-DC Converter
Aceuracy:
30°C to 30°C
1 maV,3mV, 10 mV, 30 mV, 160 mV, 300 mV,
1V,3V,10V,30V, 100 V, 300 Y full scale.
—~72 dBm to +52 dBm
(0 dBm= 1 mw into 6000).
10 Hz to 20 MHz
Responas to RMS valus (heating value) of input.
From 1/10th scale to full scale is % of ful scale,
Temperature cosfficiant: + 0.10% per “C from
OC to 20°C and 30°C to 55°C.
Frequency + % of Full Scale
10 Hz to 50 Hz + 5%
50 Hzto 1 MHZ + 1%
1 MHZ to 2 MHz + 2%
2 MHZ to 3 MHz + 3%
3 MHz to 20 MHz + 5%
Note: The voltmeter may show a Zero offset with
no voltage applied to the Input terminal.
Temperature coefficient: + 0.10% per "C from
C'C to 20"C and 30'C to 55°C,
Frequency + % of Full Scale
10 +17 10 50 Hz + 5%
50 Hz 10 1 Miz + 0.75%
1 MHZ to 2 MHZ + 2%
2 MHz to 3 MHz + 3%
3 MHZ to 20 MHz +5%
Note: The volimeter may show a zero offset with
no voltage applied to the input terminal.
input impedance:
Стее! Factor:
AC Overload:
Max. Continuous
Input Voltage:
Max. DC Input:
Response Time:
DC Output:
Output Noise:
Power:
Weight:
Size:
Storage Temperature:
1 mV 10 300 mV ranges: 10 MO) shunted
by < 50 pF. AC-coupled input. -
1 Y 10 300 Y ranges: 10 MO shunted
by < 20 DF. AC-coupled Input.
{Ratio of poaicto-RMS amplitude of Input.)
10:1 at full scale except where limited by
maximum input, and inversely proportional
10 meter defiectión (6.9, 70:1 ai halí-scaie,
100:1 at tentitscele).
30 dB above full scale or 800 Vpaak,
whichever is less, on each range.
500 Vac peak at 1 kHz or 600 Vdc on
alt ranges.
500 Y on any renge.
For a step function, < 5 seconds to
respond to final value.
Negative 1 Vde into open circuit for full scale
defisction, proportional to meter defiection,
| MA max; nominal source Impedance + id.
< 1 my AMS
+00 Y / 120 Y / 220 Y / 240 Y + 10%.
48 Hz lo 440 Hz, 10 Walls,
2.2 Kg (4.2 los); shipping: 4.0 kg (8.7 Ibs).
16.5 cm (H) Xx 13.0 cm (W) x 28.7 ст (D)
=10°C to +60°C
©) uick Start
One of the first things you will want to do with your voltmeter is to
become acquainted with its front panel. We have written the exercises
in this chapter to prepare the voltmeter for use and help you get
familiar with some of its front-panel operations.
10
Chapter 1 Quick Start
To prepare the voltmeter for use
Caution
To prepare the voltmeter for use
The following steps help you verify that the voltmeter is ready for use.
Check the list of supplied items.
Verify that you have received the following items with your voltmeter.
If anything is missing, contact your nearest Hewlett-Packard Sales Office.
[7 One double binding post to BNC adapter.
L] One power cord.
LJ One 125 mA power-line fuse is installed.
Y This User and Service Guide.
Verify the power-line voltage setting.
Four line voltage settings are available: 700, 120, 220, or 240 Vac.
The line voltage was preset at the factory to the proper value for your
location. Change the voltage setting if it is not correct (see page 12).
A 125 mA fuse is installed when the voltmeter is shipped from the
factory. This is the correct power-line fuse for 100, 120, 220, or 240 Vac
operation.
Connect the power cord and turn on the voltmeter.
The front-panel Power indicator will light up when you turn on the
voltmeter. Allow five minuies for the voltmeter to warm up and stabilize
before making measurements.
Do not measure signals greater than 80 volts with 10 io 1 crest factor,
otherwise, the maximum input rating of 800 volts peak will be exceeded,
When measuring signals up to 80 volts with a 10 to 1 crest factor, use the
double binding post to BNC adapter (or equivalent) supplied with the
volimeter.
11
Chapter 1 Quick Start
To prepare the volimeter for use
1 Remove the fuse-holder assembly from
the rear panel,
2 Remove the line-voltage selector from
the assembly.
3 Rotate the hne-voltage selector until the
correct voltage appears in the window.
4 Replace the fuse-holder assembly in
the rear panel.
100, 120, 220 or 240 Vac
Verify that the correct line voltage appears in the window.
12
1
1
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atar нии
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Chapter 1 Quick Start
To select the range
To select the range
You can make measurements using one of 12 voltage ranges available.
The voltmeter is capable of measuring true-RMS ac voltages from
100 uV to 300 V.
Caution
When measuring an ac signal superimposed on a de level, you should
always set the range selector switch to the 300 volt position. A high- Lo an _
voltage transient caused by the application of a de voltage will damage
¡he volimeter $ три circuliry.
Select the 300 Y range first
and then adjust the range
until the meter reads in the
upper two-thirds of the scale.
DECIBELS
t my enol)
ALE Ewes
14008
RS VOLTMETER
Vols — de Power
=
Zero Adjustment — |
Screw
12 ranges available
Note The voltmeter may show a zero offset with no voltage applied io
the input terminal,
Note If the meter pointer does not indicate “0” when the voltmeter has
been turned off for at least one minute, you should adjust the zero screw
setting. See chapter 2, “Calibration Procedures,” for more information.
13
Chapter 1 Quick Start
To use the DC output signal
To use the DC output signal
You can create plots of measured data and make higher resolution
measurements by connecting an X-Y plotter or digital multimeter to the
rear-panel DC output jack. On the I's ranges (0.001, 0.01, 0.1, 1, etc),
the voltage measured at the jack is normalized to ~1 Vdc and is
proportional to the RMS input voltage (-1 Vde corresponds to a
full-scale meter deflection). On the 8's ranges (0.003, 0.03, 0.3, 3, etc),
the full-scale output is -0.9487 Vdc.
A phone plug for the DC output jack is available by ordering
HP part number 1251-0067.
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1 mA max; hominal source impedance 1 kQ.
Negative 1 Vdc into open circuit for full scale deflection;
proportional to meter deflection.
ни
|
Chapter 1 Quick Start
To rack mount the voltmeter
To rack mount the voltmeter
You can mount the voltmeter in a standard 19-inch rack cabinet using
one of two optional kits available. If your application requires that you
frequently remove the voltmeter from the cabinet, the combining case 1s
recommended. You can also use the combining case on the bench to
mount the voltmeter with other HP System I instruments. The rack
adapter frame is recommended for permanent or semi-permanent rack
mounting applications.
Remove the front and rear feet before mounting the voltmeter in the
combining case or rack adapter frame.
To remove the feet, press down on the release tab and slide to side.
15
Chapter 1 Quick Start
To rack mount the voltmeter
x
To use the combining case, order part number HP 1052A and rack
mount kit 5080-8
om
<
To use the rack adapter frame, order part number HP 5060-8762.
16
Calibration
Procedures
Warning
Caution
Calibration Procedures
This chapter contains procedures for performing the voltmeter s
verification and adjustment procedures. Notice that the verification
procedures are divided into two levels: Operation Verification (verifies
that the voltmeter meets selected testable specifications) and
Performance Verification (verifies that the voltmeter meet all testable
specifications). The chapter is divided into the following sections:
es Calibration Interval 19
Time Required for Calibration 19
e Recommended Test Equipment 20
e Test Considerations 20
e Operation Verification Procedures 21
e Performance Verification Procedures 22
e Adjustment Procedures 28
e Test Connector Pinout 36
The verification tests use the voltmeter s specifications listed in
“Specifications” on page 4.
The information in this chapter is for service-trained personnel who are
familiar with electronic circuitry and are aware of the hazards involved.
To avoid personal injury or damage to the instrument, do not perform
procedures in this chapter or do any servicing unless you are qualified
io do so.
Some procedures in this chapter must be performed with power applied
to the voltmeter while the protective covers are removed. Energy
available at many points may, if contacted, result in personal injury.
Static electricity is a major cause of component failure. To prevent
damage to the electrical components in the voltmeter, observe anti-static
techniques whenever working on the volimeter.
18
Chapter 2 Calibration Procedures
Calibration Interval
Calibration Interval
The voltmeter should be calibrated on a regular interval determined by
the measurement accuracy requirements of your application. A 90-day
interval is recommended for the most demanding applications, while a
l-year or 2-year interval may be adequate for less demanding
applications. Hewlett-Packard does not recommend extending
calibration intervals beyond 2 years for any application.
Whatever calibration interval you select, Hewlett-Packard recommends
that complete re-adjustment should always be performed at the
calibration interval. This will increase your confidence that the
HP 3400B will remain within specification for the next calibration
interval. This criteria for re-adjustment provides the best measure of
the voltmeter s long-term stability. Performance data measured using
this method can easily be used to extend future calibration intervals.
When your voltmeter is due for calibration, contact your local
Hewlett-Packard Service Center for a low-cost recalibration.
Calibrations to MIL-STD-45662 are also available at competitive prices.
Time Required for Calibration
The Operation Verification, Performance Verification, and Adjustment
procedures in this chapter show you how to manually calibrate the
voltmeter. A complete verification and adjustment using these
procedures will take approximately one hour.
19
Chapter 2 Calibration Procedures
ommended Test Equipment
Recommended Test Equipment
The test equipment recommended for the verification and adjustment
procedures is listed below. If the exact instrument is not available,
select an equivalent substitute.
Application
Recommended Equipment
Range/Frequency Response Check (page 23, 24)
Amplifier Stability Check (page 25)
Overicad Protection Circuitry Check {page 26)
Crest Factor Check {page 27)
Front-Panel Meter Zero Adjustment (page 28)
Fuli Scale Gain Adjustment (page 29)
Tenth Scale Gain Adjustment (page 30)
Full Scale Pointer Adjustment (page 32)
20 MHz Flatness Adjustment (page 33)
Input Attenuator Adiustment (page 34)
Fiuke 5700A Calibrator, HP 34584 Multimeter
HP 8161A Puise Generator, HP 3458A Multimeter
Fiuke 5700A Calibrator, HP 34584 Multimeter
HP 8161A Pulse Generator, HP 3458A Multimeter
None
Fluke 5700A Calibrator, HP 3458A Multimeter
Fluke 5700A Calibrator, HP 3458A Multimeter
None
Fluke 5700A Calibrator, HP 3458A Multimeter
Fluke 5700A Calibrator, HP 3458A Multimeter
Test Considerations
To ensure proper instrument operation, verify that you have selected
the correct power line voltage prior to attempting any test procedure in
this chapter. See chapter 1, “Quick Start,” for more information.
¢ Assure that the calibration ambient temperature is stable and
between 18°C and 28°C.
e Assure that the ambient relative humidity is less than 80%.
e Allow the voltmeter to warm up for 30 minutes, with the covers in
place, before attempting any performance checks.
20
Chapter 2 Calibration Procedures
Operation Verification Proced
Operation Verification Procedures
The procedures in this section are used to provide a high level of
confidence that the voltmeter is meeting published specifications.
The Operation Verification test is a subset of the Performance
Verification tests and is suitable for checkout after performing repair.
The Operation Verification test is performed by completing a partial
range/frequency response test as described later in the Performance
Verification test procedures. This test verifies the voltmeter's frequency
response on the 1 volt range at full scale input levels, The signal
measured for this test is a de voltage taken at the rear-panel de output
jack. This voltage is normalized to -1 Vdc and is proportional to the
RMS input voltage (-1 Vdc corresponds to a full-scale meter deflection).
HP 34008 Calibrator Calibrator DC Output
Range Output Voltage Output Frequency (DMM Reading)
iv 1V 10 Hz -1.05 Y to -0985V
iV 1V 50 Hz -1.0075 V to =0.9926V
1V 1V 1 MHz ~1.0075V to -08826V
1V ТУ 2 MHZ -1.02 Y to —0.08 Y
1V iV 3 MHZ =1.03 Y to -0.87 V
1V iV 20 MHz -1.08V to -0.85 У
1 HP 34008: Select the 1 volt range.
2 Calibrator: Select a 1 volt ac signal at 10 Hz (use the “Wideband”
output on the Fluke 57004).
3 External Multimeter: Select the 10 Vdc range with bl, digits of
resolution.
4 Verify that the dc voltage measured at the rear-panel de output
jack is within the limits shown in the table above.
5 Continue checking the dc output as you adjust the calibrator’s
output voltage and frequency to each of the remaining values
shown in the table above.
21
Chapter 2 Calibration Procedures
Performance Verification Procedures
Performance Verification Procedures
The procedures in this section are used to test the voltmeter s electrical
performance using the specifications given on page 4 as the
performance standard. You can use these tests for incoming inspection,
periodic maintenance, and specification checks after a repair.
Note Allow the volimeter to warm up for 30 minutes, with the covers
in place, before attempting any performance checks.
Range/Frequency Response Check
This test verifies the voltmeter s frequency response on all 12 input
voltage ranges. The test is performed both at full scale and tenth scale
input levels. The signal measured for this test is a de voltage taken
at the rear-panel de output jack. On the 1's ranges (0.001, 0.01,
0.1, 1, etc), this voltage is normalized to ~1 Vdc and is proportional to
the RMS input voltage (—1 Vdc corresponds to a full-scale meter
deflection). On the 3's ranges (0.003, 0.03, 0.3, 3, etc.), the full scale
output is -0,9487 Vdc,
22
Full Scales Test
Chapter 2 Calibration Procedures
Performance Verification Procedures
1 HP 34008: Select the 0.001 volt range.
2 Calibrator: Select a 0.001 volt ac signal at 10 Hz,
3 External Multimeter: Select the 10 Vdc range with 51 digits of
resolution.
4 Verify that the de voltage measured at the rear-panel de output
jack is within the limits shown in the table below.
5 Continue checking the de output as you adjust the calibrator’s
output voltage and frequency to each of the remaining values
shown in the table below,
HP 34008 Calibrator Calibrator DC Output
Range Output Voltage Output Frequency (DMM Reading)
0.001 V 0.001 V 10 Hz -1.05V to 0.95 V
0.003 V 0.008 V 1 kHz 09558 V to 0,9416 V
0.01 Y 0.01 Y 1 kHz -1.0075V to -0.9925V
0.03 V 0.03 Y 1 kHz 0.9558 V to ~0.9416 V
9.1 \ 0.1 Y 1 kHz =1.0075 Y to -0.9925V
03V 0.3 Y 1 kHz 0.9558 V 10 -0,9416 V
iV 1V 10 Hz 1.05 V to -0,95 V
Ту 1V 50 Hz -1.0075 Y to -0.9925 V
ТУ 1V j kHz =1,0075 Y to -0.9925 Y
ТУ 1V 10 kHz 1.0075 V to -0.9925 V
ТУ 1V 100 kHz ~1.0075V to -0.9925 V
tv 1V 1 MHz =1.0075 V to -0.3925 Y
iV 1V 2 MHz 1.02 V to -0,98 V
iV 1V 3 MHz «103V to 097 V
tv 1iV 10 MHz «1.05 V to 0.95 V
1V 1V 20 MHZ «1,05 V to -0.95V
3V *3V 1 kHz 0.9558 V to -0.9416 Y
10 V *10 V 1 kHz +1.0075 V to -0.9925V
30 V *30 V 1 kHz ~0.9558 V to -0,9416 V
100 V *100 Y 1 kHz -1.0075 V to -0.9925V
300 V *300 Y 1 kHz ~0.9558V to 0.9416 V
* For all outputs less than 3 volts, use the "Wideband” output on the Fluke 5700A,
For outpuls greater than 3 voits, use the low frequency output,
23
Tenth Scale Test
Chapter 2 Calibration Procedures
Performance Verification Proced
1
HP 34008: Select the 1 volt range.
Calibrator: Select a 0.1 volt ac signal at 10 Hz.
External Multimeter: Select the 10 Vdc range with 5% digits of
resolution.
Verify that the de voltage measured at the rear-panel de output
jack 1s within the limits shown in the table below.
Continue checking the de output as you adjust the calibrators
output voltage and frequency to each of the remaining values
shown in the table below.
HP 3400B Calibrator Calibrator DC Output
Hangs Output Voltage Outpui Frequency {DMM Reading)
ТУ 9.1 \ 10 Hz 0.15 V to —0.05 V
iV 0.1 Y 50 Hz -1,075 Y to -0.0925 Y
1V 0.1 V 1 MHZ =-1.075 V to -0.0925 V
1V 0.1 V 2 MHz -0.12 V to 0.08 У
iV 0.1 V 3 MHz 0.13 V to 0.07 Y
ТУ 0.1 \ 10 MHZ 0.15 V to -0.05 Y
iV 0.1 Y 20 MHz {15 V fo -0.05 Y
24
Chapter 2 Calibration Procedures
Performance Verification Procedures
Amplifier Stability Check
This test verifies the stability of the voltmeter’s input amplifier by
measuring the rolloff of the frequency response at 40 MHz. The signal
measured for this test is a dc voitage taken at the rear-panel dc output
jack. This voltage is normalized to ~1 Vdc and 1s proportional to the
RMS input voltage (~1 Vdc corresponds to a full-scale meter deflection).
a HP 3400B Source Source DC Output
Range Output Voltage Output Frequency (DMM Reading)
0.1V 0.1 V 40 MHz ~065V to ~0.45V
1 HP 3400B: Select the 0.1 volt range.
2 Source: Select a 0.1 volt ac signal at 40 MHz.
3 External Multimeter: Select the 10 Vdc range with 5 digits of
resolution.
4 Verify that the de voltage measured at the rear-panel de output
jack 1s within the limits shown in the table above.
25
Chapter 2 Calibration Procedures
Performance Verification Procedures
Overload Protection Circuitry Check
This test verifies the volimeter's overload protection circuitry by
applying a voltage slightly greater than the range limit. The signals
measured for this test are dc voltages measured on test connector pin 8
(+VBB) and pin 9 (-VBB). At the end of the overvoltage sequence, the
input voitage is returned to 0.1 volts to ensure that the voltmeter will
recover to normal operation,
HP 34008 Calibrator Calibrator
Range Output Voltage Output Frequency +VBB Reading BB Heading
0,1 V ол У 1 kHz +11.5VY to +155 Y =15.5 V to -11.5V
9.1 V 0.4 V 1 kHz +1.0V to +50V 5.0 Y to ~1.0V
HP 3400B: Select the 0.1 volt range.
Calibrator: Select a 0.1 volt ac signal at 1 kHz (use the low
frequency output on the Fluke 5700A).
External Multimeter: Select the 10 Vdc range with 5% digits of
resolution,
Measure +VBB (pin 8 on the test connector) and -YBB (pin 9 on
the test connector). Verify that the measured voltages are within
the limits shown in the table above for a 0.1 volt output from the
calibrator,
Increase the calibrator’s output voltage from 0.1 volts to 0.4 volts
at 1 kHz.
Measure +VBB and -VBB. Verify that the measured voltages are
within the limits shown in the table above for a 0.4 volt output
from the cahbrator.
To ensure that the voitmeter will still operate properly, decrease
the calibrators output voltage from 0.4 volts to 0.1 volts.
Measure +VBB and -VBB. Verify that the measured voltages are
within the limits shown in the table above for a 0.1 volt output
from the calibrator.
26
Chapter 2 Calibration Procedures
Performance Verification Procedures
Crest Factor Check
This test verifies the voltmeter s crest factor performance. The signal
measured for this test is a dc voltage taken at the rear-panel de output
jack. This voltage is normalized to -0.9487 Vdc and is proportional to
the RMS input voltage (0.9487 Vdc corresponds to a full-scale meter
deflection).
ml 1 MS —
GV mm
ON mm
100 mS 7
HP 34008 Source DC Output
Range Configuration {DMM Reading)
0.3 V Vout=1.5 V, Offset=750 mV, =1.05 Y to -0.95 V
Pulse Output Width=1 mSec,
Frequency=10 Hz, Mode=Pulse
1 HP 3400B: Select the 0.3 volt range.
2 Source: Program the source to output a pulse train with the
following characteristics: Vout=1.5 volts, offset=750 mV,
pulse output width=1 mSec, frequency=10 Hz, mode=pulse.
3 External Multimeter: Select the 10 Vde range with 5% digits of
resolution.
4 Verify that the dc voltage measured at the rear-panel dc output
jack is within the limits shown in the table above.
27
Unapler 2 2 Calibration Procedures
Warning
Adjustment Procedures
The procedures in this section are used to adjust the voltmeter for peak
performance, For best performance, the voltmeter should always be
adjusted after repair. Do not perform the adjustment procedures unless
they are required. If you make unnecessary adjustments of the internal
controls, you may actually cause more difficulty.
Some procedures in this section must be performed with power applied
fo the voltmeter while the protective covers are removed. To avoid
personal injury or damage to the instrument, do not perform procedures
in this section unless you are qualified to do so.
Note Allow the voltmeter to warm up for 30 minutes, with the covers
in place, before atiempting any adjustments.
Front-Panel Meter Zero Adjustment
The zero adjustment screw is located on the voltmeters front panel.
If the meter pointer does not indicate zero when power has been turned
off for at least one minute, adjust the screw setting as described below.
1 Turn off the voltmeter and remove any input signals from the
front panel and any connections to the rear panel.
2 Allow one minute for the meter pointer to stabilize.
3 Rotate the zero adjustment screw clockwise until the pointer is to
the left of zero on the meter scale. Continue adjusting until the
pointer is at zero. If the pointer overshoots zero, repeat this step.
4 When the pointer is exactly at zero, rotate the adjustment screw
shightly counterclockwise to remove tension on the pointer's
internal mechanism, If the pointer moves to the left during this
adjustment repeat steps 3 and 4.
28
Chapter 2 Calibration Procedures
Adjustment Procad
Full Scale Gain Adjustment
This procedure manually adjusts the voltmeter for full scale readings.
The full scale adjustment and the tenth scale adjustment (described in
the next section) are interdependent and you should repeat the
adjustments until both measurements are within the recommended
limits.
The signal measured for this test is a dc voltage taken at the rear-panel
de output jack, This voltage is normalized to —1 Vdc and is proportional
to the RMS input voltage 1 Vdc corresponds to a full-scale meter
deflection).
For this adjustment, all measurements are made on the 0.01 volt range
at 1 kHz. You will make the full scale adjustments using R321 which is
located on the main circuit board (see below).
Full Scale
/ Gain Adjustment (R321)
E
esl —
5 — =
Cy
=
1 =
=
29
Chapter 2 Calibration Procedures
Adjustment Proced
НР 34008 Calibrator Calibrator DC Output
Hange Output Voltage Quiput Frequency (Dv iv Reading)
0.01 V 0.01 Y 1 kHz 1,0019 V to -0.9981 Y
1 FIP 3400B: Select the 0.01 volt range.
2 Calibrator: Select a 0.01 volt ac signal at 1 kHz (use the
“Wideband” output on the Fluke 5700A).
3 External Multimeter: Select the 10 Vde range with 5% digits of
resolution.
4 Remove only the top cover from the HP 34001 (it is important
that you do not remove the side or bottom covers). Adjust R321
until the de voltage measured at the rear-panel dc output jack is
within the limits shown In the table above.
Tenth Scale Gain Adjustment
This procedures manually adjusts the voltmeter for tenth scale
readings. The tenth scale adjustment and the full scale adjustment
(described in the previous section) are interdependent and you should
repeat the adjustments until both measurements are within the
recommended limits.
The signal measured for this test is a dc voltage taken at the rear-panel
de output jack. This voltage is normalized to —! Vdc and is proportional
to the RMS input voltage (-! Vdc corresponds to a full-scale meter
deflection).
For this adjustment, all measurements are made on the 0.01 volt range
at 1 kHz. You will make the tenth scale adjustments using R316 which
is located on the main circuit board (see next page).
30
Chapter 2 Calibration Procedures
Adjustment Procedures
Tenth Scale
Gain Adjustment (71316)
eal —
à} 000
| OL
(000
A
—
HP 3400B Calibrator Calibrator DC Output
Range Output Voltage Qutput Frequency (DMM Reading)
0.01 V 0.001 Y 1 kHz -0.1019 Y to -0.0981 Y
1 HP 3400B: Select the 0.01 volt range.
2 Calibrator: Select a 0.001 volt ac signal at 1 kHz (use the
“Wideband” output on the Fluke 5700A).
3 External Multimeter: Select the 10 Vdc range with 51 digits of
resolution.
4 Remove only the top cover from the HP 3400B Gt is important
that you do not remove the side or bottom covers). Adjust R316
until the de voltage measured at the rear-panel de output jack is
within the limits shown in the table above.
starting with step 1 for the full scale adjustment, on page 30,
Note Since the full scale and tenth scale adjustments are interdependent,
you should repeat both adjustments again. Repeat the procedures again,
31
Chapter 2 Calibration Procedures !
Adj ustment Proced ;
Full Scale Pointer Adjustment
This procedure shows you how to manually adjust the position of the
meter pointer for full scale readings. When properly adjusted, the meter
pointer should be aligned with the full scale marking on the right side
of the meter scale.
This adjustment is made on the 0.1 volt range at 1 kHz, You will use
R330 which is located on the main circuit board to make the adjustment
(see below).
Full Scale
/ Pointer Adjustment (R330)
—
1 HP 34008: Select the 0.1 volt range.
2 Cahbrator: Select a 0.1 volt ac signal at 1 kHz (use the
“Wideband” output on the Fluke 5700A).
3 Allow one minute for the meter pointer to stabilize.
4 Remove only the top cover from the HP 3400B (it is important
that you do not remove the side or bottom covers). Adjust R330
until the meter pointer is aligned with the full scale marking on
the right side of the meter scale.
32
Chapter 2 Calibration Procedures
Adjustment Procedures
20 MHz Flatness Adjustment
This procedure manually adjusts the 20 MHz flatness. The adjustment
is made with a 100 mV signal applied at 20 MHz. You will make the
flatness adjustment using C304 which is located on the main circuit
board (see below).
The signal measured for this test is a de voltage taken at the rear-panel
dc output jack. This voltage is normalized to —1 Vdc and is proportional
to the RMS input voltage (-1 Vdc corresponds to a full-scale meter
deflection).
20 MHz Flainess
| Adjustment (C304)
О са
HP 3400B Calibrator Calibrator DE Output
Range Output Voltage Output Frequency (DMM Reading)
0.1V 01V 20 MHz 1.0125 Y to -0.9875 V
1 HP 34008: Select the 0.1 volt range.
2 Calibrator: Select a 0.1 volt ac signal at 20 MHz (use the
“Wideband” output on the Fluke 57004).
3 External Multimeter: Select the 10 Vdc range with 51% digits of
resolution.
4 Remove only the right-side cover from the HP 3400B (as viewed
from the front panel). It is important that vou do not remove the
left-side, top, or bottom covers. Adjust C304 until the voltage
measured at the rear-panel dc output jack is within the limits
shown in the table above.
33
Chapter 2 Calibration Procedures
Input Attenuator Adjustment
This procedure performs a manual adjustment of the input attenuator
at 50 Hz and 100 kHz. First, you will make the low frequency
adjustment at 3V/50 Hz using R123 on the main circuit board (see
below). You will make the high frequency adjustment at 3V/100 kHz
using C134 on the main circuit board (see below).
The signal measured for this test is a de voltage taken at the rear-panel
dc output jack. This voltage is normalized to -0.9487 Vdc and is
proportional to the RMS input voltage (-0.9487 Vdc corresponds to a
full-scale meter deflection).
| |
CO ld TT
= «> >
= |
Bo >
Cm
High Freguency
7 Adjustment (C134)
O lw Low Frequency
Adjustment (R123)
34
Chapter 2 Calibration Procedures
Adjustment Procedures
HP 3400B Calibrator Calibrator DC Output
Range Output Voltage Output Frequency {DMM Reading)
3V 3V 50 Hz 0.950 V to 0.947 V
ЗУ ЗУ 100 kHZ 0,950 V to —0.947 V 7
Low Frequency 1 HP 3400B: Select the 3 volt range.
2 Calibrator: Select a 3 volt ac signal at 50 Hz (use the “Wideband”
output on the Fluke 5700A).
3 External Multimeter: Select the 10 Vdc range with 514 digits of
resolution.
4 Remove only the right-side cover from the HP 3400B (as viewed
from the front panel). It is important that you do not remove the
left-side, top, or bottom covers. Adjust R123 until the voltage
measured at the rear-panel de output Jack is within the Hmits
shown in the table above for 50 Hz,
High Frequency 1 HP 3400B: Select the 3 volt range.
2 Calibrator: Select a 3 volt ac signal at 100 kHz (use the
“Wideband” output on the Fluke 5700A).
3 External Multimeter: Select the 10 Vdc range with 5 digits of
resolution,
4 Remove only the right-side cover from the HP 34008 (as viewed
from the front panel). It is important that you do not remove the
left-side, top, or bottom covers. Adjust C134 until the voltage
measured at the rear-panel de output jack is within the limits
shown m the table above for 100 kHz.
30
Chapter 2 Calibration Procedures
Test Connector Pinout
Test Connector Pinout
Test connector J3 gives you access to several test points on the main
circuit board. You can build your own custom ribbon cable interface if is
convenient for your application. The table below shows the pinout for
the test connector. Refer to the schematics in chapter 7 for more detailed
information on the circuitry thai interfaces with the test connector.
Pin Number
Description
UD E + С) EEN —
K1018, Relay Drive Logic for Relay K101 (low true, see the table on page 45).
K201B, Relay Drive Logic for Relay K201 (low true, see the table on page 45).
K2028, Relay Drive Logic for Relay K202 (low true, see the table on page 45).
K203B, Relay Drive Logic for Relay K203 (low true, see the table on pags 45).
Remote/l.ocal Control, Ground or Hold Low to Disable Range Selector Switch,
+VCC {4.7 KQ Series Resiston,
CGND, Common Ground
+VBB
-\/ВВ
VRAW (10 KQ Series Resistor), Output from Power Transformer (T1).
Not Used
OPAMP_DC, Output rom Wideband Amplifier (U201).
DC_OUT, Same as Rear Panel Output (loading on this line will affect signal on
rear-panei output; loading on rear-panel output will affect signal on this line).
CGND, Common Ground
36
Theory of
Operation
Theory of Operation
This chapter 1s organized fo provide descriptions of the circuitry
contained on each schematic shown in chapter 7. A block diagram
overview is provided followed by more detailed descriptions of the
circuitry contained in the schematics chapter.
e Block Diagram 39
e Input Attenuator 41
e Impedance Converter 41
e Post Attenuator 42
¢ Wideband Amplifier 42
¢ Chopper Op Amp / Thermocouple Pair 43
s Power Supplies 44
e Switch Board 45
38
PA AE
Chapter 3 Theory of Operation
Block Diagram
Block Diagram
Referring to the instrument block diagram shown below, you can see
that the voltmeter's operational circuitry consists of two attenuators,
an impedance converter, a wideband amplifier, a chopper op amp,
a thermocouple pair, and a direct reading meter,
Thermocouple
„== = = — = — — „бен a > Pair
Da
„”
#
ой ий
Input Impedance Posi
| Attenuator Converter Attenuator
| Q121 and
| 0122
LI Chopper |
34008 Block Diagram
39
Chapter 3 Theory of Operation
Block Diagram
A signal being measured is applied to the input attenuator through the
input connector, located on the voltmeter s front panel. The input
attenuator has an input impedance of 10 MQ and provides two ranges
of attenuation. The output of the input attenuator is applied to the
impedance converter. The impedance converter is a non-inverting unity
voltage gain amplifier. It presents a high impedance to the input signal
and provides a low impedance output to drive the post attenuator. The
post attenuator provides six ranges in a 1, 3, 10 sequence. The two
attenuators are switched to provide 12 ranges of attenuation.
The output of the post attenuator is amplified by the wideband
amplifier. The wideband amplifier is a two-stage amplifier (U301 and
U302), The ac output of the wideband amplifier is amplified to drive one
of the thermocouples in the thermocouple pair (TC301).
The de output of TC301 is applied to the chopper op amp (U303) which
modulates the voltage. The resultant modulated signal is then
amplified and, after the amplification, the signal is demodulated back
to a de voltage. This voltage is the output of the chopper op amp. The
value of the voltage is proportional to the de input voltage.
The output of the chopper op amp is applied to a filter and also to the
second thermocouple of the thermocouple pair (TC301). The output of
the filter is applied to a dc output amplifier (U304C) which is used to
drive the meter (MI).
The thermocouple pair (TC301) acts as a summing point for the ac
output of the wideband amplifier and the de output of the chopper
op amp. The difference in the heating effect of these voltages is the de
input to the chopper op amp. This difference input is amplified and is
fed to TC301 and also, after going through the output amplifier (U3040),
to the meter (M1), This voltage represents the RMS value of the ac
signal applied to the input connector. By using a “matched”
thermocouple pair and measuring the difference, the output of the
chopper op amp will be linear. Using a matched thermocouple pair also
provides temperature stability.
40
Chapter 3 Theory of Operation
input Attenuator
Input Attenuator
The input attenuator is a capacitive-compensated attenuator which
provides two ranges of attenuation for the 12 positions of the Range
selector switch. When the selector switch is positioned to one of the six
most sensitive ranges (1 mV to 300 mV), the attenuator output voltage
is equal to the input voltage. When the selector switch is positioned to
one of the six higher ranges (1 V to 300 V), the input signal is
attenuated 60 dB (1000:1 voltage division) by the resistive voltage
divider consisting of R121, R122, and R123. Trimmer C134 is adjusted at
100 kHz, and R123 is adjusted at 50 Hz to provide constant attenuation
over the input frequency range.
Impedance Converter
‘The impedance converter uses a FET-follower circuit to match the high
output impedance of the input attenuator to the low input impedance of
the post attenuator. The FET-follower circuitry has unity gain with no
phase inversion between the input and output signals.
The ac input signal to the impedance converter is resistor/capacitor
coupled via R127 and C149 to the gate of FET Q121. The output of the
converter is developed across Q122 which acts like a variable load
resistor for the FET,
‘The bootstrap circuitry, consisting of C152 and R130, increases the input
impedance of the converter circuitry and the compensating feedback
circuitry, consisting of C151, decreases the output impedance of the
converter. The bias voltage for Q122 is developed by resistors R133,
CR125, R134, and R140.
41
Chapter 3 Theory of Operation
Post Attenuator
Post Attenuator
The post attenuator is a resistive divider which attenuates the ac input
signal while maintaining a low impedance output for the following
amplification stages. The ac input signal is applied to a precision
resistive voltage divider. These resistors are arranged to give six ranges
of attenuation at 10 dB per range. The six ranges of the post attenuator
combined with the two ranges of the input attenuator make up the
12 ranges of attenuation (I mV to 300 V).
Wideband
The wideband amplifier provides constant gain to the ac signal being
measured over the entire frequency range of the HP 3400B. The
wideband amplification required to drive the thermocouple heater is
provided in two gain stages. The first stage has a gain of 36 dB and
consists of a differential transistor pair Q301 and Q302 driving U301.
This gain stage also includes the capacitor feedback adjustment (C304)
to adjust the voltmeter's frequency response at 20 MHz. The second
stage has a gain of 14 dB to the thermocouple heater and consists of U302.
Amplifier
The combined gain of 50 dE amplifies the 1 mV RMS full-scale input
signal to 316 mV RMS applied to the thermocouple heater. The nominal
resistance of the heater is 90£2 and there is 3.5 mA RMS of current,
flowing at full-scale input signal.
Protection against excess current to the thermocouple heater is
provided by controlling the power supply voitages to the heater drive op
amp (U302). The output from U302 is peak-detected by CR306 and CR307
and is then averaged with an RC network. The average de level is
compared with a reference by comparators U304A and U304B. The
comparator output lowers the supply voltage via Q303 and Q304 when
the average dc level exceeds the reference level, The average de level of
the input signal allows for 10-to-1 crest factor signals to be applied to
the heater at proper levels without being attenuated.
42
Chapter 3 Theory of Operation
Chopper Op Amp / Thermocouple Pair
Chopper Op Amp / Thermocouple Pair
The chopper op amp and the thermocouple pair form a servo loop which
functions to position the direct reading meter (M1) to the RMS value of
the ac input signal. The wideband amplifier output is applied to the
heater of thermocouple pair (TC301). The ac voltage causes a de voltage
to be generated in the resistive portion of TC301 which is proportional to
the heating effect (RMS value) of the ac input. The de voltage is applied
to the chopper op amp.
The chopper op amp circuitry consists of a chopper op amp (U303),
filter, and output amplifier (U304C). The chopper op amp is a high-gain,
low-drift op amp and is used to modulate the applied de voltage,
amplify the voltage, and then demodulate the voltage back to a de
voitage (the output voltage of the amplifier). The output of the amplifier
18 the ac stabilizing and summing feedback for the thermocouple pair
(TC301), and is also applied to the filter. The ac stabilizing feedback
(using R323, R320, and C309) is used to prevent the circuitry from
oscillating.
The output from the chopper op amp (summing feedback) is applied to
the heating element of thermocouple pair (TC301). The dc voltage
developed in the resistive portion of TC301 is effectively subtracted from
the voltage developed by TC301. The input signal to the chopper op amp
then becomes the difference in the de outputs of the two thermocouples.
When the difference between the two thermocouples becomes zero, the
dc output from the chopper op amp will be equal to the ac output from
the wideband amplifier,
The low pass filter, consisting of R325, R326, C312, C313, and U304C,
18 used to further reduce the noise on the output of the chopper op amp.
This is to make the meter reading quiet.
The output of the low pass filter and output amplifier (U304C) drives
the meter (M1) and the DC Out connector on the rear panel. The rear
terminal's output impedance 1s approximately 10000.
43
Chapter 3 Theory of Operation
Power Supplies
Power Supplies
The power supplies provide dc operating voltages for the circuitry used
in the HP 34008. The input line power is applied to an input line
module, The module contains a line filter, a fuse, the line switch, and
voltage tap selection for the power transformer. Four line voltages
selections are available: 100, 120, 220, 240 Vac.
The outputs from the power transformer drive three voltage regulators.
The voltages produced by the three voltage regulators ave: +27 Vdc,
-15 Vde, and +5 Vde. The +27 Vdc supply is used to power the
impedance converter Q121 and Q122. The +27 Vdc supply is also
dropped by a 12 volt zener diode (CR112) to develop +15 Vde for U302
through overload regulator Q303. In addition, the +27 Vdc supply is
regulated by a 15 volt zener diode (CR111) for U301 and U304. The de
chopper amplifier is powered by temperature-compensated 6.2 volt
zener diodes (CR113 and CR114) to provide a stable dc source to U303
and its associated circuits. The +5 Vdc supply is used to power the logic
circuitry and attenuator relays.
44
Chapter 3 Theory of Operation
Switch Board
Switch Board
The switch control circuitry is located on the small circuit board which
is connected to the front-panel Range selector switch. The Schottky
diodes (CR41 through CR60) on the switch board provide the appropriate
relay logic for the relay drivers on the main circuit board (see table
below). The switch board connects to the main circuit board using a
ribbon cable (P1). The switch board also provides the interface for
wiring to the meter mechanism, the front-panel power LED, and the
rear-panel DC Out connector.
Voltage Hands Ki01 K201 K202 and K204 K203
0.001 0 о 0 1
0.003 0 1 0 1
0.01 0 O 0 О
0.03 O 1 0 0
0.1 O O 1 1
0.3 0 O 1 0
1.0 i O 0 1
3.0 1 i 0 1
10.0 1 O 0 0
30.0 1 1 0 O
100.0 i о 1 1
300.0 1 O 4 o
O = Relay De-Energized; 1 = Relay Energized.
45

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