Keithley 610C, Instruction Manual

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SECTION 6.
6-1. GENERAL.
8.
The function of the calibration section is to
provide a method of che�king the Model 610e to make
sure that it operates properly and within the specifi­
cations given in Table 1 on page ii.
h.
The following procedures ar� recommended for ad­
justing and calibrating the Model GIOC. Use the equip­
ment recommended in Table 6 or their equivalents.
6-2. CALIBRATION SCHEDULE.
8.
Check offset current (paragraph 6-8) at regular
intervals to make sure the input transistors are func­
tioning correctly.
b. Verify the value of the high-megohm resistors
(paragraph 6-10) approximately every six months_
c. Calibrate the ohms ranges (paragraph 6-11) about
once a year or when range resistor or power supply
c�ponents are replaced.
d. Calibrate the meter zero (paragraph 6-4) about
once a year or when components are replaced.
e.
Check the Model 6l0C accuracy (paragraph 6-11)
once a year, after the other adjustments, or if im­
proper operation is suspected.
NOTE
Unless otherwise stated all the following
calibration procedures will be made with the
FEEDBACK Switch set to NORMAL and the 3V-lMA
Switch set to 3V,
6-3. PRELIMINARY CALIBRATION PROCEDURES.
a. Do not connect the Electrometer to an ac power
line. Set the front panel controls as follows:
ZERO CHECK Button LOCK
RANGE Switch
VOLTS
"Multiplier Switch
100
FEEDBACK Swi tch
NORMAL
METER Switch POWER OFF
b. Adjust the meter mechanical zero.
c. Plug the Electrometer into a 117 or 234 volt ac
line and turn the instrument on. Make sure the unit
is zero checked.
1, If the instrument is operative, the meter
should be on scale. Decrease the Multiplier Switch
setting in steps to the 1 millivolt range and zero
the E�ectrometer on each range with the ZERO Controls.
2. If inoperative, meter pinned, etc., check the
power supplies before troubleshooting for other than
an obvious problem.
d. Check the power supply voltages as called out in
the troubleshooting procedures, paragraph 5-5 d.
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CALIBRATION
6-4. MECHANICAL METER SET AND METER ZERO CALIBRATION.
Zero whenever other adjustments are made.
a. To set the mechanical Zero meter, turn the METER
Switch to METER OFF and set the mechanical Zero Meter
adjustment for zero meter reading (top-scale zero).
b. To calibrate meter zero:
1. rurn the Model 6l0e on. Zero the meter on the
.001 Multiplier Switch setting. Then set the Mul­
tiplier Switch to 1; apply 1 volt %0.05% with the
Keithley Model 260 Nanovolt Source to the Model 610C
INPUT Receptacle.
Monitor the output with Keithley
Models 160 or 163DVM and a 3:1 adapter. Adjust the
FINE ZERO Control for 1.000 volt at the output. Ad­
just the METER CAL Potentiometer, Rl79 for full
scale meter reading.
2. Set the center zero by first zeroing the meter
on .the .001 Multiplier Switch setting. Then switch
to the 1 position.
Set the METER Switch to CENTER
ZERO and adjust the Meter Ctr. Cal. potentiometer,
Rl83, for exact center-scale meter zero.
6-5. CALIBRATION OF OHMS RANGES. This calibration
adjusts the constant power supply needed for resis­
tance measurements.
It must be accurate to maintain
specified resistance measurement accuracy.
a. Connect the Model 662 to the junction of resis­
tors R188 and R136 and the cornman lead to the unity­
gain terminal (Figure 2). Adjust the Ohms Cal Poten­
tiometer, R137, for 1 volt dc ±0.5%.
b. If the control does not have enough latitude,
check the
+9
volt supply (paragraph 5-5).
6-6. TRACKING CHECK AND lMA OVTPul CALIBRATION.
a. Set the METER Switch to
+,
the Multi­
plier Switch to 1 and apply
I
volt with the Model 260
to the INPUT Receptacle.
1. If the 1 volt range has good accuracy, the
meter should indicate full scale. If not, use the
.1 or 10 Multiplier Switch settings, whichever has
the best full scale accuracy.
2.
Check the meter 0-10 scale for no more than
1/2% (1/2 division) tracking error going from zero
to full scale in 1/10 of full scale voltage steps.
b.
INA
Output. Load output of the Model 610C with
a 1400 ohm resistor.
1.
Set the 3v-lMA Switch to lMA, the Multiplier
Switch to 1 and apply 1 volt to INPUT Receptacle
with the Model 260.
2. Adjusting the lMA CAL Control (R177) should
vary the output voltage from 1.33 to 1.47 volts,
indicating a current variation from 0.95 to 1.05
milliamperes.
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