Keithley 610C, Instruction Manual

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b. To check these resistors, it is necessary to use
a bridge capable of better than 1% accuracy up to lOll
ohms such as the Keithley Instruments Mode15l5A Megohm
Bridge. If such equipment is not available, two pro­
cedures are recommended to check out the resistors:
1. Return t�e complete instrument to the factory
for resistor calibration.
2. Replace the high-megohm resisters periodically
with a certified set from Keithley Instruments to
assure absolute calibration accuracy.
6-11. ACCURACY CHECK.
a. Checking the accuracy is the quickest way to
spot faulty Model 6l0C operation. Perform the check
about once a year, if components are replaced, or if
other adjustments are made. If accuracy is verified
over all ranges, the Model 6l0C should be able to meet
all specifications. If the accuracy must be checked
often, check the stability.
b. Connect the Model 6l0C input to the
Model 241 and monitor the output with the Model 160
DVM.
First, set the Model 6l0e for the 10-volt range.
Increase the input voltage in I-volt steps from 0 to
10 volts. The Model 6l0e should indicate the input
voltage to ±l% of full scale.
Perform the same oper­
ation in the 3-volt range. Connect the Model 610e to
the Model 260.
Check the other voltage ranges for
accuracy of ±l% of full scale. Make sure the 3V-lMA
Switch is in the 3V position for the 1, 3 and 10 volt
ranges
NffiE
In subparagraph c below, for 10-1 ampere
through 10-5 ampere ranges, a larger Multi­
plier Switch setting will result in inaccu­
racies due to loading of the current source;
hence the .01 Multiplier Switch setting must
be used. The appropriate current source is
two decades less than range setting; that is,
on the 10-1 ampere range use 10-3 ampere
source, etc.
c. Current. Connect the Model 6l0e to the Model
261 with the Model 2611 and monitor the output with
the Model 160 DVM.
Check the full-scale accuracy of
all the current \,ositions on the Range Switch. For
the 10-6 to 10-1 ampere ranges, set the FEEDBACK
Switch to FAST and the Multiplier Switch to 1. The
Model 610C should indicate the input current to =2% of
full scale from 10-6 to 10-8 am\,ere ranges and ±4% of
full scale from the 10-9 to 10- 1 ampere ranges.
For
the ranges above 10-5 ampere, construct a current
source whose output is ±0.2S%. Set the Model 610C
FEEDBACK Switch to NORMAL and the Multiplier Switch to
.01 when calibrating these ranges.
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d. Ohms. Connect the hig� side of the Model 5155
Resistor-to the center terminal of the INPUT Receptacle
and the low side to low. Check the full scale accuracy
of all ohm pOSitions on the Range Switch by measuring
the voltage drop of the known current across· the known
sample with the Model 6l0C. The test current applied
is the reciprocal of the OHMS Range Setting.
Check
the
Ion
through 108 ohm ranges for an accuracy of ±3%
of full scale by using the resistance measurement meth­
od as described in paragraph 2-5b
Switch in
NORMAL). Check the 109 through ohm ranges for an
accuracy of ±5% of full scale by employing the resis­
tance measurement method as described in paragraph 2-Sc
(FEEDBACK Switch in FAST).
e. Coulombs. To check the Model 610e as a charge
amplifier, set the FEEDBACK Switch to FAST. Apply 10
volts from the Keithley Model 241 Voltage Supply
through a Keithley Model 5155 lOll ohm standard to the
Model 6l0C input. Set the Multiplier Switch to the
settings given in Table 9.
Use a stop watch or a Tek­
tronix Model 561A Oscilloscope to time the rise to
full scale deflection. Check each range to ±5%.
TABLE 9.
Coulomb Ranges Accuracy Check. The Table gives the
Multiplier Switch setting, the coulomb range checked
and the rise time for each coulomb range.
Multiplier Switch
Setting
.01
.1
1
10
6-12. UNITY GAIN CHECK.
Coulombs
Range
Rise Time, Zero
to Full scale
(seconds)
10
10
10
10
a. Zero check the Model 610e and set.the instrument
to the 100 volt range. Connect the Model 241 Voltage
Supply to the Model 610C INPUT Receptacle and to the
Model 662 Differential Voltmeter High terminal. Con­
nect the Electrometer Xl OUTPUT Terminal to the Low
terminal of the Model 662. Set the Model 662 dial to
o
and the Null Switch to 10 millivolts. The Model 662
should indicate at or near zero.
NOTE
A large transient is generated when the 241
is switched from Standby to Output. To pre­
vent false indication, set.241 to Output and
use voltage dial (0 or 10 volts) when making
this check.
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