Keithley 6512, Instruction Manual, Page: 92 / 156

Performance Verification
5-2
• Keithley Model 6171 3-slot male to 2-lug female triax
adapter.
• Single banana cable.
• Keithley Model CAP-31 protective cap/shield for IN-
PUT connector.
5.5 Verification procedures
The following paragraphs contain procedures for verifying in-
strument accuracy with each of the four measuring functions:
volts, ohms, amps and coulombs using a Model 263 Calibra-
tor/Source. Using the Model 263 to verify Model 6512 simpli-
fies the procedure and eliminates tedious characterization
procedures and the need to build a special test fixture.
These procedures are intended for use only by qualified per-
sonnel using accurate and reliable test equipment. If the in-
strument is out of specifications, refer to Section 7 for
calibration procedures, unless the unit is still under warranty.
WARNING
The maximum common-mode voltage
(voltage between input low and chassis
ground) is 500V. Exceeding this value
may cause a breakdown in insulation,
creating a shock hazard. Some of the
procedures in this section may expose
you to dangerous voltages. Use standard
safety precautions when such danger-
ous voltages are encountered.
CAUTION
The maximum voltage between the high
and low input terminals is 250V (10 sec-
onds maximum on the mA ranges). In-
strument damage may occur if this
value is exceeded.
NOTE
Verify performance in the order listed: in-
put current, amps, coulombs, volts, and
ohms. Input current may remain high for
several minutes following measurement of
high volts or ohms. Place the V,
Ω
GUARD switch in the OFF position un-
less otherwise noted.
5.5.1 Input current verification
Perform input current verification as follows:
NOTE
The following procedure must be performed
at an ambient temperature of 23°C ±1°C.
1. Disconnect all cables from the Model 6512 input.
2. Place the CAP-31 input cap on the INPUT connector.
3. Select the amps function, 2pA range, enable zero check,
and then enable zero correct.
4. Connect a jumper between the rear panel COM and
chassis ground terminals.
5. Disable zero check, and allow one minute for the read-
ing to stabilize.
6. Verify that the reading is 50 counts or less (within
50fA). Enable zero check.
7. Remove the jumper connected between the COM and
chassis ground terminals.
5.5.2 Amps verification
Connect the Model 6512 to the Model 263, as shown in Fig-
ure 5-1, and perform amps verification as follows:
1. Enable Model 6512 zero check, and select the 20mA
range. Do not use auto-range.
2. Check that the display reads 0.000 ±1 count. If not, en-
able zero correct.
3. Using the AMPS (active) current source mode, program
the Model 263 to output 19.0000mA to the Model 6512.
4. Disable zero check, and verify that the reading on the
Model 6512 is within the limits in Table 5-1.
5. Using Table 5-1 as a guide, repeat steps 1 through 4 for
the 2mA through 2nA current ranges.
6. Using the AMPS V/R (passive) current source mode of
the Model 263, repeat steps 1 through 4 for the 200pA
through 2pA ranges.