Dc Volts Verification; Dc Amps Verification; Table; Limits For Dc Volts Verification - Keithley 6517 Service Manual

Performance Verification
Do not connect test equipment to the
Model 6517A through a scanner or other
switching equipment.
1.9.1 DC volts verification
DC voltage accuracy is verified by applying accurate DC
voltages from a DC voltage calibrator to the Model 6517A
INPUT jack and verifying that the displayed readings fall
within specified ranges.
Follow the steps below to verify DCV measurement
accuracy.
1. Connect the Model 6517A to the calibrator, as shown in
Figure 1-1. Be sure to connect calibrator HI to Model
6517A INPUT HI and calibrator LO to the Model
6517A INPUT LO using the low-noise coax cable,
BNC-to-dual banana plug adapter, and the triax-to-BNC
adapter as shown.
2. Turn on the Model 6517A and the calibrator, and allow
a one-hour warm-up
measurements.
3. Restore Model 6517A factory default conditions, as
explained in paragraph 1.7.
4. Select the Model 6517A 2V DC range, and make sure
the filter is enabled.
Do not use auto-ranging for any of the ver-
ification tests because auto-range hystere-
sis may cause the Model 6517A to be on
an incorrect range.
5. With zero check enabled, press REL to zero correct the
instrument.
6. Set the calibrator output to 0.00000VDC, and disable
zero check. Allow the reading to settle completely
before continuing.
7. Enable the Model 6517A REL mode. Leave REL en-
abled for the remainder of the DC volts verification
tests.
8. Set the calibrator output to +1.90000VDC, and allow the
reading to settle.
9. Verify that the Model 6517A reading is within the limits
summarized in Table 1-5.
10. Repeat steps 8 and 9 for the 20V and 200V ranges using
the test voltages listed in Table 1-5.
11. Repeat the procedure for each of the ranges with nega-
tive voltages of the same magnitude as those listed in Ta-
ble 1-5.
1-6
NOTE
period before
NOTE

Table 1-5

Limits for DC volts verification
6517A
DCV
range
2V
20V
200V
1. Repeat procedure for negative voltages of same magnitude.
2. Reading limits shown are calculated only from Model 6517A one-
year accuracy specifications and do not include test equipment
uncertainty.
1.9.2 DC amps verification
DC amps accuracy is checked by applying accurate DC cur-
rents to the instrument INPUT jack and then verifying that
the current readings fall within appropriate limits. Note that
two separate current verification procedures are provided
because of the different equipment required. Basically, the
amps verification procedures are divided into the following
making
two groups:
• 20pA – 2µA range verification using a DC voltage cal-
ibrator and the Keithley Model 5156 Electrometer Cal-
ibration Sandard, which contains standard resistors.
• 20µA – 20mA range verification using a DC current
calibrator.
20pA–2µA range verification
Accuracy of the 20pA-2µA ranges is verified by applying
accurate currents derived from DC voltages and resistance
standards, and then checking the displayed readings against
calculated limits. Note that it is necessary to calculate read-
ing limits for each range separately from the exact values of
the resistance standards supplied with those standards.
Follow the steps below to verify measurement accuracy of
the 20pA to 2µA ranges.
1. Connect the Model 6517A to the DC voltage calibrator
and the calibration standards box, as shown in Figure
1-2. Initially, make connections to the calibration stan-
dard using the 100G Ω resistor.
It is not necessary to connect the calibra-
tion standard to the Model 6517A DIGI-
TAL I/O port when performing the
verification procedures.
Applied DC Reading limits
voltage (18° to 28°C, 1 year)
1.90000V 1.89949V to 1.900515V
19.0000V 18.9950V to 19.0050V
190.000V 189.883V to 190.117V
NOTE