Adjustment and Verification
Routine Adjustment
6
Initial Setup and Connections
1. On the 8508A, select
CLEAR, Pwr Up Dflt to select DCV 1kV range.
2. Ensure that the calibrator output is set to
STANDBY and configured for Internal
Guard (
EX GRD is deselected).
3. Connect the calibrator to the 8508A as shown above in Figure 6-1.
Note
After making the connections allow at least 30 minutes for thermal emfs in
the leads to stabilise.
4. On the calibrator select zero Ω and
OPR to operate the output.
Select
EX SNS.
5. In calibration mode the resolution defaults to
RESL7 in the resistance function. It is
recommended that this resolution is used for adjustment of all resistance ranges.
HiVΩ is restricted to RESL6.
6. Confirm the 8508A is configured for internal guard (External Guard is deselected) by
checking that the ExGd legend does not appear on the left hand display.
Normal
Ω
Mode Adjustment
1. Press the
CAL key. Press the Ω key and select 2 Ω range.
2. Press the
CONFIG key and deselect Filt. Ensure LoI is deselected. Ensure 4 WΩ is
selected.
Range Zero and Gain Adjustment Procedure
After the initial setup and connecting up, use the following procedure to adjust range zero
and range gain for the ranges and points detailed in Table 6-5 for the Normal Ω mode.
For the 2 GΩ range use the 1 GΩ standard resistor in place of the calibrator. Just one
range can be adjusted if required, but for a full-adjustment start with the 2 Ω range and
work up to the 2 GΩ range.
Note that EX SNS (4-wire) is not available on the 5720A 100 MΩ range, and the 8508-
7000K 1 GΩ standard resistor is used as a 2-wire device with the calibrator 2-wire
resistance zero used for the corresponding zero points. Ensure
4WΩ is deselected on the
8508A when adjusting the 200 MΩ and 2 GΩ range, range zero, and range gain points.
On each range, the 8508A automatically recognizes the appropriate value as range zero or
range gain from the applied resistance value.
Note
It is unlikely that the resistance standard will be at exactly the nominal value
required. The Set feature allows a user to enter the true output value of the
calibration standard where it differs from nominal range gain point. If the
resistance value is exactly the nominal value required, omit step 6 for the
Range Gain Point.
6-21
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