720A Operation and Maintenance Manual – Rev S – January 25, 2019
Page 27
13231 Rooster Springs Rd.,
Austin, TX 78737
T: (512) 858-4045 E: info@amptec.com
Trim pot at RV1: Influences full-scale on all ranges.
Trim pot at RV2: Influences zero-scale on all ranges.
Trim pot at RV5: Influences zero-scale on 200 mΩ range.
Trim pot at RV6: Influences full-scale on 200 mΩ range.
All other trim pots on the board, including RV3 and RV201 shown in Figure 9, are not
used during standard product recalibration and should not be adjusted during this
procedure.
E-4.3 Calibration Procedure Adjustments
This section contains information on the specific adjustments necessary to calibrate a
720A meter. Ensure that you have first followed the instructions detailed in the
calibration procedure overview in section X before completing any of the internal
adjustments below. It is recommended that you complete the following steps in order.
1. Zero Adjustment: Select the 200 Ω range. Connect the meter via the
measurement test leads across a precision 1.0 Ω
resistance standard with ± 0.005% or better accuracy.
Adjust the trim-pot (RV2) to make the meter read 1.00
Ω (100 counts on the display). Note that this process
will be repeated on the 200 mΩ range with a 0.001 Ω
standard after the full-scale adjustment is performed.
2. Full-Scale Adjustment: Connect the meter via the measurement test leads
across a precision 100 Ω resistance standard with ±
0.005% or better accuracy. Adjust the full-scale pot
(RV1) to make the meter read 100.00 Ω (10000
counts on the display).
3. 200 mΩ Adjustment: Next, the 200 mΩ range needs to be calibrated. The
trim pots adjusted above (RV1 & RV2) affect every
range of the meter, while RV5 & RV6 only affect the
200 mΩ range. Therefore, they must be adjusted last.
4. 200 mΩ Zero Adjustment: Select the 200 mΩ range. Connect the meter
via the measurement test leads across a precision
0.001 Ω resistance standard with ± 0.01% or better
accuracy. Adjust the trim-pot (RV5) to make the meter
read 01.00 mΩ (100 counts on the display).
5. 200 mΩ Full-Scale Adjustment: Connect the meter via the measurement test leads
across a precision 100 mΩ resistance standard with ±
0.005% or better accuracy. Adjust the full-scale pot
(RV6) to make the meter read 100.00 mΩ (10000
counts on the display).
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