Technical data

3 Calibration
32 U2761A Service Guide
5 Proceed to output impedance adjustment or exit the
calibration mode when necessary.
Output Impedance Adjustment
The U2761A stores the calibration constant for output
impedance. The output impedance measurement is necessary
to calculate the correct output amplitude when the load
impedance is not at High-Z termination. The output
impedance is measured at three different output paths.
1 Set the DMM to measure offset-compensated, four-wire
ohms. Set the DMM to use 100 NPLC integration. Connect
the DMM to the U2761A as shown in the figure below.
Figure 3-5 U2761A to DMM four-wire connection
2 Use the DMM to make the resistance measurement at the
output terminal for each setup shown in the table below.
The expected measured value is approximately 50
Ω..
3 Make sure the Offset Compensation setting in the DMM is
switched on.
4 Enter the measured value to the U2761A as described in
“Calibration Procedure” on page 30.
Table 3-11 Output impedance adjustment configuration
U2761A DMM
Setup Output path Lower margin Measurement Upper margin
5
–20 dB 49.5 ΩΩ50.5 Ω
60 dB 49.5 ΩΩ50.5 Ω
7
1
+20 dB 49.5 ΩΩ50.5 Ω