4-5 DC Reference Calibration Chapter 4 — Adjustment
4-2 PN: 13000-00164 Rev. K ML248xx, ML249xA MM
4-5 DC Reference Calibration
To calibrate the DC Reference:
1. Enter the power meter Service Mode by pressing the front panel keys as follows:
System | Service | Diag | 0 | Enter
2. Set the DSP cal number to 6 by pressing the front panel keys as follows:
DSP Diag Commands | Sel | 6 | Enter | Send Command
3. Connect a DVM between ZTP17 (gnd) and ZTP205 (+V) on the Measurement PCB. See Figure 4-1
on page 4-3.
4. Measure and record the reading displayed on the DVM in mV. If the reading is a negative value, change
the minus (–) to a plus (+).
Example: If reading = –0.004 V, change to +0.004 V.
5. Subtract the positive reading from Step 4 from 1 V and record this result.
Example: If reading from Step 4 = 0.004 V
1.000 V – 0.004 V = 0.996 V
6. Set the DSP cal number to 5 by pressing the front panel keys as follows:
Sel | 5 | Enter | Send Command
7. Connect a DVM between ZTP17 (gnd) and ZTP205 (+V) on the measurement PCB as shown in
Figure 4-1.
8. Adjust pot R353 (ML2487/8A) or R82 (ML2495/6A and ML2487/8B) so the DVM reads the value
calculated in Step 5,±2mV.
9. Reset the unit by pressing the front panel keys as follows:
Preset | Sel
10. Record results in Section 4-5: DC Reference Calibration of Appendix A, “Test Records”.
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