DTM900 and DTM920 Adjustment Procedures
Handheld and Benchtop Instruments Basic Service
15
DTM920 Adjustment Procedure
This section describes how to adjust the DTM920 thermometer. To properly
adjust the thermometer, perform the following steps in sequential order. Figure 3
shows the location of the test and adjustment points.
1. Open the thermometer. (See page 12 for instructions.)
2. Solder a jumper across R25.
3. Turn on the thermometer and allow it to warm up for at least 30 minutes.
Use the following procedure to perform a 2000 mV calibration.
1. Press T2 once to access the T2 mode.
2. Install a jumper across the test points marked JP1.
3. Connect the DC voltage source to the T1 probe connector. The composition
of both lead wires should be identical.
4. Set the DC voltage source output to +2000.0 mV ±0.01%.
5. Adjust VR2 until the display shows 2000.0_. (The first digit of the
temperature appears at the upper right-hand corner of the display.)
6. Disconnect the DC voltage source.
7. Remove the R25 jumper. (Do not remove the JP1 jumper.)
Use the following procedure to perform a gain calibration.
1. Press _C/_F until ‘‘1L” appears in the upper left-hand corner of the display.
2. Set the DC voltage source output to +50.000 mV ±0.01%.
3. Reconnect the DC voltage source to the T1 probe connector.
4. Adjust VR3 until the display shows 000.0_. (The first digit of the tempera-
ture appears at the upper right-hand corner of the display.)
5. Disconnect the DC voltage source.
6. Remove the JP1 jumper.
2000 mV Calibration
Gain Calibration
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