4-52 250cx Series Maternal/Fetal Monitor Revision C
2036947-001
Maintenance: Recorder Photosensor Calibration
Recorder Photosensor Calibration
Adjusting the Paper-Low Photosensor
1. Load paper in the recorder. Ensure that there are
no
black squares showing to
indicate a paper-low condition.
2. Press the Record button to turn on the recorder. Allow the paper to advance for
a few seconds in order to tension the paper.
3. Turn off the recorder.
4. Using a digital voltmeter, connect the positive lead to J9 (pin 4) on the Recorder
Board; connect the negative lead to J9 (pin 2).
5. Adjust R31 for a reading of +150 mVdc ± 2 mVdc on the digital voltmeter.
NOTE: If you open and then close the recorder door, the reading may vary 5–10
mV, due to the loss of tension in the paper. This is acceptable and you do
not need to re-adjust.
6. Open the door and verify that the reading on the digital voltmeter is greater than
+4.75 Vdc.
7. Re-load the paper so that black squares show on the surface (i.e., the last several
sheets of a pack).
8. Turn on the recorder.
9. The value on the digital voltmeter should go up and down as the paper surface
alternates between black and white. Verify that the maximum value is greater
than or equal to 2.0 Vdc.
10. Turn off the recorder.
Adjusting the Paper-Out Photosensor
1. Load paper in the recorder. Ensure that there are
no
black squares showing to
indicate a paper-low condition.
2. Press the Record button to turn on the recorder. Allow the paper to advance for
a few seconds in order to tension the paper.
3. Turn off the recorder.
4. Using a digital voltmeter, connect the positive lead to J9 (pin 3) on the Recorder
Board; connect the negative lead to J9 (pin 2).
5. Adjust R29 for a reading of +150 mVdc ± 2 mVdc on the digital voltmeter.
NOTE: If you open and then close the recorder door, the reading may vary 5–10
mV, due to the loss of tension in the paper. This is acceptable and you do
not need to re-adjust.
6. Open the door and verify that the reading on the digital voltmeter is greater than
+4.75 Vdc.
7. Turn off the recorder.
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