Fluke RUSKA 7252, User Manual

Page: 105 / 128

Maintenance
Sensor Photocell Zeroing
6
6-13
RPT — Instruments with the Barometric Reference Option
The barometric sensor is zeroed according to the following instructions.
1.
Verify that the Reference Port is open to atmosphere.
2. Enter the Calibration screen by selecting [MENU] MENU | CALIBRATE .
3. Select the Atmospheric Sensor by pressing the Sensor [ F6 ] key until the words
Atmospheric Sensor is displayed above the calibration coefficients.
4. To begin the zeroing process, press Zero . If the calibration access code is enabled,
enter it at the prompt. The Zeroing screen will appear.
Note
The next step requires the use of a properly calibrated standard. This
zeroing process does contribute directly to the overall accuracy of the
system, since the pressure applied to the sensor is a non-zero differential
pressure.
5. Enter the current barometric pressure. Press ENTER .
Sensor Photocell Zeroing
If the error message “Mechanical Zeroing Needed” is displayed, the sensor photocell
must be zeroed. The following steps describe this process. Press the MODE key to select
the desired channel.
WX
Warning
The Calibrator should only be opened by qualified
electrical/mechanical service technicians. Lethal voltages are
present and exposed in the power supply and display.
Note
The sensor MUST have zero differential between the Test port and
Reference port. For Gauge Calibrators, apply atmospheric pressure to the
Reference port. For Absolute Calibrators, apply a vacuum to the Reference
port (<200
μ
Hg.)
1. Remove the Calibrator’s top cover.
2. Locate and remove the plastic zeroing plug located in the side of the sensor oven
assembly.
3. Enter the Zeroing screen by selecting [MENU] MENU | CALIBRATE .
4. Select the Primary sensor by pressing the Sensor [ F6 ] key until the word Primary
is displayed above the calibration coefficients.
5. Select Zero . Do NOT press the Calibrate button.
6. Select the Mechanical Zero key.