Atm Calibration Mode - MKS HPS 937A Series Owner's Operation And Maintenance Manual

ATM Calibration Mode

Atmosphere calibration is provided for the Pirani, Convection Pirani and
thermocouple sensors. Please refer to the next section for calibration of the
Convection Pirani sensor.
To perform Factory Calbration
1 Turn the Function Select switch to ATM Calibration.
2 Set the Gauge Select switch to the desired channel.
Press the Factory Cal push-button to set the atmosphere value to the
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factory default.
If the sensor is still calibrated for zero by the user, the U remains visible.
Otherwise, the U indicator is not displayed.
To perform User Calibration
1 Vent the system to atmospheric pressure or back fill it with air/
nitrogen using a reference sensor to avoid overpressure. Allow sensor
to stabilize for at least 10 minutes.
Turn the Function Select switch to ATM Calibration .
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Set the Gauge Select to the channel to be calibrated.
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4 Press and release the User Cal push-button to save the current
sensor pressure as the new atmospheric value.
The pressure reading will be displayed as AA for a Pirani and H I for
a thermocouple sensor. The indicator U will appear next to the display
of the channel.
A considerable atmospheric calibration change may activate
or deactivate a sensor's set point and shift various pressure
output readings.
The Series 315 Pirani sensor exhibits slight convection characteristics near
atmosphere. Therefore, the best accuracy can be achieved above 30 Torr by
calibrating the sensor oriented vertically with the port facing down. The Pirani
and thermocouple sensors can be calibrated at any pressure between 600
and 1000 Torr.
The Series 937A Controller does not allow user calibration when the reading is
outside the appropriate range. OUT momentarily appears on the display if the
pressure is out of the allowable calibration range. In this case, the new
calibration value will not be accepted. If a previous user calibration value had
been stored, the value will be retained and the U remains visible.
A special calibration algorithm in the 937A allows independent
zero and atmosphere calibration adjustments for Pirani,
Convection Pirani and thermocouple sensors.
937A Multi-Sensor System
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