ENMET EX-5000 - Manual (Page 10)

ENMET Corporation MOS S/T
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3.2 Initial Calibration
The S/T has been precalibrated at the factory before shipment, and initial field calibration should result in only fine-
tuning of the circuit. Wait at least 24 hours after initially supplying power to the S/T before initial calibration. If
purge option is available, see purge section 3.3.
It is important to zero the S/T before applying the calibration gas. If the display is not reading at or very close to zero,
apply clean air to the sensor.
If sensor does not zero:
§ Declassify the area before opening the enclosure.
§ Apply clean air (20.9% O2 78.1% N2) to the sensor and adjust the zero manual potentiometer to provide a reading
of zero on the display. See the circuit board diagram figure 1a for the location of this potentiometer.
§ Then close the enclosure.
N
OTE : These potentiometers are accessible without removing the display plate.
3.3 Purge
When this option is present, activate before calibration. While activating the purge switch the yellow LED is lit to
indicate the purge switch is active. A sensor needs only 10 to 30 seconds of purge. After removal of magnet the
switch and heater voltage will return to their normal state. After purge, the sensor needs to stabilize for 30 minutes
before applying calibration gas.
3.4 Span Adjustment
Do Not Adjust the Span Potentiometer Without Calibration Gas Applied To The Sensor; if this is done, the S/T is
rendered uncalibrated and incorrect.
§ If your calibration kit is supplied with a humidifier, fill the humidifier bowl half way with clean tap water. See figure 7
§ Attach the calibration adapter to the cylinder of gas associated with the S/T. See figure 6
§ Attach the calibration cover over the sensor. See figure 6
§ Apply the calibration gas to the sensor typically 3 minutes.
§ Use the magnet to adjust the span potentiometer up or down, until the display reads the calibration gas value.
§ Remove the calibration gas.
Figure 6: Gas cylinder and Typical Calibration Adapter
Figure 7: Calibration Adapter with Humidifier
3.5 Calibration
Subsequent calibrations are performed without opening the enclosure by applying calibration gas and using the magnet
to set the span as described above.
Gas Cylinder
Calibration
Adapter
Calibration
Cover
Sensor
Sensor/Transmitter
Humidifier Bowl