Field checking GMD20 series transmitters (pump-aspirated sampling) - GM70

GM70 User Guide

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User guide

The pump-aspirated system feeds the same gas sample to both the reference probe and the transmitter to be checked. Both readings can be seen on GM70's display simultaneously when using the connection cable GMA70 (optional accessory: for ordering information, see Spare parts and accessories).

To carry out a field check of GMD20 series transmitters:
  1. Connect the GMA70 cable between MI70 indicator's connector port and the SERIAL COM pins in the component board of the GMD20 series transmitter. If not using the GMA70 cable, check the transmitter reading from the transmitter output.
  2. Connect one end of the sampling tube to the gas inlet (marked with IN) of GM70PUMP.
  3. Connect the other end of the tube to the sampling port located in the middle of the GMD20 transmitter's component board (protected with a yellow cap).
  4. Insert the calibrated GMP220 series probe to the measuring chamber of GM70PUMP.
  5. Turn on the MI70 indicator and GM70PUMP.
  6. Compare the readings. In case there is need for an adjustment, send the transmitter to Vaisala to be adjusted. For contact information, see Technical support.

    Do not breathe towards the transmitter when checking the readings.