Field checking GMD20 series transmitters (diffusion sampling) - GM70

GM70 User Guide

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User guide

You can check the reading of a GMD20 series transmitter by using GM70 as a reference. Both readings can be seen on the GM70 display simultaneously when using the connection cable GMA70 (optional accessory: for ordering information, see Spare parts and accessories).

To carry out a field check:
  1. Connect the GMA70 cable to either of the GM70's connector ports located on the bottom of the indicator.
  2. Connect the other end of the GMA70 cable to the SERIAL COM pin connector of the transmitter component board.
  3. Switch on the MI70 indicator.
  4. Set the GM70 probe next to the transmitter to be checked. Ensure that the probes are located in the same conditions. Avoid breathing towards the probe as this alters the CO2 concentration and disturbs the readings.
  5. The reading of the transmitter is shown on the first or middle row of the display, depending on which connector is used. Value of connector I is shown on the upper row of the display. Value of connector II is on the lower row of the display. The difference of the readings is shown on the lowest row.
  6. Compare the readings. In case there is a need for an adjustment, send the transmitter to Vaisala to be adjusted. For contact information, see Technical support.