Vaisala GM70 - Manual (Page 45)

Chapter 9 ______________________________ Field Checking of Fixed Transmitters
VAISALA __________________________________________________________ 45
Field Checking of the Vaisala GMD/W20
Series Transmitters (Pump Aspirated
Sampling)
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 the GM70's display simultaneously when using a connecting
cable GMA70 (see section Accessories on page 65).
1. Connect the GMA70 cable between the MI70 indicator's connector
port and the
SERIAL COM pins in the motherboard of the GMD/W20
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 the GM70PUMP.
3. Connect the other end of the tube:
- GMD20: to the sampling port located in the middle of the
GMD20's motherboard (protected with a yellow cap).
- GMW20: to the sampling port located on the GMW20's
motherboard (protected with a yellow cap).
4. Insert the calibrated GMP220 probe to the measuring chamber of
the GM70PUMP.
5. Turn on the MI70 indicator and the GM70PUMP.
6. Compare the readings. In case there is need for an adjustment, send
the transmitter to a Vaisala Service Center to be adjusted or make
an adjustment by using a calibration software kit (19222GM).
NOTE Please do not breathe towards the transmitter when checking the
readings.