Vaisala GMT220 - Manual (Page 29)

Chapter 5 ______________________________________________________________ Maintenance
VAISALA _______________________________________________________________________ 29
On-site Checking and Adjusting with
Reference Gas and GM70 Hand-Held
Meter
A probe to be checked can be flushed in a reference gas by using a field
check adapter (optional part, 26150GM). The procedure requires
pressurized gas bottle giving a flow rate of 0.4...1.0 l/min through the
adapter chamber. If an adjustment is needed, it can be carried out by a
user with a Vaisala's hand-held carbon dioxide meter GM70. Probes can
also be sent to Vaisala Service Centers (see sections Technical Support
on page 33 and Product Returns on page 33) to be calibrated.
Follow the instructions below to check the operation of a GMP220 series
probe.
1. Check the display reading of the GM70.
2. Turn off the GM70.
3. Detach the GM70's probe as follows:
- Loosen the plastic probe fastener by unscrewing it about 5
turns.
- Take a firm hold from the base of the probe and pull strongly
until the probe comes loose.
4. Detach the GMP220 probe from the transmitter base (open the
cover, loosen the tightening screw and pull the probe out).
5. Insert the GMP220 probe to the GM70 handle as deep as possible.
Turn the probe inside the handle until you feel that a step in the
probe connector snaps into the groove of the probe handle
connector and locks the probe.
6. Tighten the probe fastener.
7. Turn on the GM70.
8. Compare the readings of the GM70 and the transmitter probe to be
checked.
9. If there is need for an adjustment, please contact Vaisala Service
Center or adjust the probe according to the instructions in sections
Two-Point Adjustment Procedure on page 30 and One-Point
Adjustment Procedure on page 32.
To perform the adjustment, you need the following:
- GM70 diffusion handle
- One or two accurate reference gases according to which adjustment
you do
- Pressure regulator