
www.vaisala.com
FIELD CHECK OF CARBON DIOXIDE
TRANSMITTERS
The field check adapter for Vaisala CARBOCAP¨Carbon
Dioxide Probes Series GMP220 can be used as
-a chamber for feeding in reference gas in a field checking
of the probes
-a chamber for pump aspirated sampling system.
Note that a field comparison can only check the performance of
the transmitter. For accurate calibration and adjustment, the
probe or transmitter should be returned to Vaisala Service
Centre.
Field Check Equipment
•Accurate reference gas (Basically any concentration within
the measurement range will do. If available, a good choice
is one close to the normal measurement concentration.)
•A pressure regulator for reducing the pressure of the
calibration gas
•A flow meter to adjust the gas flow
•Tubing with 3mm (1/8") inner diameter (for example
neoprene tubing, part no. 18229. (Teflon tube NOT
recommended).
•The field check adapter (part no. 26150 GM)
Field Check Instructions for the GMT220-series
1. Attach the adapter to the probe of your GMT220 series
transmitter. The adapter fits both the probe sizes available
(GMP221 and GMP222) and can be attached to a probe on a
transmitter as well as one attached to a cable. Push the adapter
up the probe. Connect tubing to the bottom port of the adapter.
2. Connect the adapter with the tubing to the flow meter, the
pressure regulator, and further to the reference gas bottle. The
other port of the adapter is left open for gas outflow.
3. Let the reference gas flow through the pressure regulator and
the flow meter to the adapter. The recommended flow rate is 0.6
l/min. Let the transmitter stabilize for 5 minutes.
4. Check the reading on the display, or if the transmitter has no
display, from the analog output. If the difference between the
reading and the reference gas concentration after pressure and
temperature correction is more than the accuracy and long-term
stability specifications allow, detach the probe and send it to
Vaisala for adjustment.
Note when installing the probe
-The probe should be pushed into the adapter deep enough, so
that none of the diffusion holes will be outside the adapter
chamber.
-Also the excess space inside the chamber should be
minimized by pushing the probe well inside the chamber
(this is especially important if using the field check adapter
with inadequate gas flows of below 0.4 l/min)
Important note for the GMP221 !
When using the shorter probe (GMP221) with the Field
Check Adapter, the adapter must be inserted on the probe
so that the o-ring inside the adapter is not on the sticker of
the probe (see Figure). If the adapter is placed on the
sticker, the seam between the probe and the adapter will
let the gas leak from the chamber.
The Field Check Adapter and a GMP220 Series probe.
VAISALA SERVICE CENTERS
flow meter
GMT220/ GMM220 series
transmitter
CO2
pressure regulator
NORTH AMERICAN SERVICE CENTER
Vaisala Inc., 100 Commerce Way, Woburn,
MA 01801-1068, USA.
Phone: +1 781 933 4500, Fax +1 781 933 8029
Email: us-customersupport@vaisala.com
EUROPEAN SERVICE CENTER
Vaisala Instruments Service, Vanha Nurmijärventie 21
FIN-01670 Vantaa, FINLAND.
Phone: +358 9 8949 2758, Fax +358 9 8949 2295
ASIAN SERVICE CENTER
Vaisala KK, 42 Kagurazaka 6-Chome, Shinjuku-Ku,
Tokyo 162-0825, JAPAN.
Phone: +81 3 3266 9611, Fax +81 3 3266 9610
E-mail:aftersales.asia@vaisala.com
www.vaisala.com
O-ring inside the adapter shall
not be on the sticker of the
probe !