18 • 65-2340RK Toxic Gas Transmitter
are minimal at calibration, then a calibration frequency of every 6 months is adequate.
If an application is very demanding, for example if the environment is not well controlled or if
toxic gas is often present, then more frequent calibration than every 3 months may be
necessary.
Calibration
This section describes how to calibrate the toxic gas transmitter. It includes procedures to
prepare for calibration, set the zero (fresh air) reading, set the span (response) reading, and
return to normal operation. It describes calibration using a calibration kit that includes a
calibration cup, calibration gas, sample tubing, and a fixed flow regulator with an on/off knob.
The required sample flow rate and calibration cup depend on the transmitter being calibrated.
Table 3 below lists the required calibration cups and regulators for the various toxic gas
transmitters.
WARNING: RKI Instruments, Inc. recommends that you dedicate a regulator for use with
chlorine (Cl
2
) gas and that you do not use that dedicated regulator for any
other gases, particularly hydrogen sulfide (H
2
S).
WARNING: Not using the recommended calibration cup, sample flowrate, and specified
flow direction (for 81-1138RK calibration cup only) will result in an
inaccurate calibration. Make sure to use the calibration cup and sample flow
rate listed in Table 3 for your target gas when performing a calibration. Also
make sure to connect the sample tubing to the calibration cup port that results
in the specified flow direction for the 81-1138RK calibration cup.
Table 3: Required Calibration Cups and Flow Rates
Transmitter Type
Required
Calibration Cup
Required Regulator/
Flowrate for Calibration
Gas
Flow Direction
Specified on
Calibration Cup
Arsine (AsH
3
)
81-1138RK
81-1051RK, 0.5 LPM (liters
per minute)
Yes
Chlorine (Cl
2
), 0 - 3.00 ppm
and 0 - 10.0 ppm
81-1138RK-CL2
81-1051RK, 0.5 LPM
No
Hydrogen Cyanide (HCN)
81-1138RK-HCN
81-1051RK, 0.5 LPM
Yes
Ammonia (NH
3
)
81-1138RK-NH3
81-1051RK-25, 0.25 LPM
No
Phosphine (PH
3
)
81-1138RK
81-1051RK, 0.5 LPM
Yes
Sulphur Dioxide (SO
2
)
81-1138RK
81-1051RK, 0.5 LPM
Yes
