RKI Instruments SDM-2009 - Manual (Page 25)

Connecting Calibration Gas • 21
Connecting Calibration Gas
The GAS fitting on the back of the docking station is designed to be used with a
calibration gas cylinder that is fitted with a demand flow regulator. The AIR fitting may
be used with a demand flow regulator and a cylinder of zero emissions air, but this is
not normally necessary since the docking station will generally be in a fresh air area.
The type of calibration gas cylinder used depends on the gas sensors installed in the
instrument being used with the calibration station. A 4-gas mix, LEL/Oxygen/CO/H
2
S,
is used if the instrument being used with the calibration station is a 4-gas unit. If the
instrument does not have an H
2
S channel, then a 3-gas mix, LEL/Oxygen/CO, is
used. Although a 4-gas cylinder will work for an instrument of any gas combination, if
you have multiple instruments with various gas combinations, you may want to keep
a 4-gas cylinder and a 3-gas cylinder to help preserve the charcoal filter on the CO
sensor in instruments without an H
2
S channel. Use Table 4 below as a guide in
determining which calibration gas cylinder is appropriate for your system. See “Spare
Parts List” on page 51 for a list of available cylinder part numbers.
To connect calibration gas to the SDM-2009, do the following:
1. If the area around the docking station is not considered a fresh air area (an
area free of combustible and toxic gases and of normal oxygen content,
20.9%) install a tube not longer than 10 feet on the filter attached to the AIR
fitting on the back of the docking station and route it to a fresh air area or
connect a cylinder of zero air with a demand flow regulator to the AIR fitting.
2. Install the demand flow regulator on the calibration gas cylinder(s).
3. Connect the demand flow regulator to the GAS fitting using the 3 foot length of
3/16 inch ID sample tubing provided with the docking station.
Table 4: Recommended Gas Cylinders
Typical Instrument Types
Recommended Calibration Gas
Cylinder(s)
LEL/Oxy/H
2
S/CO 4-gas mix with CH
4
/Oxy/H
2
S/CO
LEL/Oxy/CO 3-gas mix with CH
4
/Oxy/CO
LEL/Oxy/H
2
S 4-gas mix with CH
4
/Oxy/H
2
S/CO
LEL/Oxy 3-gas mix with LEL/Oxy/CO
Oxy/CO 3-gas mix with LEL/Oxy/CO
Oxy/H
2
S 4-gas mix with LEL/Oxy/H
2
S/CO