RKI Instruments 65-2390RK - Manual (Page 6)

2 • 65-2390RK Combustible Gas Transmitter
Description
The 65-2390RK combustible gas transmitter has two versions, the 65-2390RK-CH4 which
is calibrated to methane and the 65-2390RK-HC which is calibrated to propane. The
transmitter utilizes an infrared type of detector which has some advantages over a
catalytic type of combustible detector. The infrared detector will generally have a longer
service life than a catalytic detector, it will require calibration less often, and it can detect
combustible gas even if there is no oxygen in the sample which allows detection of
combustible gas in an inert atmosphere.
This section describes the components of the combustible gas transmitter. The transmitter
is a 4 - 20 mA type detector head. It consists of the infrared LEL detector, amplifier, and
junction box.
Figure 1: Combustible Gas Transmitter Component Location
Infrared LEL Detector
The infrared LEL detector is made up of a miniature infrared combustible gas LEL
detector housed and encapsulated in a pipe nipple. The pipe nipple has 3/4 inch NPT
threads on each end and a 1 1/4 inch hex that allows removal or installation of the
detector with a wrench. A porous flame arrestor that is coated with a hydrophobic film
that repels liquids is on one end of the detector and allows sample gas to enter the
detector. Four color coded leads, red, white, green, and black, extend from the other end of
the detector. The leads allow you to connect the detector to the amplifier.
To distinguish the propane detector from the methane detector (in case the replacement
sensor label that is applied to one of the leads is lost), a short length of red shrink tubing is
Interconnect Terminal Strip
Factory Set Pots
J-Box
Amplifier
Test Points
100-500 mV Range
Jumper Pins for
Factory Use Only
Span Pot
Zero Pot
IR LEL Detector
TP +
GND
24V
4/20
RED
WHT
GRN
BL K
PO
WE
R
/S
IG
SE
N
S
O
R
TP -