RKI Instruments 65-2380SS User manual

RKI Instruments, Inc.
www.rkiinstruments.com
65-2380SS
Molecular Property Spectrometer
Combustible Gas Detector
Operator’s Manual
Part Number: 71-0620
Revision: 0
Released: 1/23/23
TM

2• 65-2380SS Molecular Property Spectrometer
WARNING
Read and understand this instruction manual before operating
transmitter. Improper use of the transmitter could result in bodily
harm or death.
Periodic calibration and maintenance of the transmitter is essential for
proper operation and correct readings. Please calibrate and maintain
this transmitter regularly! Frequency of calibration depends upon the
type of use you have and the sensor types. For most applications,
typical calibration frequencies are between 6 and 12 months but can
be more often or less often based on your usage.

65-2380SS Molecular Property Spectrometer • 3
Product Warranty
RKI Instruments, Inc. warrants gas alarm equipment sold by us to be free from defects in
materials, workmanship, and performance for a period of one year from date of shipment from
RKI Instruments, Inc. Any parts found defective within that period will be repaired or replaced, at
our option, free of charge. This warranty does not apply to those items which by their nature are
subject to deterioration or consumption in normal service, and which must be cleaned, repaired, or
replaced on a routine basis. Examples of such items are:
• Absorbent cartridges
• Pump diaphragms and valves
•Fuses
•Batteries
• Filter elements
Warranty is voided by abuse including mechanical damage, alteration, rough handling, or repair
procedures not in accordance with the operator’s manual. This warranty indicates the full extent
of our liability, and we are not responsible for removal or replacement costs, local repair costs,
transportation costs, or contingent expenses incurred without our prior approval.
THIS WARRANTY IS EXPRESSLY IN LIEU OF ANY AND ALL OTHER WARRANTIES AND
REPRESENTATIONS, EXPRESSED OR IMPLIED, AND ALL OTHER OBLIGATIONS OR
LIABILITIES ON THE PART OF RKI INSTRUMENTS, INC. INCLUDING BUT NOT LIMITED TO,
THE WARRANTY OF MERCHANTABILITY OR FITNESS FOR APARTI CULAR PURPOSE. INNO
EVENT SHALL RKI INSTRUMENTS, INC. BE LIABLE FOR INDIRECT, INCIDENTAL, OR
CONSEQUENTIAL LOSS OR DAMAGE OF ANY KIND CONNECTED WITH THE USE OF ITS
PRODUCTS OR FAILURE OF ITS PRODUCTS TO FUNCTION OR OPERATE PROPERLY.
This warranty covers instruments and parts sold to users by authorized distributors, dealers, and
representatives as appointed by RKI Instruments, Inc.
We do not assume indemnification for any accident or damage caused by the operation of this gas
monitor, and our warranty is limited to the replacement of parts or our complete goods.

4• 65-2380SS Molecular Property Spectrometer
Table of Contents
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
MPS Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Junction Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Amplifier. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Mounting the Combustible Gas Transmitter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Wiring the Combustible Gas Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Startup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Introducing Incoming Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Setting the Zero Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Preventive Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Replacing the MPS LEL Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Calibration Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Preparing for Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Setting the Zero Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Setting the Response Reading. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Returning to Normal Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Overview • 5
Overview
This manual describes the 65-2380SS MPS combustible gas detector. This manual also describes
how to install, start up, maintain, and calibrate the detector when used with a gas monitoring
controller. A parts list at the end of this manual lists replacement parts and accessories for the
combustible gas detector.
Specifications
Table 1 specifies the detection ranges and accuracy for each target gas the MPS sensor can detect.
Table 1: Detection Ranges and Accuracy
Target Gas Formula Detection Range Accuracy
at 50% LEL
Butane C4H10 0 - 100% LEL ± 5% LEL
Ethane C2H60 - 100% LEL ± 5% LEL
Hydrogen H20 - 100% LEL ± 5% LEL
Isobutane HC(CH3)30 - 100% LEL ± 5% LEL
Isobutylene C4H80 - 100% LEL ± 5% LEL
Isopropanol C3H8O 0 - 100% LEL ± 10% LEL
Methane CH40 - 100% LEL ± 3% LEL
Methyl Ethyl Ketone C4H8O 0 - 100% LEL ± 5% LEL
Octane C8H18 0 - 100% LEL ± 5% LEL
Pentane C5H12 0 - 100% LEL ± 5% LEL
Propane C3H80 - 100% LEL ± 6% LEL
Propylene C3H60 - 100% LEL ± 5% LEL
Toluene C7H80 - 100% LEL ± 12% LEL
Xylene C8H10 0 - 100% LEL ± 12% LEL
NOTE: The MPS sensor will respond to other combustible gases, but the accuracy has
only been determined for these 14 gases.

6• Applications
WARNING: When using the 65-2380SS, you must follow the instructions and warnings in
this manual to assure proper and safe operation of the 65-2380SS and to
minimize the risk of personal injury. Be sure to maintain and periodically
calibrate the 65-2380SS as described in this manual.
Applications
The MPS combustible detector is most effective in the following applications:
• High concentrations of hydrogen sulfide (H2S) or silicones present where sensor
poisoning is a common problem
• High-humidity environments where catalytic or IR sensors may not hold up
• Environments more likely to have mixtures of hydrocarbons present
Table 2: Specifications
Area Classification Explosion-proof for Class I, Groups B, C, and D
Operating Temperature
Range
-20ºC to +50ºC (-4ºF to +122ºF)
Humidity Range 0 - 100% RH (non-condensing)
Pressure Range 80 - 120 kPa
Sampling Method Diffusion
Response Time T90 in 25 seconds
Dead Bands
•Methane(CH
4): 3% LEL
• All other gases: 5% LEL
NOTE: If the connected controller’s dead band setting is 2% LEL for
an MPS channel, a reading will not be displayed until it has exceeded
the MPS sensor's internal dead band.

Description • 7
Description
The 65-2380SS combustible gas transmitter utilizes a Molecular Property Spectrometer (MPS)
sensor. The MPS sensor is immune to poisons, can be used in high humidity, and does not require
calibration as often as catalytic combustible sensors. It also responds accurately to 14 different
combustible gases.
This section describes the components of the combustible gas transmitter. The transmitter is a 4 -
20 mA type detector head. It consists of the combustible gas detector, amplifier, and junction box.
Figure 1: Component Locations
R G
LEL PWR / SIG
WBS
Amplifier
J-Box
MPS LEL
Detector
ZERO
SPAN
Sensor
Current
mA

8• Description
MPS Detector
The MPS LEL detector is made up of the MPS combustible gas LEL detector housed and
encapsulated in a pipe nipple. The pipe nipple has 3/4 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
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. Use the leads when connecting the detector to the terminal block in the
junction box.
Junction Box
The stainless steel, corrosion-resistant junction box allows you to install the detector at a
mounting site that is remote from a controller, and it protects the amplifier and wiring connections
made to the amplifier. An O-ring seals the interface between the junction box cover and the
junction box base. A locking set screw on the junction box cover allows you to secure the junction
box cover and prevent it from being removed.
Use the top 3/4 NPT conduit hub to connect wiring from the amplifier to the controller. Use the
cover on the front of the junction box to access the interior of the junction box. The detector and
amplifier are factory installed in the junction box.
Amplifier
The amplifier converts the electrical output from the detector to a 4 - 20 mA signal that
corresponds to the detection range and transmits the signal to a gas monitoring controller. A foam
gasket that orients the amplifier and keeps it from rotating is installed on the bottom of the
amplifier. A label on the amplifier indicates the detector drive current. The amplifier includes the
detector terminal strip, controller terminal strip, span pot, zero pot, and test points (see Figure 2).
Figure 2: Amplifier Component Location
Black - Test Point
LEL PWR / SIG
WB
GS
R
ZERO
SPAN
Sensor
Current
mA
Factory Adjust Pot
Zero Pot
Span Pot
Amplifier
Mounting Screw
Detector Terminal Strip
Controller Terminal Strip
Red + Test Point

Description • 9
Controller Terminal Strip
The controller terminal strip is a three position plug-in style terminal strip located near the top of
the amplifier. Use the controller terminal strip to wire the combustible gas transmitter to a
controller.
Detector Terminal Strip
The detector terminal strip is a four position plug-in style terminal strip located below the
controller terminal strip. Use the detector terminal strip to connect the MPS LEL detector to the
amplifier.
NOTE: The MPS LEL detector is factory-wired to the detector terminal strip. See “Wiring the
Combustible Gas Detector to a Controller” on page 11 for all wiring procedures related
to the transmitter.
Zero Pot
The zero pot is located in the upper left corner of the amplifier (see Figure 2). Use a small flat
blade screwdriver to turn the zero pot’s adjustment screw and adjust the amplifier’s zero (fresh
air) output during the start-up and calibration procedures. Turn the adjustment screw clockwise to
increase the zero output and counterclockwise to decrease the zero output.
Span Pot
The span pot is located to the right of the zero pot (see Figure 2). Use a small flat blade
screwdriver to turn the span pot’s adjustment screw and adjust the amplifier’s gas response output
during the calibration procedure. Turn the adjustment screw clockwise to increase the gas
response and counterclockwise to decrease the gas response.
CAUTION: The amplifier includes two additional potentiometers. They are factory-set. Do not
adjust them.
Test Points
The test points are on the left side of the amplifier (see Figure 2). The test points produce a 100
mV to 500 mV output that corresponds to the transmitter’s 4 to 20 mA output. Use the test points
and a voltmeter to measure the amplifier’s output during the start-up and calibration procedures.
The black test point in the lower left corner is the negative (-) test point and the red test point
below the zero pot is the positive (+) test point.

10 • Installation
Installation
This section describes procedures to mount the combustible gas transmitter in the monitoring
environment and wire the transmitter to a controller.
Mounting the Combustible Gas Transmitter
1. Select a mounting site that is representative of the monitoring environment. Consider the
following when you select the mounting site.
• Select a site where the transmitter is not likely to be bumped or disturbed. Make sure there
is sufficient room to perform start-up, maintenance, and calibration procedures.
• Select a site where the target gas is likely to be found first. For lighter gases, mount the
detector near the ceiling; for heavier gases, mount the detector near the floor.
Figure 3: Mounting the Combustible Gas Transmitter
2. At the monitoring site you select, hang or mount the junction box with the detector facing
down (see Figure 3).
.20 Dia. x
.45 Slot, 2X
3/4 NPT
Female,
2X
2.40
MPS LEL
Detector
J-Box
3.66
3.15 3.34
1.10
6.80 max

Installation • 11
Wiring the Combustible Gas Detector to a Controller
WARNING: Always verify that the power to the controller is off before you make wiring
connections.
1. Turn off the controller.
2. Turn off or unplug power to the controller.
3. Remove the junction box cover.
4. The detector leads are factory wired. Verify that the detector leads are wired to the amplifier’s
detector terminal strip as shown in Figure 11.
5. To gain access to a plug-in terminal strip for wiring, pull it out of its socket by grasping the
terminal strip and pulling. The detector strip is keyed so that the controller and detector
terminal strips cannot be reversed inadvertently.
6. Guide a three-conductor, shielded cable, or three wires in conduit through the top conduit hub
of the junction box.
7. Pull out the controller terminal strip, and connect the three wires to the terminal strip as
follows (see Figure 11).
• Connect the positive wire to the PWR/SIG “+” terminal.
• Connect the signal wire to the PWR/SIG “S” terminal.
• Connect the negative wire to the PWR/SIG “-” terminal.
CAUTION: If shielded cable is used, leave the cable shield’s drain wire
disconnected and insulated at the transmitter. You will connect the
opposite end of the cable’s drain wire to the controller’s chassis (earth)
ground.
8. Reinstall the controller terminal strip into its socket.
9. Secure the junction box cover to the junction box.
10. Route the cable or wires leading from the combustible gas transmitter through one of the
conduit hubs at the controller housing.
CAUTION: Do not route power and transmitter wiring through the same controller
conduit hub. The power cable may disrupt the transmission of the
transmitter signal to the
controller.

12 • Installation
11. Connect the wires to the applicable detector/transmitter terminal strip at the controller as
shown in Figure 11.
12. If shielded cable is used, connect the cable’s drain wire to an available chassis (earth) ground
at the controller. RKI controllers typically have a ground stud that can be used to ground the
cable’s drain wire.
+ 24 VDC
Black
White
Red
Green
Cable Shield
S
PWR/ SIG
W GR B
LE L
Amplifier (Transmitter)
Detector Wires
MPS LEL
Detector
J-Box
Controller or
Recording Device
- (DC Ground)
4 - 20 mA In (S)
Figure 4: Wiring the Combustible Gas Transmitter to a Controller

Start Up • 13
Start Up
This section describes procedures to start up the combustible gas transmitter and place the
transmitter into normal operation.
NOTE: Ensure the detector starts up in the background gas it will operate in (e.g. fresh air or
N2).
Introducing Incoming Power
1. Complete the installation procedures described earlier in this manual.
2. Verify that the power wiring to the controller is correct and secure. Refer to the controller
operator’s manual.
3. Turn on or plug in power to the controller, then turn on the controller.
4. Verify that the controller is on and operating properly. Refer to the controller operator’s
manual.
5. Allow the combustible detector to warm up for at least 2 minutes before proceeding to the
next section, “Setting the Zero Reading”.
CAUTION: Do not expose the sensor to combustible gas during the 2-minute
warmup period. Exposing the sensor to gas during this period will
result in a failure condition.
Setting the Zero Reading
WARNING: Do not remove the junction box cover while the circuits are energized unless the
area is determined to be non-hazardous. Keep the junction box cover tightly
closed during operation.
WARNING: This manual assumes the MPS sensor is operating in a background of fresh air.
If the MPS sensor is not operating in a fresh air background (e.g. a monitoring
background of nitrogen or argon), consult RKI Instruments Inc. before
calibrating the sensor.
The procedure below describes setting the detector’s zero reading using a calibration kit that
includes a calibration cup, calibration gas, sample tubing, and a fixed flow regulator with an on/
off knob. RKI Instruments, Inc. recommends using a 0.5 LPM (liters per minute) fixed flow
regulator.
1. Unscrew and remove the junction box cover from the junction box.
2. Set a voltmeter to measure in the millivolt (mV) range.

14 • Maintenance
3. Plug the voltmeter leads into the test points on the amplifier. Plug the positive lead into the red
(+) test point; plug the negative lead into the black (-) test point.
4. Screw the calibration cup onto the bottom of the MPS LEL detector.
5. Screw the zero air cylinder onto the regulator.
NOTE: If you can verify that the combustible gas transmitter is operating in a fresh
air environment (environment with a normal oxygen content of 20.9% and
free of combustible and toxic gases), you do not need to apply zero air before
adjusting the zero reading.
6. Use the calibration kit sample tubing to connect the regulator to the calibration cup.
7. Turn the regulator’s on/off knob counterclockwise to open it.
8. Allow the gas to flow for 1 minute.
9. Verify a voltmeter reading of 100 mV (±2 mV).
10. If necessary, use a small flat-blade screwdriver to adjust the zero pot until the voltmeter
reading is 100 mV (±2 mV).
11. Turn the regulator’s on/off knob clockwise to close it.
12. Unscrew the calibration cup from the detector.
13. Unscrew the regulator from the zero air calibration cylinder. For convenience, leave the
sample tubing connected to the regulator and the calibration cup.
14. Store the components of the calibration kit in a safe and convenient place.
15. Remove the voltmeter leads from the test points.
16. Secure the junction box cover to the junction box.
Maintenance
This section describes maintenance procedures. It includes preventive maintenance,
troubleshooting, and component replacement procedures.
Preventive Maintenance
This section describes a preventive maintenance schedule to ensure the optimum performance of
the combustible gas transmitter. It includes daily and biannual procedures.
Daily
Verify a display reading of 0% LEL at the controller. Investigate significant changes in the display
reading.
Biannually
Calibrate the combustible gas transmitter as described in “Calibration” on page 18 of this manual.

Maintenance • 15
Troubleshooting
The troubleshooting guide describes symptoms, probable causes, and recommended action for
problems you may encounter with the combustible gas transmitter.
NOTE: This troubleshooting guide describes transmitter problems only. See the controller
operator’s manual for problems you may encounter with the controller.
Table 3: Troubleshooting the Combustible Gas Transmitter
Condition Symptom(s) Probable Causes Recommended Action
Fail Condition • Controller indicates
a fail condition.
• The transmitter
wiring is
disconnected or
misconnected.
• The transmitter’s
zero reading is low
enough to cause a
fail condition.
• The detector was
exposed to gas
during its 2 minute
warmup period.
• The transmitter is
malfunctioning.
1. Verify that the transmitter wiring
is correct and secure.
2. Calibrate the transmitter.
3. Restart the controller and ensure
that the detector’s environment is
free of combustible gas during
the warmup period.*
4. If the fail condition continues,
replace the detector.
5. If the fail condition continues,
contact RKI for further
instruction.
Slow or No
Response/Dif-
ficult or
Unable to Cali-
brate
• Unable to
accurately set the
zero or response
reading during
calibration.
•Transmitter
requires frequent
calibration.
NOTE: Under
“normal”
circumstances, the
transmitter requires
calibration once
every 6 months.
NOTE: Some
applications may
require a more
frequent calibration
schedule.
• The calibration
cylinder is low, out-
dated, or defective.
• The calibration gas
flow rate is too low.
• The calibration gas is
not an appropriate
concentration.
• The transmitter is
malfunctioning.
1. Verify that the calibration
cylinder contains an adequate
supply of a fresh test sample.
2. Verify that the regulator used for
calibration is a 0.5 LPM
regulator.
3. Verify that the calibration gas
concentration is appropriate for
the transmitter. The concentration
should be in the detection range,
preferably about half of the
detection range.
4. If the calibration/response
difficulties continue, replace the
detector.
5. If the calibration/response
difficulties continue, contact RKI
for further instruction.
* If a fresh air environment cannot be guaranteed, apply zero air during the warmup period.

16 • Maintenance
Replacing the MPS LEL Detector
1. Turn off the controller.
2. Turn off or unplug power to the controller.
3. Remove the junction box cover.
4. Remove the detector terminal strip from its socket.
5. Disconnect the detector leads from the detector terminal strip. Note the position of the color-
coded leads as you remove them.
6. Unscrew the detector from the junction box.
7. Guide the detector leads of the replacement detector through the bottom conduit hub of the
junction box, then screw the mounting threads of the detector into the conduit hub. If
necessary for environmental conditions, apply thread sealant or Teflon tape to the hub and/or
detector threads to seal them.
8. Connect the detector leads to the detector terminal strip as shown in Table 4 below and
Figure 11 on page 12 of this manual.
9. Reinstall the detector terminal strip into its socket.
10. Reinstall the junction box cover.
11. Turn on or plug in power to the controller.
12. Turn on the controller and place it into normal operation.
CAUTION: Allow the replacement detector to warm up for at least 2 minutes before
you continue with the next step.
13. Calibrate the transmitter as described in “Calibration” on page 18 of this manual.
Table 4: Reconnecting the Combustible Gas Detector to the Amplifier
Detector Lead Detector Terminal Strip
Red LEL “R”
White LEL “W”
Green LEL “G”
Black LEL “B”

Maintenance • 17
Replacing the Amplifier
1. Turn off the controller.
2. Turn off or unplug power to the controller.
3. Remove the junction box cover.
4. Unplug the detector terminal strip and controller terminal strip from their sockets. You may
leave the wires connected to the terminal strips.
5. Unscrew and remove the screw with the flat and lock washers that secures the amplifier to the
junction box.
6. Remove the old amplifier.
7. Place the new amplifier in the same position as the old amplifier. A foam gasket that orients
the amplifier and keeps it from rotating is installed on the bottom of the amplifier. Make sure
the amplifier is seated flat in the junction box.
8. Install the new amplifier into the junction box with the screw, lock washer, and flat washer
you removed in Step 5 above.
9. Install the detector and controller terminals strips into their sockets on the new amplifier as
shown in Figure 11 on page 12 of this manual. If controller leads or detector leads were
removed during this procedure, refer to Table 5 and Table 6.
Table 5: Reconnecting the Amplifier to the Controller
Amplifier
Controller
Terminal Strip
Controller
Transmitter Terminal
Strip (typical)
PWR/SIG “-” - (DC -)
PWR/SIG “S” S (4 - 20 mA In)
PWR/SIG “+” + 24V
Table 6: Reconnecting the LEL Detector to the Amplifier
Amplifier Detector
Terminal Strip Detector Lead
DETECTOR “R” RED
DETECTOR “W” WHT
DETECTOR “G” GREEN
DETECTOR “B” BLK

18 • Calibration Frequency
NOTE: When a transmitter is first powered up with a new amplifier, the initial
output may be either high or below zero depending on the setting of the zero
pot. Be sure to make arrangements so that this does not cause unwanted
alarms.
10. Turn on power to the controller.
11. Turn on the controller and place it into normal operation.
12. Allow the transmitter to warm-up for 5 minutes.
13. Calibrate the transmitter as described in “Calibration” on page 18 of this manual.
Calibration Frequency
Although there is no particular calibration frequency that is correct for all applications, a
calibration frequency of every 6 months is adequate for most MPS combustible gas transmitter
applications. Unless experience in a particular application dictates otherwise, RKI Instruments,
Inc. recommends a calibration frequency of every 6 months.
If an application is not very demanding, for example detection in a clean, temperature controlled
environment where calibration adjustments are minimal at calibration, then a calibration
frequency of every 9 to 12 months is adequate.
If an application is very demanding, for example if the environment is not well controlled, then
more frequent calibration than every 6 months may be necessary.
Calibration
This section describes how to calibrate the combustible gas transmitter. It includes procedures to
prepare for calibration, set the zero reading, set the response reading, and return to normal
operation.
WARNING: The controller is not an active gas monitoring device during the calibration
procedure.
NOTE: During calibration, the detector must be calibrated with a cylinder of methane in a
background of real air containing argon and CO2. Only use the RKI-provided
calibration cylinder 81-9070RK-03.
Materials
The following items are required for detector calibration:
•aCH
4calibration cylinder (in a background of real air which contains argon and CO2)
• a 0.5 LPM fixed flow regulator with an on/off knob
• a calibration cup for the detector

Calibration • 19
• a short piece of sample tubing to connect the regulator to the calibration cup
• a voltmeter
• a zero air cylinder (required for fresh air environments where there may be a temporary
presence of combustible or toxic gas)
Preparing for Calibration
1. Unscrew and remove the junction box cover.
2. Set a voltmeter to measure in the millivolt (mV) range.
3. Plug the voltmeter leads into the test points on the amplifier. Plug the positive lead into the red
(+) test point; plug the negative lead into the black (-) test point.
4. Use the following formula to determine the correct test points output for the calibrating
sample.
Output (mV) = (calibrating sample/fullscale) X 400 + 100
For example, with a calibrating sample of 50% LEL and a fullscale setting of
100% LEL, the correct output is 300 mV.
300(mV) = (50/100) X 400 +100
5. Screw the calibration cup onto the detector housing.
6. Use the sample tubing to connect the regulator to the calibration cup.
7. Place the controller into its calibration mode or disable external alarms.
NOTE: Calibrating the combustible gas transmitter may cause alarms. Be sure to put
the controller into its calibration mode or disable external alarms before
continuing.
8. Allow the combustible detector to warm up for at least 2 minutes before proceeding to the
next section, “Setting the Zero Reading”.
CAUTION: Do not expose the sensor to combustible gas during the 2-minute
warmup period. Exposing the sensor to gas during this period will
result in a failure condition.

20 • Calibration
Setting the Zero Reading
WARNING: This manual assumes the MPS sensor is operating in a background of fresh air.
If the MPS sensor is not operating in a fresh air background (e.g. a monitoring
background of nitrogen or argon), consult RKI Instruments Inc. before
calibrating the sensor.
WARNING: Do not remove the junction box cover while the circuits are energized unless the
area is determined to be non-hazardous. Keep the junction box cover tightly
closed during operation.
1. Screw the regulator into the zero air calibration cylinder.
NOTE: If you can verify that the combustible gas transmitter is operating in a fresh
air environment (environment with a normal oxygen content of 20.9% and
free of combustible and toxic gases), you do not need to apply zero air before
adjusting the zero reading.
2. Use the calibration kit sample tubing to connect the regulator to the calibration cup.
3. Turn the regulator’s on/off knob counterclockwise to open the regulator.
4. Allow the gas to flow for one minute and verify a reading of 100 mV (±2 mV). If necessary,
use the zero pot on the amplifier to adjust the reading to 100 mV (±2 mV).
5. Turn the regulator’s on/off knob clockwise to close the regulator.
6. Unscrew the regulator from the zero air calibration cylinder.
7. Leave the sample tubing connected to the regulator and the calibration cup.
Setting the Response Reading
1. When the directions call for exposing the detector to gas, screw the regulator into the
methane in real air cylinder provided by RKI Instruments Inc.
2. Turn the regulator’s on/off knob counterclockwise to open the regulator.
3. Allow the calibration gas to flow for one minute and verify that the reading matches the
response reading (±2 mV) you determined earlier. If necessary, use the span pot on the
amplifier to adjust the reading to match the correct response reading.
4. Turn the regulator’s on/off knob clockwise to close the regulator.
5. Unscrew the regulator from the calibration cylinder.