RKI Instruments 65-2333 User manual

RKI Instruments, Inc.
www.rkiinstruments.com
65-2333
Hydrogen Cyanide Transmitter
Operator’s Manual
Part Number: 71-0265
Revision: P1
Released: 1/17/23

2• 65-2333 Hydrogen Cyanide Transmitter Operator’s Manual
WARNING
Read and understand this instruction manual before operating
detector. Improper use of the detector could result in bodily harm or
death.
Periodic calibration and maintenance of the detector is essential for
proper operation and correct readings. Please calibrate and maintain
this detector regularly! Frequency of calibration depends upon the
type of use you have and the sensor types. Typical calibration
frequencies for most applications are between 3 and 6 months, but can
be required more often or less often based on your usage.

65-2333 Hydrogen Cyanide Transmitter Operator’s Manual • 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
•Fuses
• Pump diaphragms and valves
•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 APARTICULAR 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• 65-2333 Hydrogen Cyanide Transmitter Operator’s Manual
Table of Contents
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
HCN Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Amplifier. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Junction Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Mounting the HCN Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Wiring the HCN Transmitter to a Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Startup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Introducing Incoming Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Setting the Zero Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Preventive Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Replacing Components of the HCN Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Calibration Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Preparing for Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Setting the Zero Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Setting the Response Reading. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Returning to Normal Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

65-2333 Hydrogen Cyanide Transmitter Operator’s Manual Overview • 5
Overview
This manual describes the 65-2333 explosion-proof hydrogen cyanide (HCN) transmitter. This
manual also describes how to install, start up, maintain, and calibrate the transmitter. A parts list
at the end of this manual lists replacement parts and accessories for the HCN transmitter.
Specifications
WARNING: Do not use this product in a manner not specified in this instruction manual.
Table 1 lists specifications for the HCN transmitter.
NOTE: The following symbol on the detector label is a caution to the user to refer to this
documentation for installation and operation instructions:
WARNING: When using the 65-2333, you must follow the instructions and warnings in this
manual to assure proper and safe operation of the 65-2333 and to minimize the
risk of personal injury. Be sure to maintain and periodically calibrate the 65-
2333 as described in this manual.
Table 1: Specifications
Target Gas Hydrogen cyanide (HCN)
Area Classification Explosion-proof for Class I, Groups B, C, and D
Temperature Code T6
Installation Category
Installation Category 1. Signal level, special equipment or
parts of equipment, telecommunication, electronic, etc., with
smaller transient overvoltages than Installation Category
(Overvoltage Category) II (ref. IEC 664).
Input Voltage 11 VDC - 30 VDC
Sampling Method Diffusion
Signal Output 4 to 20 mA
Detection Range 0 to 15.0 ppm (parts per million)
Accuracy ± 10% of reading or ± 5% of full scale (whichever is greater)
HCN Detector Signal
Output
0.3 mA at 0 ppm HCN nominal
2.5 mA at 15.0 ppm HCN nominal
Response Time 90% in 30 seconds
Operating Temperature -4°F to 104°F (-20°C to 40°C)
!

6• Description 65-2333 Hydrogen Cyanide Transmitter Operator’s Manual
Description
This section describes the components of the HCN transmitter. The transmitter consists of the
HCN detector, amplifier, and junction box.
Figure 1: HCN Transmitter Component Location
Amplifier
Controller Terminal Strip
SIG/PWR
HCN Detector
J-Box
Detector Terminal Strip
Factory Adjust Pot
Span Pot
Zero Pot
ZERO
SPAN
+ Test Point (Red)
- Test Point (Black)
S
TO XIC OXY

65-2333 Hydrogen Cyanide Transmitter Operator’s Manual Description • 7
HCN Detector
The HCN detector consists of the detector housing body, detector housing cap, cap gasket, rubber
boot, spacer, and the plug-in sensor.
Figure 2: HCN Detector Component Location
Detector Housing Body
The detector housing body protects the electronic components within the housing. Use the
mounting threads at the top of the housing to screw the HCN detector into the 3/4 NPT hub on the
bottom of the junction box. Two wires extend from the top of the detector housing body. Use these
wires to connect the HCN detector to the amplifier. One of the wires is red and one of the wires is
black.
The housing includes a four-socket pattern. This socket pattern accepts the sensor’s four pins to
secure the sensor within the detector housing. A pre-amplifier, located between the sockets and
two interconnect wires, conditions the sensor’s signal before the signal reaches the controller.
Housing Cap & Cap Gasket
The housing cap screws onto the detector housing. It retains the plug-in sensor and protects it
from damage. The housing cap also includes a flame arrestor which contains any sparks that may
occur within the detector and a flame arrestor guard which protects the flame arrestor from
damage. Unscrew the detector cap to access the plug-in sensor for maintenance or replacement. A
cap gasket seals the interface between the housing and cap.
Rubber Boot and Spacer
A rubber boot and spacer are installed between the detector housing cap and the sensor. They help
ensure that the detector remains plugged into the detector housing body.
Spacer
Rubber Boot
Flame
Arrestor
Guard
Detector
Housing Cap
Detector Housing Body
Cap Gasket
HCN Plug-in Sensor
VersaporR Membrane

8• Description 65-2333 Hydrogen Cyanide Transmitter Operator’s Manual
Plug-In HCN Sensor
The sensor is secured within the detector assembly by the housing cap. Through a series of
chemical and electrical reactions, the sensor produces an electrical output that corresponds to the
detection range of the transmitter. A VersaporR membrane is installed on the sensor face for
added protection from water and particulate contaminants.
Amplifier
The amplifier converts the electrical output from the sensor to a 4 to 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. The amplifier includes the controller terminal strip, detector terminal strip, zero pot,
span pot, and test points (Figure 1).
Controller Terminal Strip
The interconnect terminal strip is a two position plug-in style terminal strip located at the top edge
of the amplifier. Use the controller terminal strip to connect the amplifier to a controller.
Detector Terminal Strip
The detector terminal strip is a four-point plug-in style terminal strip near the bottom of the
amplifier. Use the detector terminal strip to connect the HCN detector to the amplifier.
NOTE: The HCN detector is factory-wired to the detector terminal strip. See “Installation” on
page 9 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 1). Use a small flat
blade screwdriver to turn the zero pot’s adjustment screw and adjust the amplifier’s zero (HCN
free) 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 1). Use a small flat blade
screwdriver to turn the span pot’s adjustment screw and adjust the amplifier’s response output
during the calibration procedure. Turn the adjustment screw clockwise to increase the output and
counterclockwise to decrease the output.
CAUTION: The third potentiometer is factory-set. Do not adjust it.
Test Points
The test points (red and black) are on the left side of the amplifier (see Figure 1). The test points
produce a 100mV 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.

65-2333 Hydrogen Cyanide Transmitter Operator’s Manual Installation • 9
Junction Box
Use the junction box to install the HCN transmitter at a mounting site that is remote from the
controller. The junction box protects the amplifier and wiring connections made to the amplifier.
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. Three spacers
installed on the back of the junction box control the distance of the junction box from a mounting
surface and ensure that there is enough room to install a calibration cup on the detector during
calibration.
Installation
This section describes procedures to mount the HCN transmitter in the monitoring environment
and wire the detector to a controller.
Mounting the HCN 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 detector 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 that is at normal breathing level.
Figure 3: Mounting the HCN Detector
.38
.75
3.10
J-Box
3/4 NPT
Female
Rubber
Spacers
3X
3.65
HCN Detector
11/2-20Threadfor
Calibration Cup
8.18 Max

10 • Installation 65-2333 Hydrogen Cyanide Transmitter Operator’s Manual
2. At the monitoring site you select, hang or mount the junction box with the detector facing
down (see Figure 3).
Wiring the HCN Transmitter to a Controller
WARNING: Always verify that power to the controller is OFF before you make wiring
connections.
1. Turn off the controller.
2. Turn off 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 4.
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 terminal strip is keyed so that the controller and
detector terminal strips cannot be reversed inadvertently.
WARNING: To maintain the explosion proof classification of the HCN detector/junction
box combination, a conduit seal must be used within 18 inches of the junction
box conduit hub used for wiring to the controller.
6. Guide a two-conductor, shielded cable, or two wires in conduit through the top conduit hub of
the junction box.
7. Pull out the controller terminal strip and connect the two wires to the terminal strip as follows
(see Figure 4).
• Connect the positive wire to the terminal labeled SIG/PWR “+” terminal.
• Connect the signal wire to the terminal labeled SIG/PWR “S” terminal.
CAUTION: If a shielded cable is used, leave the cable shield’s drain wire insulated
and disconnected 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 HCN 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.

65-2333 Hydrogen Cyanide Transmitter Operator’s Manual Installation • 11
11. Connect the wires to the applicable detector/transmitter terminal strip at the controller as
shown in Figure 4.
Figure 4: Wiring the HCN Transmitter to a Controller
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.
S
ZERO SPAN SIG/PWRTO X IC O XY
Black
Red
Controller Detector/Transmitter
Terminals, Typical Designations S
Controller
Cable Shield
J-Box
HCN Detector
+

12 • Start Up 65-2333 Hydrogen Cyanide Transmitter Operator’s Manual
Start Up
This section describes procedures to start up the HCN transmitter and place the transmitter into
normal operation.
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 power to the controller.
4. Turn on the controller.
5. Verify that the controller is on and operating properly. Refer to the controller operator’s
manual.
CAUTION: Allow the transmitter to warm up for 5 minutes before you continue with
the next section, “Setting the Zero Signal”.
Setting the Zero Signal
WARNING: Do not remove the detector housing cap or junction box cover while the circuits
are energized unless the area is determined to be non-hazardous. Keep the
detector housing cap and junction box cover tightly closed during operation.
NOTE: If you can verify that the detector is in a fresh air environment (environment known to
be of normal oxygen content and free of toxic and combustible gases), it is not
necessary to apply zero air when verifying or setting the fresh air reading.
The procedure below describes applying zero emission air, usually called zero air, 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.
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 HCN detector.
5. Screw the regulator into the zero air calibration cylinder.
6. Use the sample tubing to connect the regulator to the calibration cup.

65-2333 Hydrogen Cyanide Transmitter Operator’s Manual Maintenance • 13
7. Turn the regulator’s on/off knob counterclockwise to open it. Gas will begin to flow.
8. Allow the gas to flow for two minutes.
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 HCN transmitter. It includes daily and quarterly procedures.
Daily
Verify a display reading of 0 ppm HCN at the controller. Investigate significant changes in the
display reading.
Quarterly
Calibrate the HCN transmitter as described in “Calibration” on page 19. See the calibration
frequency discussion in “Calibration Frequency” on page 18 to determine if a quarterly
calibration schedule fits your needs.

14 • Maintenance 65-2333 Hydrogen Cyanide Transmitter Operator’s Manual
Troubleshooting
The troubleshooting guide describes symptoms, probable causes, and recommended action for
problems you may encounter with the HCN transmitter.
NOTE: This troubleshooting guide describes transmitter problems only. See the controller
operator’s manual for problems you may encounter with the controller.
Table 2: Troubleshooting HCN Detector
Condition Symptom(s) Probable Causes Recommended Action
Fail Condi-
tion
• Controller indicates
a fail condition.
• The transmitter
wiring to the
controller is
disconnected or
misconnected.
• The plug-in sensor is
not properly plugged
into the sockets in
the detector housing
body.
• The wiring from the
detector to the
amplifier is
disconnected or
misconnected.
• The transmitter’s
zero reading is low
enough to cause a
fail condition.
• The transmitter is
malfunctioning.
1. Verify that the transmitter wiring
to the controller is correct and
secure.
2. Confirm that the plug-in sensor is
installed properly.
3. Verify that the wiring from the
detector to the amplifier is correct
and secure.
4. Perform a fresh air adjustment. A
full calibration is recommended.
5. If the fail condition continues,
replace the plug-in sensor as
described later in this section.
6. If the fail condition continues,
contact RKI for further
instruction.

65-2333 Hydrogen Cyanide Transmitter Operator’s Manual Maintenance • 15
Replacing Components of the HCN Transmitter
This section includes a procedure to replace the HCN plug-in sensor and amplifier. A procedure to
replace the entire detector assembly is at the end of this section. In most cases, it is not necessary
to replace the entire detector assembly.
Replacing the Plug-In HCN Sensor
CAUTION: The sensor contains electrolyte which is a dilute acid. Do not disassemble the
sensor when replacing it with a new one. If sensor electrolyte comes in contact with
your skin, wash affected area thoroughly with soap and water.
1. Turn off the controller.
2. Turn off or unplug power to the controller.
3. Unscrew the detector housing cap from the detector housing body. Make sure not to lose the
cap gasket.
Slow or No
Response/
Difficult or
Unable to
Calibrate
• 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 3 months.
Some applications
may require a more
frequent calibration
schedule.
• The calibration
cylinder is low, out-
dated, or defective.
• The flame arrestor in
the detector housing
cap is wet or clogged
with dirt or other
particulates.
• 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. Examine the detector housing
cap. If it is only saturated with
liquid, dry it out. If it appears
dirty, replace it.
3. Replace the flame arrestor if it
appears dirty or saturated with
liquid.
4. Examine the VersaporR
membrane and replace it if it
appears dirty.
5. Verify that the calibration gas
concentration is appropriate for
the transmitter. Zero emission air
(20.9% oxygen) is normally used
for a zero adjustment if the
environment is suspect and 10
ppm HCN in nitrogen is normally
used for a span adjustment.
6. If the calibration/response
difficulties continue, replace the
plug-in sensor as described later
in this section.
7. If the calibration/response
difficulties continue, contact RKI
for further instruction.
Condition Symptom(s) Probable Causes Recommended Action

16 • Maintenance 65-2333 Hydrogen Cyanide Transmitter Operator’s Manual
4. Unplug and remove the HCN sensor with the rubber boot and spacer attached.
5. Remove the rubber boot and spacer from the old sensor.
6. Remove the replacement sensor from its packaging and remove the wire jumper. This wire
jumper is installed on the sensor pins for shipment or storage but must be removed for the
sensor to operate properly when installed in a detector.
WARNING: The HCN sensor will not operate properly if the wire jumper is not removed.
7. Install the spacer and rubber boot onto the replacement sensor’s face.
8. Carefully plug the replacement sensor into the four-socket pattern that is located in the
detector housing.
9. Make sure the cap gasket is in place and screw the detector housing cap back onto the detector
housing body.
10. Turn on or plug in power to the controller.
11. Turn on the controller and place into normal operation.
CAUTION: Allow the replacement sensor to warm up for 15 minutes before you
continue with the next step.
12. Calibrate the transmitter as described in the “Calibration” on page 19.
Replacing the VersaporR Membrane
1. Turn off the controller.
2. Turn off or unplug incoming power to the controller.
3. Unscrew the detector housing cap from the detector housing body.
4. Unplug the plug-in sensor from the four-socket pattern in the detector housing body.
5. Gently pry up the edge of the white VersaporR membrane from the sensor face with a small
flat blade screwdriver or a similar tool.
6. Peel off the VersaporR membrane. It may be necessary to clean off the sensor face to remove
any residue left from the adhesive backed membrane.
7. Install the new membrane on the face of the plug-in sensor.
8. Plug the sensor back into the four-socket pattern in the detector housing body.
Figure 5: Plug-In Sensor Jumper Removal
Remove jumper

65-2333 Hydrogen Cyanide Transmitter Operator’s Manual Maintenance • 17
9. Make sure the cap gasket is in place and screw the detector housing cap back onto the detector
housing body.
10. Turn on power to the controller.
11. Turn on the controller.
Replacing the HCN Detector
NOTE: In most cases, it is only necessary to replace the plug-in HCN sensor.
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 conduit hub.
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 appropriate detector terminal strip terminals. Connect the red
wire to the terminal labeled TOXIC + and the black wire to the terminal labeled TOXIC -. See
Figure 4 for the detector wiring connections to the amplifier.
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 15 minutes before you
continue with the next step.
13. Calibrate the replacement detector as described in “Calibration” on page 19.
Replacing the Amplifier
1. Turn off the controller.
2. Turn off or unplug power to the controller.
3. Remove the junction box cover.

18 • Calibration Frequency 65-2333 Hydrogen Cyanide Transmitter Operator’s Manual
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. The screw is at the bottom right of the amplifier.
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.
9. Install the detector and controller terminals strips into their sockets on the new amplifier as
shown in Figure 4. If controller leads or detector leads were removed during this procedure,
refer to Figure 4 for the detector and amplifier connections.
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 or plug in 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 HCN transmitter as described in the “Calibration” on page 19.
Calibration Frequency
Although there is no particular calibration frequency that is correct for all applications, a
calibration frequency of every 3 months is adequate for most HCN transmitter applications.
Unless experience in a particular application dictates otherwise, RKI Instruments, Inc.
recommends a calibration frequency of every 3 months for the HCN transmitter.
If an application is not very demanding, for example detection in a clean, temperature controlled
environment, and calibration adjustments are minimal at calibration, then a calibration frequency
of every 6 months is adequate.
If the application is very demanding, for example if the environment is not well controlled, then
more frequent calibration than every 3 months may be necessary.

65-2333 Hydrogen Cyanide Transmitter Operator’s Manual Calibration • 19
Calibration
This section describes how to calibrate the HCN transmitter. It includes procedures to prepare for
calibration, set the zero reading, set the response reading, and return to normal operation. It
describes the test 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.
Preparing for Calibration
NOTE: Calibrating the HCN transmitter may cause alarms. Be sure to put the controller into its
calibration program or disable external alarms before calibration.
WARNING: Do not remove the detector housing cap or junction box cover while the circuits
are energized unless the area is determined to be non-hazardous. Keep the
detector housing cap and junction box cover tightly closed during operation.
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 10 ppm HCN and a fullscale setting of 15 ppm,
the correct output is 200 mV.
366.7 (mV) = (10/15) X 400 +100
5. Screw the calibration cup onto the detector housing.
Setting the Zero Reading
NOTE: If you can verify that the HCN transmitter is in a fresh air environment, you do not need
to apply zero air to the detector before adjusting the zero reading.
1. Screw the regulator into the zero air calibration cylinder.
2. Use the sample tubing to connect the regulator to the calibration cup.
3. Turn the regulator knob counterclockwise to open the regulator.
4. Allow the gas to flow for two minutes, then verify a reading of 100 mV (± 2mV). If necessary,
use the zero pot on the amplifier to adjust the reading to 100 mV (± 2mV).

20 • Calibration 65-2333 Hydrogen Cyanide Transmitter Operator’s Manual
5. Unscrew the regulator from the zero air calibration cylinder.
6. Leave the sample tubing connected to the regulator and the calibration cup.
Setting the Response Reading
1. Verify that the calibration gas is representative of the transmitter’s target gas.
2. For toxic gas cylinders (like HCN), it is important to vent the regulator while installing it onto
the cylinder. Venting the regulator during installation helps prevent air from getting into the
cylinder and degrading the gas. Open the regulator by turning the knob counterclockwise and
then install it onto the cylinder.
3. Allow the gas to flow for two minutes, then verify that the reading matches the response
reading (± 2mV) 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 knob clockwise to close the regulator.
5. Unscrew the regulator from the calibration cylinder.
Returning to Normal Operation
1. Remove the voltmeter leads from the amplifier test points.
2. Unscrew the calibration cup from the detector.
NOTE: For convenience, leave the components of the calibration kit connected by
the sample tubing.
3. Secure the junction box cover to the junction box.
4. When the display reading falls below the alarm setpoints, return the controller to normal
operation.
5. Verify that the controller display reading decreases and stabilizes at 0 ppm.
6. Store the components of the calibration kit in a safe and convenient place.