RKI Instruments AirLink 6940NXP User manual

RKI Instruments, Inc.
www.rkiinstruments.com
AirLink 6940NXP
Operator’s Manual
Part Number: 71-0591
Revision: P1
Released: 4/14/22

AirLink 6940NXP Operator’s Manual • 2
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. For most applications,
typical calibration frequencies are between 3 and 6 months but can be
more often or less often based on your usage.

3• AirLink 6940NXP Operator’s Manual
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.

AirLink 6940NXP Operator’s Manual • 4
Caution Statements
WARNING: EXPLOSION HAZARD - SUBSTITUTION OF COMPONENTS MAY IMPAIR
SUITABILITY FOR CLASS I, DIVISION 1, or equivalent as stated in user
manual.
AVERTISSEMENT: RISQUE D'EXPLOSION-LA SUBSTITUTION DE COMPOSANTS
PEUT RENDURE CE MATERIEL INACCEPTABLE POUR LES
EMPLACEMENTS DE CLASSE I, DIVISION I.
CAUTION: For safety reasons, this equipment must be operated and serviced by qualified
personnel only. Read and understand the instruction manual completely before
operating or servicing.
ATTENTION: POUR DES RAISONS DE SECURITE, CET ÉQUIPEMENT DOIT ETRE
UTILISE ENTRETENU ET REPARER UNIQUEMENT PAR UN PERSONNEL QUALIFIE.
ETUDIER LE MANUEL D' INSTRUCTIONS EN ENTIER AVANT D' UTILISER, D'
ENTERETENIR OU DE RÉPARER L' ÉQUIPEMENT.
CAUTION: THIS AREA MUST BE FREE OF FLAMMABLE GASES DURING CALIBRATION.
ATTENTION: CETTE ZONE DOIT ETRE EXEMPTE DE GAZ INFLAMMABLES
PENDANT L'ETALONNAGE.
CAUTION: TO PREVENT IGNITION OF EXPLOSIVE ATMOSPHERES, remove from
explosive atmosphere BEFORE SERVICING.
WARNING: A conduit seal must be used within 18 inches of the enclosure wall to comply with
the hazardous location rating of this product.
Danger Statements
DANGER: The RKI Instruments Inc. AirLink 6940NXP is an ambient air Hazardous gas sensor
assembly and only monitors in the immediate vicinity of the sensor housing. A site survey is
required in order to determine the best placement and quantity of sensor assemblies. Improper
installation can lead to an undetectable gas leak which could result in personal injury or loss of
life.

5• AirLink 6940NXP Operator’s Manual
Table of Contents
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
External Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Internal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Remote-Mounted Kit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Mounting the AirLink 6940NXP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Remote-Mounted Kit Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Connecting AC Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Connecting the Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Closing the Enclosure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Normal Operating Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Magnetic Buttons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Powering the Device. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Faults. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Above Background Display Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Accessing the Settings Menus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Global Settings and Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Global Settings Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Network ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Unit Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Display Screen Contrast Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Return to Factory Default Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Exiting the Global Settings Menu. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Sensor Settings and Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
Sensor Settings Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Turning the Sensor On/Off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

AirLink 6940NXP Operator’s Manual • 6
Zeroing the Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Calibrating the Sensor (Manual Cal) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Calibrating the Sensor (Auto Cal) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Sensor Radio Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Sensor Alarm Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Sensor Background Setting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Calibration Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Sensor Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Last Zero/Cal Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Reset Sensor Zero/Cal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Exiting the Sensor Settings Menu. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Maintenance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Replacing the Desiccant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Replacing the Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Cleaning the 10.0 eV or 10.6 eV PID Lamp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Replacing the PID Lamp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Replacing the PID Electrode Stack. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Replacing the Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69

7• Overview AirLink 6940NXP Operator’s Manual
Overview
The RKI Instruments, Inc. AirLink 6940NXP explosion-proof ambient air hazardous gas detector
is designed to detect up to 4 different types of toxic gases in potentially hazardous environments.
In this manual, the instructions reference the use of push-buttons, located on the front panel of the
device. In certain environments, the activation of the non-intrusive magnetic switches, through
the use of the magnetic tool, will replace the directive of the button-press actions. To apply the
magnetic tool, hold the tool to the side of the device enclosure adjacent to the push-button that
you wish to activate. When the magnetic switch is toggled, an on-screen indicator will appear on
the display screen, signifying that a connection was made.
The AirLink 6940NXP continuously monitors the gas level of the surrounding environment and
reports once every minute. The reporting rate will increase to once every five seconds when the
detected gas is above the Background Gas set-point. This set-point is adjustable (per sensor) to
account for sites with a constant, low-level of gas, allowing the AirLink 6940NXP to maintain a
long battery life (when not operating on AC power). When the gas level passes below or above
(for O2) every sensor’s set-point, the reporting rate will return to once every minute. The AirLink
6940NXP display will always show the present concentration of gas being detected by the sensor
assembly.
This document is an operation manual containing diagrams and step-by-step instructions for the
proper and safe installation, start-up, configuration, normal operation, and product maintenance
of the AirLink 6940NXP.
NOTE: This document should be read in its entirety before the initial operation of the product.

AirLink 6940NXP Operator’s Manual Specifications • 8
Specifications
Table 1 lists specifications for the AirLink 6940NXP.
Table 1: Specifications
Target Gas Detection Range Increment Haz. Loc. Alarm Points
(1 / 2 / 3 / 4)*
Ammonia (NH3) 0-100 ppm 1 ppm Cl. 1 Div. 2 12 / 25 / 50 / 100 ppm
0-1,000 ppm 35 / 300 / 300 / 1,000 ppm
Arsine (AsH3) 0-1.00 ppm 0.01 ppm 0.2 / 0.5 / 1.0 / 1.0 ppm
Carbon Dioxide (CO2) 0-5.0% volume 0.1% volume Cl. 1 Div. 1 0.5 / 3.0 / 3.0 / 5.0 % volume
Carbon Monoxide (CO) 0-1,000 ppm 1 ppm 1,000 / 1,000 / 1,000 / 1,000
ppm
Chlorine (Cl2) 0-10.0 ppm 0.1 ppm Cl. 1 Div. 2 1 / 3 / 5 / 10 ppm
Chlorine Dioxide (ClO2) 0-1.00 ppm 0.01 ppm 0.1 / 0.3 / 0.3 / 1.0 ppm
Combustible Gas 0-100% LEL 1% LEL Cl. 1 Div. 1 10 / 20 / 50 / 100% LEL
0-100% volume 1% vol. 100 / 100 / 100 / 100%
Ethylene Oxide (EtO) 0-10.0 ppm 1.0 ppm Cl. 1 Div. 2 1 / 3 / 5 / 10 ppm
Formaldehyde (CH2O) 0-10.00 ppm 0.01 ppm 0.5 / 2 / 5 / 10 ppm
Hydrogen 0 - 100% LEL 1% LEL Cl. 1 Div. 1 10 / 20 / 50 / 100% LEL
Hydrogen Chloride (HCl) 0-20 ppm 1 ppm Cl. 1 Div. 2 5 / 10 / 10 / 20 ppm
0-100 ppm 5 / 10 / 30 / 100 ppm
Hydrogen Cyanide (HCn) 0-50 ppm Cl. 1 Div. 1 5 / 10 / 15 / 50 ppm
Hydrogen Fluoride (HF) 0-10.0 ppm 0.1 ppm Cl. 1 Div. 2 3 / 6 / 6 / 10 ppm
Hydrogen Sulfide (H2S) 0-10.0 ppm 0.1 ppm Cl. 1 Div. 1 1 / 5 / 10 / 10 ppm
0-25 ppm 1 ppm 5 / 10 / 10 / 25 ppm
0-50 ppm 5 / 10 / 10 / 50 ppm
0-100 ppm 10 / 50 / 75 / 100 ppm
0-500 ppm 100 / 200 / 200 / 500 ppm
0-2,000 ppm 100 / 200 / 200 / 2,000 ppm
Nitric Oxide (NO) 0-250 ppm Cl. 1 Div. 2 25 / 50 / 100 / 250 ppm
Nitrogen Dioxide (NO2) 0-20.0 ppm 0.1 ppm Cl. 1 Div. 2 5 / 10 / 10 / 20 ppm

9• Specifications AirLink 6940NXP Operator’s Manual
Oxygen (O2) 0-25.0% volume 0.1% volume Cl. 1 Div. 1 19.5% dec. / 23.5% inc. /
17.0% dec. / 25.0% inc.
Ozone (O3) 0-5.0 ppm 0.1 ppm Cl. 1 Div. 2 1 / 3 / 5 / 5 ppm
0-100 ppm 1 ppm 10 / 15 / 15 / 100 ppm
Phosphine (PH3) 0-5.0 ppm 0.1 ppm Cl. 1 Div. 1 0.3 / 1.0 / 1.0 / 5.0 ppm
Sulfur Dioxide (SO2) 0-20 ppm 1 ppm 2 / 5 / 5 / 20 ppm
Volatile organic com-
pounds (VOCs), benzene
calibration standard
10.0 eV Lamp
0 - 10 ppm 0.01 ppm Cl. 1 Div. 1 1 / 1.5 / 1.5 / 10 ppm
0 - 20 ppm 2 / 3 / 3 / 20 ppm
0 - 50 ppm 5 / 7.5 / 7.5 / 50 ppm
0 - 100 ppm 1 ppm 10 / 15 / 15 / 100 ppm
Volatile organic com-
pounds (VOCs), isobuty-
lene calibration standard
Low Range 10.6 eV Lamp
0 - 10.00 ppm 0.01 ppm Cl. 1 Div. 1 1 / 1.5 / 1.5 / 10 ppm
0 - 20.00 ppm 2 / 3 / 3 / 20 ppm
0 - 50.00 ppm 5 / 7.5 / 7.5 / 50 ppm
High Range 10.6 eV Lamp
0 - 100 ppm 1 ppm Cl. 1 Div. 1 10 / 15 / 15 / 100 ppm
0 - 200 ppm 20 / 30 / 30 / 200 ppm
0 - 500 ppm 50 / 75 / 75 / 500 ppm
0 - 1,000 ppm 100 / 150 / 150 / 1,000 ppm
0 - 2,000 ppm 200 / 300 / 300 / 2,000 ppm
11.7 eV Lamp
0 - 100 ppm 0.01 ppm Cl. 1 Div. 1 10 / 15 / 15 / 100 ppm
* Alarms are only programmable at a controller and do not affect operation of the AirLink 6940NXP.
Sampling Method Diffusion
Enclosure Ratings • Explosion/Flame-Proof
Power Source • Primary - 115-220 VAC 0.35A
• Backup - Lithium-thionyl (Li-SOCl2) battery pack, 3.6 VDC 76 Ah
Table 1: Specifications
Target Gas Detection Range Increment Haz. Loc. Alarm Points
(1 / 2 / 3 / 4)*

AirLink 6940NXP Operator’s Manual Specifications • 10
WARNING: When using the AirLink 6940NXP, you must follow the instructions and
warnings in this manual to assure proper and safe operation of the AirLink
6940NXP and to minimize the risk of personal injury. Be sure to maintain and
periodically calibrate the AirLink 6940NXP as described in this manual.
Battery Life (when used
as the primary power
source)
6 months (45 days for versions with PID)
NOTE: When the battery indicator is blank, approximately 2 weeks of battery life remain.
Operating
Temperature Range
-40°C to +60°C (-40°F to +140°F)
Humidity Range 0 - 98% relative humidity, non-condensing
Radio Output
• 900 MHz - 52 networks, 255 sensors per network
OR
• 2.4 GHz - 78 networks, 255 sensors per network
RF Connection N-female radio frequency (RF) connector
Display
Transreflective (sunlight-readable)
160 x 104 LCD screen
LED back-light
Max Cable Length for
Remote-Mounted
Antenna
100 feet
Enclosure Material Polycarbonate enclosure with clear lid
Sensor Housing
Material
Black polypropylene plastic with SS mesh screen
Max Cable Length for
Remote-Mounted
Sensor Kit
• Electrochemical (EC): 250 feet
• Infrared (IR): 40 feet
• PID: 35 feet
Dimensions 7” D x 10” W x 20” H
Weight 5 lbs.

11 • External Description AirLink 6940NXP Operator’s Manual
External Description
Figure 1: AirLink 6940NXP External Component Locations
1Radio antenna - 900 MHz or 2.4 GHz 11 ADD magnet switch location
2Mounting feet 12 MENU magnet switch location
3Door latch 13 ADD push button
4BACK magnet switch location 14 MENU push button
5SUB magnet switch location 15 BACK push button
6AC power cable 16 SUB push button
7Sensor Housing Cap Number 4 17 Thumbscrews (2)
8Sensor Housing Cap Number 3 18 Display screen
9Sensor Housing Cap Number 2 19 Enclosure door
10 Sensor Housing Cap Number 1 20 Magnetic tool

AirLink 6940NXP Operator’s Manual Internal Description • 12
Internal Description
Figure 2: Internal Component Locations
1Enclosure door 8Terminal board assembly
2Faceplate 9Backup battery pack
3Antenna fitting connector 10 Battery pack restraining strap
4Radio module 11 Sensor connector (Up to 4)
5Battery pack plug 12 Sensor connector cable (Up to 4)
6Antenna fitting 13 Control board assembly
7AC power supply

13 • Remote-Mounted Kit AirLink 6940NXP Operator’s Manual
Remote-Mounted Kit
A remote-mounted sensor kit can be ordered if the sensor needs to be somewhere that is not
conveniently accessible for viewing the display screen.
The kit includes a second junction box on a cable with a cable bushing/cable gland. The cable can
be ordered in 1-foot increments with maximum cable lengths listed below.
Installation
This section describes procedures to mount the AirLink 6940NXP in the monitoring environment
and wire the AirLink 6940NXP.
Mounting the AirLink 6940NXP
1. Consider the following when you select the mounting location:
• The unit should be placed greater than 6.5 feet/2 meters away from a monitor in order to
ensure reliable communications.
• Select a site where the AirLink 6940NXP 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 representative of the monitoring environment and where the target gas
is likely to accumulate or where it is most likely to leak. The AirLink 6940NXP should not
be installed near an entrance, air intake, or exhaust point.
• When monitoring “light” hydrocarbons, such as methane, the unit should be placed near
the ceiling or ceiling corner.
• When monitoring “heavy” hydrocarbons, such as gasoline, the unit should be placed
approximately 2 to 3 inches from the floor.
• The sensor must point down.
• Avoid installing the AirLink 6940NXP in a location where airborne particles could cover
or coat the sensor.
NOTE: These guidelines are ONLY intended as a general directive for the
placement of the AirLink 6940NXP. This information should NOT serve as
a complete list when considering all potential parameters for the proper
location of the unit. It is STRONGLY advised that a third party Certified
Industrial Hygienist, or other Certified Safety Professional, conduct a site
survey and annotate the location and quantity of detection devices that
should be installed for EVERY installation of EVERY site.
Sensor Type Max Cable Length
Electrochemical (EC) 250 feet
Infrared (IR) 40 feet
PID 35 feet

AirLink 6940NXP Operator’s Manual Installation • 14
2. Select a mounting location and installation hardware. Mounting to a concrete or steel structure
is recommended to minimize vibration and moisture. Use a maximum 1/4” diameter bolt or
screw, flat washers, Grade 5 material (minimum), and corrosion protection (paint,
galvanization, or zinc plating).
Figure 3: AirLink 6940NXP Dimensions

15 • Installation AirLink 6940NXP Operator’s Manual
3. For a remote-mounted kit, install the detector junction box at the monitoring environment
using techniques appropriate for the local electrical code.
Figure 4: Remote-Mounted Kit’s Detector Junction Box Dimensions
Ø0.20
3.29
4.54

AirLink 6940NXP Operator’s Manual Installation • 16
Remote-Mounted Kit Wiring
The remote-mounted kit generally comes prewired, but if it becomes disconnected, follow these
steps to reconnect it.
CAUTION: The internal components can be static sensitive. Use caution when opening the
enclosure and handling internal components.
CAUTION: Make sure the power source is off before beginning the wiring procedure.
1. Release the housing latches, open the housing door, and unscrew the thumbscrews to access
the amplifier junction box's internal components.
2. Unscrew the captive screws from the detector junction box. Remove the enclosure lid and set
it aside.
3. At the amplifier junction box, use the handles to gently lift the internal system out of the
enclosure. It can rest on the edge of the enclosure.
4. One end of the cable has a connector and the other has ferruled wires.
5. Feed the connector end of the cable through a conduit hub at the amplifier junction box.
6. Plug the connector into the sensor connector socket at the amplifier junction box.
7. Feed the ferruled-wire end of the cable through a conduit hub at the detector junction box.
8. Connect the ferruled wires to the color-coded terminals in the detector junction box.
9. Reinstall the detector junction box's lid by tightly screwing the captive screws into the
enclosure base.
10. To close the amplifier junction box, tighten the thumbscrews, close the housing door, and
secure the latches.
Connecting AC Power
It is recommended that the AirLink 6940NXP be connected to AC Power (115-220 VAC 0.35A)
as its primary power source.
Before using the instrument, ensure that the unit’s AC power cord is securely plugged into the
power source. If the unit’s AC power is disrupted, the unit can also be powered by the internal
backup battery pack.

17 • Installation AirLink 6940NXP Operator’s Manual
Connecting the Battery
While the AirLink 6940NXP is primarily connected to AC Power, the instrument can also be
powered by an internal 3.6V/76AH lithium-thionyl battery pack. This backup battery pack is
already installed upon shipment but with the wiring disconnected.
CAUTION: The internal components can be static sensitive. Use caution when opening the
enclosure and handling internal components.
CAUTION: Use only RKI-supplied batteries.
1. Release the housing latches, and open the enclosure door.
2. Unscrew the faceplate thumbscrews and pull open the faceplate to access the internal system.
3. Locate the battery terminal on the terminal board assembly. Plug the battery cable connector
into the battery terminal.
Figure 5: Battery Connection
4. Push the faceplate closed and screw the faceplate thumbscrews back into place.
5. Close and relatch the enclosure door.
6. The unit will start in OFF mode. Press and hold ADD to initiate the startup.
Closing the Enclosure
1. Push the faceplate closed and screw the faceplate thumbscrews back into place.
2. Close and relatch the enclosure door.

AirLink 6940NXP Operator’s Manual Start Up • 18
Start Up
This section describes procedures to start up the AirLink 6940NXP and place the device into
normal operation.
1. Complete the installation procedures described earlier in this manual.
2. Verify that the battery connection is correct and secure and that the AC power cord is plugged
in if desired.
3. Verify that the controller is on and operating properly. Refer to the controller operator’s
manual.
4. Press and hold ADD for approximately 6 seconds to turn the AirLink 6940NXP on. The unit
enters a 1-minute startup period (3.5 minutes for LEL).
5. At the end of the startup, the AirLink 6940NXP enters Normal Operating Mode.
6. Allow the installation to warm up for the appropriate amount of time as indicated in the table
below. For units with multiple sensors, the warm up period is based on the installed sensors
with the longest warm up time.
Detection Gas
Warm Up Time
After an Extended
Time Off Power
Warm Up Time
After a Short Time
Off Power
Ammonia (NH3) 12 hours 4 hours
Arsine (AsH3) 2 hours 10 minutes
Carbon Dioxide (CO2) 10 minutes
Carbon Monoxide (CO) 2 hours
Chlorine (Cl2)
Chlorine Dioxide (ClO2)
Combustible Gas 10 minutes

19 • Start Up AirLink 6940NXP Operator’s Manual
7. The AirLink 6940NXP is factory-calibrated before shipping from RKI. If a full calibration is
desired at startup, see page 34.
NOTE: The user interface will be slow to respond until the AirLink 6940NXP
establishes a connection with the controller.
Ethylene Oxide (EtO) 48 hours 10 minutes
Formaldehyde (CH2O) 10 minutes
Hydrogen (H2) 2 hours
Hydrogen Chloride (HCl) 12 hours
Hydrogen Cyanide (HCn)
Hydrogen Fluoride (HF) 2 hours
Hydrogen Sulfide (H2S)
Nitric Oxide (NO) 12 hours
Nitrogen Dioxide (NO2) 2 hours
Oxygen (O2)
Ozone (O3)
Phosphine (PH3)
Sulfur Dioxide (SO2)
VOCs 10 minutes
Detection Gas
Warm Up Time
After an Extended
Time Off Power
Warm Up Time
After a Short Time
Off Power

AirLink 6940NXP Operator’s Manual Operation • 20
Operation
Normal Operating Mode
While in Normal Operating Mode, the AirLink 6940NXP continuously samples the air and
updates the measured concentration of the target gas on the display screen. The display, when in
Normal Operating Mode, appears as shown below.
The gas reading is sent back to the controller in 1-minute intervals when the reading is below the
background setting (page 43). When the reading surpasses the background setting, the reading is
sent back to the controller in 5-second intervals.
NOTE: The user interface will be slow to respond until the AirLink 6940NXP establishes a
connection with the controller.
Table 2: Normal Mode Layout
1Battery Level indicator (Only visible
when back-light is off) 5Sensor gas type
2Network ID 6Gas concentration unit
3Sensor radio address 7Fault indication
4Sensor reading