MODEL: O2-25-24
ASSEMBLY CONSISTS OF:
XP-O2 housing (supersedes PE-EX-O2)
ST1400-500-24 sensor (supersedes PE1400-500-24)
JB2 junction box
CB2 connector board
ELECTROCHEMICAL O2 DETECTOR
(Used with ST1400 O2 Sensor)
Part Number: MAN-0028-00 Rev. 0
WARRANTY POLICY
Net Safety Monitoring Inc Products, are carefully designed and m anufactured from high quality
components and can be expected to provide many years of trouble free service. Each product is
thoroughly tested, inspected and burned-in prior to shipment. Failures can occur which are
beyond the control of the manufacturer. Failures can be minimized by adhering to the operating
and maintenance instructions herein. Where the absolute greatest of reliability is required,
redundancy should be designed into the system.
Net Safety Monitoring Inc, warrants its sensors and detectors against defective parts and
workmanship for a period of 24 months from date of purchase and other electronic assemblies for
36 months from date of purchase.
No other warranties or liability, expressed or implied, will be honored by Net Safety Monitoring Inc.
Contact Net Safety Monitoring Inc. or the authorized distributor for details.
Table of Contents
DESCRIPTION ............................................................... 1
FEATURES .................................................................. 1
Figure 1 - O2 Detector Assembly ........................................... 1
SPECIFI CATIONS ............................................................ 2
SENSOR OPERATION ......................................................... 2
SENSING ELEMENT .................................................... 2
SENSOR OUTPUT ..................................................... 2
I NSTALL ATION ............................................................... 3
DETECTOR POSITIONING ............................................... 3
WIRING REQUIREMENTS ............................................... 3
Table 1 -Maximum Wiring Distances Sensor to Controller/Transmitter ............. 3
SENSOR WIRING ...................................................... 3
Figure 2 - Sensor Wiring ................................................. 5
START-UP PROCEDURE ...................................................... 6
CALIBRA TION ............................................................... 6
MAINTENANCE .............................................................. 6
SENSING ELEMENT REPLACEMENT ...................................... 6
TROUBL ESHOOTING ......................................................... 7
Table 2 - Troubleshooting Guide ........................................... 8
Appendix A
Net Safety Monitoring Inc. Electrostatic Sensitive Device Handling Procedure . . . . . . . . . . . . . . . i
Appendix B
Wire Resistance In Ohms ........................................................ii
DESCRIPTION
The Net Safety Monitoring Inc. O2-25-24 Electrochemical O Detector consists of an explosionproof enclosure, which contains sensor electronic circuitry and an electrochemical O sensing
element. This O sensor provides continuous monitoring of oxygen levels in the range of 0 to
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2
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25%. The sensor can be used with one of the Net Safety Monitoring Inc. Uni-Trol™ Controllers or
Display Modules, or it can be used with other devices that are capable of monitoring a 4 to 20 mA
dc input and allow for calibration. The explosion-proof sensor is CSA certified Class 1, Division 1,
Groups C and D.
FEATURES
Electrochem ical sensor for increased accuracy and reliability.
High specificity to O reduces the chance of false alarms resulting from the presence of
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other gasses.
Temperature compensation to ensure consistent performance over the entire operating
temperature range.
Self-contained transmitter circuitry permits use without a separate transmitter.
Explosion-proof housing.
EMI/RFI hardening.
SPECIFICATIONS
Figure 1 - O Detector Assembly
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< Operating Range:
0 to 25%
< Response Time:
T90 response time <10 sec.
< Drift:
Less than 0.25% p.m. per month.
< Sensor Life:
Comm only 2 to 3 years.
< Operating Voltage:
24Vdc. Device can operate in the range 18 to 32Vdc.
Optional 12Vdc model available.
< Temperature Range:
Continuous Operation: -20ºC to +40ºC (-4ºF to +105ºF).
Intermittent Operation: -20ºC to +55ºC (-4ºF to +130ºF).
Recommended Storage: 0ºC to +20ºC (+32ºF to +68ºF).
< Humidity Range:
0 to 99% RH, non-condensing.
< Enclosure M aterial:
Anodized aluminum.
< Dimensions:
2.60 inches (6.6 cm) in width.
5.55 inches (14.1 cm ) in length.
Refer to Figure 1.
< Shipping Weight (approximate) :
Aluminum Housing: 2.5 pounds (1.1 kilograms).
Sensing element: 0.2 pounds (0.1 kilograms).
SENSOR OPERATION
SENSING ELEMENT
The electrochemical sensing element uses capillary diffusion barrier technology for detecting the
level of oxygen in the atmosphere. The electrochemical sensing element provides improved
accuracy and reliability, as well as extended calibration intervals when compared to ordinary solid
state type sensors.
The response of the sensing elem ent is highly specific to O . Since many commonly encountered
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gases have little, if any, effect on the electrical response of the sensor, false indications caused by
the presence of these gasses is greatly reduced. The sensor should not be used in areas with
high concentrations of SO or CO for long periods of time, as this will shorten the life of the
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sensor.
SENSOR OUTPUT
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The sensor housing contains the circuitry for generating a 4 to 20 mA dc output signal,
corresponding to levels of O from 0 to 25%. T he 4 to 20 m A output is an un-calibrated signal.
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Therefore, calibration capabilities must be provided by a transmitter, controller, or display module,
to be used with the sensor.
INSTALLATION
CAUTION
The electrochemical sen sor contains sem iconductor devices that are sensitive to electrostatic
discharge. Handle the device by the housing, taking care not to touch electronic components or
terminals. Refer to 'Electrostatic Sensitive Device Handling Procedure' in the Appendix for
further details.
DETECTOR POSITIONING
Proper detector positioning is essential for providing maximum protection. The most effective number
and placement of sensors varies depending on the conditions at the job site. The individual
performing the installation must rely on experience and common sense to determine the number of
detectors needed and the best detector location. Regardless of the location, the sensor should be
oriented with the flame arrestor pointing down.
WIRING REQUIREMENTS
Two wire cable is used for connecting the sensor to a transmitter, controller, or display module. The
use of shielded cable is highly recommended to protect against interference caused by extraneous
electrical "noise."
The maximum distance between the sensor and controller is limited by the resistance of the
connecting wiring, which is a function of the gauge of the wire being used. See below for the
maximum wiring distance allowed for a given wire size. If a transmitter is used, refer to the transmitter
manual for specific wiring instructions.
WIRE
SIZE
MAXIMUM SENSOR TO
CONTROLLER DISTANCE
(AW G) Feet Meters
18 5700 1750
16 9000 2800
TABLE 1 - Maximum Wiring Distances
Sensor to Controller/Transmitter
SENSOR WIRING
1. Determine the best mounting locations for the sensors.
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2. Mount the sensor junction box, allowing room between the junction box and the mounting
surface for the sensor and calibration cup. The junction box should be electrically connected
to earth ground.
3. Remove the cover from the junction box.
NOTE
Do not apply power to the system with the junction box cover removed unless the area has been
declassified.
4. Remove the cap from the sensor housing.
5. Remove the sensing element assembly from the packaging. Determine proper orientation
for the assembly, then carefully plug it into the sensor housing.
NOTE
Handle the sensing e lem ent assem bly carefully. To avoid possible damage, observe the normally
accepted procedures for handling electrostatic sensitive devices. Refer to 'Electrostatic Sensitive
Device Handling Procedure" in the Appendix for further information.
6. Place the cap back on the sensor housing. Do not over tighten.
7. Attach the sensor to the junction box. The sensor should be tight to ensure an explosion
proof housing, but do not over tighten.
NOTE
Coat sensor threads with an appropriate grease to ease installation, and also lubricate the junction
box cover threads to ensure a water-tight enclosure.
8. Connect the sensor wires to the sensor terminal inside the junction box. Connect the
controller wiring to the controller wiring terminal block. Refer to Figure 2 on the next page.
Connect the shield to earth ground at the controller end only. Under normal conditions, the
other end of the shield should not be connected at the sensor junction box unless such a
connection is required by local wiring codes.
W iring Code :
Red lead : '+', positive ve
Black lead : signal
Green lead : Chassis (earth) ground
9. Check the sensor wiring to ensure proper connections. Place the cover back on the junction
box.
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STA
RTUP
PR
Figure 2 - Sensor Wiring
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OCEDURE
1. Secure output loads that are actuated by the system to prevent activation of these devices.
2. Check all wiring for proper connection. Be sure that the sensor has been wired properly.
3. Apply power to the system and allow the sensor to operate for about an hour, then perform
the "Start-up Procedure" and "Calibration Procedure" as outlined in the transmitter, controller,
or display module m anual.
4. Place the system in normal operation.
CALIBRATION
Since each application is different, the length of time between regularly scheduled calibrations can
vary from one installation to the next. However, calibration must be performed :
C when a new system is initially put into service,
C when the sensing element is replaced, and
C if a transmitter or controller used with the sensor is replaced.
IMPORTANT
To ensure adequate protection, the O detection system must be calibrated on a regularly scheduled
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basis.
It is recommended that the sensor be calibrated one hour after power-up and every 30 days
thereafter. Calibration procedures are dependant on the transmitter, controller, or display module
being used. For best results, the sensor must be calibrated using normal oxygen levels (21%).
Follow the "Calibration Procedure" outlined in the manual supplied with the transmitter, controller, or
display module used with the sensor.
MAINTENANCE
To ensure reliable protection, it is important to check and calibrate the O detection system on a
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regularly scheduled basis. The frequency of these checks will vary depending on conditions such as
relative humidity, dirty or dusty environments, and concentration of contaminating gases such as S0
or CO .
2
Relative hum idity is an important factor in the life expectancy of a sensor. Constant exposure to
extrem ely dry conditions will shorten the sensor life. If possible sensors, that are operated in
extremely dry areas should periodically be rotated to moister environments. A sensor that has been
exposed to extremely dry environments and can no longer be spanned during calibration or has low
sensitivity can be treated. The sensor should be placed in a moistened sealed bag and put in the
refrigerator for 24 to 48 hours. If this does not help, the sensor must be replaced.
For protection from the environment, a rain shield should be used in out-door applications and a dust
cover should be used in dirty or dusty environments.
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SENSING ELEMENT REPLACEMENT
The sensing element assembly is not intended to be repaired. When calibration can no longer be
performed properly, the assembly must be replaced. Spare sensing element assemblies should be
kept on hand for field replacement.
Care should be taken in storing the spare sensing element assemblies. For maximum protection
against contamination and deterioration, they should not be removed from the original protective
packaging until the time of installation. To ensure maximum storage life, sensing elements should be
stored at a temperature between 0/C and +20/C (+32/F and +68/F) and a relative humidity between
15 and 90 percent.
The area must be de-classified or power to the sensor must be removed prior to replacing the sensing
element in a hazardous area.
To replace the sensing element in the O2-25-24 detector :
1. Rem ove power from the sensor.
2. Remove the cap from the sensor housing. The detector housing does not have to be
removed from the junction box.
3. Remove and discard the old sensing element assembly. Check for corrosion or
contam ination on the term inals inside the sensor enclosure; clean if necessary.
4. Determine the proper orientation for the new assembly, then carefully plug it in.
NOTE
Handle the sensing element assembly carefully. To avoid possible damage, observe the normally
accepted procedures for handling electrostatic sensitive devices. Refer to “Electrostatic Sensitive
Device Handling Procedure” for further information.
5. Place the cap back on the sensor housing. Tighten only until snug; do not over tighten.
6. Re-apply power.
7. Allow time for the sensor to warm-up (approximately one hour for best results), then calibrate.
Always calibrate after replacing the sensing element.
NOTE
The sensing element assembly contains an acid that occasionally can leak. If a leakage should occur,
handle the assem bly c arefully to prevent any acid from contacting the skin. If acid should come in
contact with the skin, wash the affected area thoroughly with soap and water. Never attempt to open
the sensing element assembly.
TROUBLESHOOTING
Refer to Table 2 'Troubleshooting Guide'.
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Troubleshooting Guide
PROBLEM RECOMMENDATION
No 4 - 20 mA output. 1. Check the 24Vdc power input. Recall +ve goes to red and
signal goes to black.
2. Check that the green LED on the sensor is on. If off, check
wiring, especially the polarity. Also check for proper
connection at the sensor's plug-in connector in the junction
box.
Fluctuating current
output.
1. Check that all connections are good.
2. Check for AC noise interference on the cable. If noise does
appear, contact your local distributer for assistance.
Cannot zero on
calibration.
1. If used with a transmitter, controller, or display module,
check for AC noise on the cable. If noise does appear,
contact your local distributer.
Cannot span on
calibration.
1. Check the current output from the sensor. If it is low, the
sensor may have been exposed to an extremely dry
environment. Treat as outlined in the 'Maintenance' section.
Low sensitivity. 1. Sensor may have been exposed to an extremely dry
environment. Treat as outlined in the 'Maintenance' section.
2. Check for a dirt deposit on the flam e arrestor. Clean if
necessary. Use a dust cover in dirty or dusty environments,
or a rain shield out-doors.
TABLE 2 - Troubleshooting Guide
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APPENDIX A
NET SAFETY MONITORING INC.
Electrostatic Sensitive Device Handling Procedure
With the trend toward increasingly widespread use of microprocessors and a wide variety of other
electrostatic sensitive semiconductor devices, the need for careful handling of equipment containing
these devices deserves more attention than it has received in the past.
Electrostatic damage can occur in several ways. The most familiar is by physical contact. Touching
an object causes a discharge of electrostatic energy that has built up on the skin. If the charge is of
sufficient magnitude, a spark will also be visible. This voltage is often more than enough to damage
some electronic components. Som e devices can be dam aged without any physical contact. Exposure
to an electric field can cause damage if the electric field exceeds the dielectric breakdown voltage of
the capacitive elements within the device.
In some cases, permanent damage is instantaneous and an imm ediate malfunction is realized. Often,
however, the symptoms are not immediately observed. Performance may be marginal or even
seemingly normal for an indefinite period of time, followed by a sudden and mysterious failure.
Damage caused by electrostatic discharge can be virtually elim inated if the equipm ent is handled only
in a static safeguarded work area and if it is transported in a package or container that will render the
necessary protection against static electricity. Net Safety Monitoring Inc. modules that might be
damaged by static electricity are carefully wrapped in a static protective material before being
packaged. Foam packaging blocks are also treated with an anti-static agent. If it should ever become
necessary to return the module, it is highly recommended that it be carefully packaged in the original
carton and static protective wrapping.
Since a static safeguarded work area is usually impractical in most field installations, caution should
be exercised to handle the module by its m etal shields, taking care not to touch electronic
components or terminals.
In general, always exercise all of the accepted and proven precautions that are normally observed
when handling electrostatic sensitive devices.
A warning label is placed on the packaging, identifying those units that use electrostatic sensitive
semiconductor devices.
Published in accordance with EIA standard 471
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Appendix B
Wire Resistance In Ohms
DISTANCE (FEET) AWG #20 AWG #18 AWG #16 AWG #14 AWG #12 AWG #10 AWG #8
100 1.02 0.64 0.40 0.25 0.16 0.10 0.06
200 2.03 1.28 0.08 0.51 0.32 0.20 0.13
300 3.05 1.92 1.20 0.76 0.48 0.30 0.19
400 4.06 2.55 1.61 1.01 0.64 0.40 0.25
500 5.08 3.20 2.01 1.26 0.79 0.50 0.31
600 6.09 3.83 2.41 1.52 0.95 0.60 0.38
700 7.11 4.47 2.81 1.77 1.11 0.70 0.44
800 8.12 5.11 3.21 2.02 1.27 0.80 0.50
900 9.14 5.75 3.61 2.27 1.43 0.90 0.57
1000 10.20 6.39 4.02 2.53 1.59 1.09 0.63
1250 12.70 7.99 5.03 3.16 1.99 1.25 0.79
1500 15.20 9.58 6.02 3.79 2.38 1.50 0.94
1750 17.80 11.20 7.03 4.42 2.78 1.75 1.10
2000 20.30 12.80 8.03 5.05 3.18 2.00 1.26
2250 22.80 14.40 9.03 5.68 3.57 2.25 1.41
2500 25.40 16.00 10.00 6.31 3.97 2.50 1.57
3000 30.50 19.20 12.00 7.58 4.76 3.00 1.88
3500 35.50 22.40 14.10 8.84 5.56 3.50 2.21
4000 40.60 25.50 16.10 10.00 6.35 4.00 2.51
4500 45.70 28.70 18.10 11.40 7.15 4.50 2.82
5000 50.10 32.00 20.10 12.60 7.94 5.00 3.14
5500 55.80 35.10 22.10 13.91 8.73 5.50 3.46
6000 61.00 38.30 24.10 15.20 9.53 6.00 3.77
6500 66.00 41.50 26.10 16.40 10.30 6.50 4.08
7000 71.10 44.70 28.10 17.70 11.10 7.00 4.40
7500 76.10 47.90 30.10 19.00 12.00 7.49 4.71
8000 81.20 51.10 23.10 20.20 12.70 7.99 5.03
9000 91.40 57.50 36.10 22.70 14.30 8.99 5.65
10 000 102.00 63.90 40.20 25.30 15.90 9.99 6.28
NOTE: RESISTANCE SHOWN IS ONE WAY. THIS FIGURE SHOULD BE DOUBLED WHEN
DETERMINING CLOSED LOOP RESISTANCE.
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2721 Hopewell Place NE
Calgary, Alberta, Canada, T1Y 7J7
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