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MODEL: SO -100ppm. Optional 20ppm and 10ppm
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Available in: 24Vdc Version / 12Vdc Version / 10 - 32Vdc
ASSEMBLY CONSISTS OF:
XP-SO2 housing (supersedes PE-EX-SO2)
ST1300-XXX sensor (supersedes PE1300-24-20)
JB2 junction box
CB2 connector board
ELECTROCHEMICAL SO2 DETECTOR
(Used with ST1300 SO2 Sensor)
Part Number: MAN-0027-00 Rev 1
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This manual is provided for informational purposes only. Although the information contained in this
manual is believed to be accurate, it could include technical inaccuracies or typographical errors.
Changes are, therefore, periodically made to the information within this document and incorporated
without notice into subsequent revisions of the manual. Net Safety Monitoring Inc assumes no
responsibility for any errors that may be contained within this manual.
This manual is a guide for the use of a Toxic Gas Transmitter and the data and procedures contained within
this document have been verified and are believed to be adequate for the intended use of the transmitter. If the
transmitter or procedures are used for purposes other than as described in the manual without receiving prior
confirmation of validity or suitability, Net Safety Monitoring Inc does not guarantee the results and assumes
no obligation or liability.
No part of this manual may be copied, disseminated or distributed without the express written consent of Net
Safety Monitoring Inc
Net Safety Monitoring Inc products, are carefully designed and manufactured from high quality components
and can be expected to provide many years of trouble free service. Each product is thoroughly tested,
inspected and calibrated 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 an authorized distributor for details.
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Table of Contents
DESCRIPTION ...................................................................... 1
FEATURES ........................................................................ 1
SPECIFICATIONS ................................................................... 2
SENSOR OPERATION ............................................................... 3
SENSING ELEMENT ............................................................ 3
Table 1 - % Cross Sensitivity of Electrochemical Sensor
to Other Gases (SO = 100%) .................................................. 3
SENSOR OUTPUT ............................................................. 3
I NSTALLATION ..................................................................... 3
DETECTOR POSITIONING ...................................................... 3
WIRING REQUIREMENTS ....................................................... 4
Table 2 - Maximum Wiring Distances ............................................. 4
Sensor to Controller/Transmitter ................................................... 4
SENSOR WIRING .............................................................. 5
START-UP PROCEDURE ............................................................. 7
CALIB RATION ...................................................................... 7
MAINTENANCE ..................................................................... 7
SENSING ELEMENT REPLACEMENT .............................................. 8
TROUBL ESHOOTING ................................................................ 9
Table 3 - Troubleshooting Guide ................................................ 9
APPENDIX A Electrostatic Sensitive Device Handling Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
APPENDIX B Wire Resistance In Ohms ................................................. 11
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DESCRIPTION
The Net Safety Monitoring Inc. SO -100 Electrochemical SO Detector consists of an explosion-proof
enclosure, which contains sensor electronic circuitry and an electrochemical SO sensing elem ent. This
SO sensor provides continuous m onitoring of sulphur dioxide (SO ) concentrations in the range of 0 to
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100 parts per million (PPM) (optional 10 and 20 PPM). 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 for hazardous locations for Class 1, Division 1, Groups C and D.
FEATURES
< Electrochem ical sensor for increased accuracy and reliability.
< High specificity to SO reduces the chance of false alarms resulting from the presence of 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.
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Figure 1 - SO2 Detetctor Assembly
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SPECIFICATIONS
< Operating Range:
0 to 10, 20 and 100 ppm.
< Response Time:
T90 response time <20 sec.
< Drift:
Less than 2 ppm per month.
< Accuracy:
±10 percent of applied gas concentration or ±3 ppm , whichever is greater.
< Sensor Life:
Comm only 2 to 3 years.
< Operating Voltage:
10 to 32Vdc. 24Vdc nominal.
Optional 12Vdc model available.
< Temperature Range:
Continuous Operation: -20ºC to +50ºC (-4ºF to +122ºF).
Recommended Storage: 0ºC to +20ºC (+32ºF to +68ºF).
< Humidity Range:
Continuous: 15 to 90% RH, non-condensing.
Intermittent: 0 to 90% RH, non-condensing.
Storage: 15 to 90% RH, non-condensing.
< Enclosure Material:
Anodized aluminum.
< Dimensions:
2.60 inches (6.6 cm) in width.
5.55 inches (14.1 cm) in length.
Refer to Figure 1.
< Shipping W eight (approximate) :
Aluminum Housing : 2.5 pounds (1.1 kilograms).
Sensing element : 0.2 pounds (0.1 kilograms).
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SENSOR OPERATION
SENSING ELEMENT
The electrochemical sensing element uses capillary diffusion barrier technology for detecting the presence
of sulphur dioxide (SO2) gas. The electrochemical sensing element provides im proved accuracy and
reliability, as well as extended calibration intervals when compared to ordinary solid state type sensors.
The response of the sensing element is highly specific to SO . Since many commonly encountered gases
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have little, if any, effect on the electrical response of the sensor, false indications caused by the presence
of these gasses is greatly reduced. Below is a list of cross sensitivity of the electrochem ical sensor to
various other gases.
Table 1 - % Cross Sensitivity of Electrochemical Sensor
to Other Gases (SO = 100%)
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0% 10% 60% -60% 125% -125%
CO HCL HCN CL H S NO
22 2
NO
H
2
CH
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SENSOR OUTPUT
The sensor housing contains the circuitry for generating a 4 to 20 mA dc output signal, corresponding to
levels of SO from 0 to 100 PPM (optional 10 and 20 PPM). The 4 to 20 mA output is an un-calibrated
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signal. Therefore, calibration capabilities must be provided by a transmitter, controller, or display module,
to be used with the sensor.
INSTALLATION
CAUTION:
The electrochemical sensor contains semiconductor 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.
The following factors are important and should be considered for every installation :
1. Since sulphur dioxide is heavier than air, it will norm ally tend to settle near the floor or ground, unless it
is heated, mixed with other gases that are lighter than air, or prevented from settling by air movem ent.
2. Consider how rapidly the SO will diffuse into the air. Select a location for the sensor as close as practical
to an anticipated source.
3. Consider ventilation characteristics of the immediate area. Air movement will cause the gas to become
more concentrated in some areas than others. Always place the sensors where the most concentrated
accumulation of sulphur dioxide gas is anticipated. Also consider the fact that some ventilation systems
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do not operate continuously.
4. Locate the sensor away from potential sources of contam ination (dirt, etc.) if possible.
5. The sensor should be installed with the flame arrestor pointing down (refer to Figure 1) to prevent build-
up of contam inants and to ensure the device is weather resistant.
6. The sensor must be accessible for testing and calibration.
7. Exposure to excessive heat or vibration can cause premature failure of electronic devices and should be
avoided if possible. Shielding the device from intense sunlight will reduce solar heating and can increase
the life of the unit.
Remember, the finest detection system is of little value if the SO gas cannot readily come in contact
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with the sensor. First priority should be placing the sensor where the highest concentration of gas
is anticipated.
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.
Table 2 - Maximum Wiring Distances
Sensor to Controller/Transmitter
WIRE
SIZE
MAXIMUM SENSOR TO
CONTROLLER DISTANCE
(AW G) Feet Meters
18 5700 1750
16 9000 2800
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SENSOR WIRING
1. Determine the best mounting locations for the sensors.
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 element assembly 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 term inal 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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Figure 2 - Sensor Wiring
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START-UP PROCEDURE
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 transm itter, controller, or display module
manual.
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 SO detection system must be calibrated on a regularly scheduled 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 sulphur dioxide mixed with either air or nitrogen and should be
perform ed using 50% of full scale range calibration gas. i.e. ful scale range is 10 PPM calibrate with 5 PPM.
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Follow the "Calibration Procedure" outlined in the manual supplied with the transmitter, controller, or display
module used with the sensor.
If background SO is present, it may be necessary to purge the sensor with clean air (for the zero reading)
to ensure accurate calibration.
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MAINTENANCE
To ensure reliable protection, it is important to check and calibrate the SO detection system on a regularly
scheduled basis. The frequency of these checks will vary depending on conditions such as relative hum idity,
dirty or dusty environm ents, and concentration of SO .
Relative humidity is an important factor in the life expectancy of a sensor. Constant exposure to extremely 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 assem bly must be replaced. Spare sensing elem ent 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 SO2-20-24 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 contamination 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 assem bly contains an acid that occasionally can leak. If a leakage should occur, handle
the assembly carefully 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.
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TROUBLESHOOTING
Table 3 - 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.
Cannot zero on
calibration.
Cannot span on
calibration.
Low sensitivity. 1. Sensor may have been exposed to an extrem ely dry environment.
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.
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.
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.
Treat as outlined in the 'Maintenance' section.
2. Check for a dirt deposit on the flame arrestor. Clean if necessary.
Use a dust cover in dirty or dusty environm ents, or a rain shield
out-doors.
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APPENDIX A 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 m agnitude,
a spark will also be visible. This voltage is often more than enough to damage some electronic components.
Some devices can be damaged 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 immediate malfunction is realized. Often,
however, the symptoms are not im m ediately observed. Performance m ay be m arginal or even seem ingly
normal for an indefinite period of tim e, followed by a sudden and mysterious failure.
Damage caused by electrostatic discharge can be virtually eliminated if the equipment 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 M onitoring Inc. m odules that m ight 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 m odule, it is h ighly recomm ended 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 metal 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)
100 1.02 0.64 0.4 0.25 0.16 0.1 0.06
200 2.03 1.28 0.08 0.51 0.32 0.2 0.13
300 3.05 1.92 1.2 0.76 0.48 0.3 0.19
400 4.06 2.55 1.61 1.01 0.64 0.4 0.25
500 5.08 3.2 2.01 1.26 0.79 0.5 0.31
600 6.09 3.83 2.41 1.52 0.95 0.6 0.38
700 7.11 4.47 2.81 1.77 1.11 0.7 0.44
800 8.12 5.11 3.21 2.02 1.27 0.8 0.5
900 9.14 5.75 3.61 2.27 1.43 0.9 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
AWG #20 AWG #18 AWG #16 AWG #14 AWG #12 AWG #10 AWG #8
NOTE: RESISTANCE SHOWN IS ONE WAY. THIS FIGURE SHOULD BE DOUBLED WHEN DETERMINING CLOSED LOOP
RESISTANCE.
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Distributed By:
2721 Hopewell Place NE
Calgary, Alberta, Canada T1Y 7J7
Telephone: (403) 219-0688 Fax: (403) 219-0694
www.net-safety.com
E-mail: netsafe@net-safety.com
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