MODEL: H S-100ppm. Optional 50ppm, 20ppm and 10ppm
2
Available in: 24Vdc Version / 12Vdc Version / 10 - 32Vdc
ASSEMBLY CONSISTS OF:
XP-H S housing (supersedes PE-EX-H S-S)
ST1200-XXX sensor (supersedes PE1200-XX-XXX)
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JB2 junction box
CB2 connector board
ELECTROCHEMICAL H S
2
DETECTOR
(used with ST1200 H S
2
Sensor)
Part Number: MAN-0010-00 Rev 1
Copyright © 2002 Net Safety Monitoring Inc.
Printed in Canada
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 honoured by Net Safety Monitoring Inc.
Contact Net Safety Monitoring Inc or an authorized distributor for details.
Table of Contents
DESCRIPTION ............................................................... 1
FEATURES .................................................................. 1
SPECIFICATIONS ............................................................ 1
Figure 1 - H S Detector Assembly .......................................... 2
SENSOR OPERATION ......................................................... 3
SENSING ELEMENT .................................................... 3
Table 1 - Cross Sensitivity of Electrochemical Sensor to 100 ppm Concentrations .... 3
SENSOR OUTPUT ..................................................... 3
I NSTALL ATION ............................................................... 3
DETECTOR POSITIONING ............................................... 3
WIRING REQUIREMENTS ............................................... 4
Table 2 - Maximum Wiring Distances Sensor to Controller/Transmitter ............. 4
SENSOR WIRING ...................................................... 4
Figure 2 - Sensor Wiring ................................................. 6
START-UP PROCEDURE ...................................................... 7
CALIBRA TION ............................................................... 7
MAINTENANCE .............................................................. 7
SENSING ELEMENT REPLACEMENT ...................................... 8
TROUBL ESHOOTING ......................................................... 9
Table 3 - Troubleshooting Guide ........................................... 9
SPARE PARTS ............................................................... 9
Appendix A
Net Safety Monitoring Inc. Electrostatic Sensitive Device Handling Procedure . . . . . . . . . . . . . . . i
2
Appendix B
Wire Resistance In Ohms ........................................................ii
DESCRIPTION
The Net Safety Monitoring Inc. H S-XXX-XX electrochemical Hydrogen Sulfide (H S) gas detector
consists of an explosion-proof enclosure, electronic circuitry and an electrochemical H S sensing
element. This H S sensor provides continuous monitoring of hydrogen sulphide (H S)
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concentrations in the range of 0 to 100, 50, 20 or 10 parts per million (ppm). The detector can be
used with one of the Net Safety Monitoring Inc. Uni-Trol™ Controllers or with other devices that
are capable of monitoring a 4 to 20 mA dc input and provide for calibration of the incoming signal.
The explosion-proof detector is CSA certified for use in hazardous locations.
FEATURES
< Electrochem ical sensor for increased accuracy, repeata bility and reliability.
< High specificity to H S reduces the chance of false alarms caused by other
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gases.
< Temperature compensation to ensure consistent performance over the entire
operating temperature range.
< Self-contained transmitter circuitry permits use without a separate controller.
< Explosion-proof housing.
< EMI/RFI protected.
SPECIFICATIONS
< Operating Range:
0 to 100 ppm
Optional 0-50ppm, 0-20ppm and 0-10 ppm models available.
< Response Time:
20% full range within 12 seconds.
50% full range within 30 seconds
Note: When H S concentration equal to full scale is applied.
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< 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 4 years.
< Operating Voltage:
10 to 32Vdc. 24Vdc nom inal.
< Temperature Range:
Operation: -40ºC to +50ºC (-40ºF to +122ºF)
Recommended Storage: 0ºC to +20ºC (+32ºF to +68ºF)
< Humidity Range:
15 to 90% RH, non-condensing.
< Certification:
CSA certified, Class 1, Division 1, Groups C & D.
< Enclosure Material:
- 1 -
Anodized alum inum or optional stainless steel.
< Dimensions:
Refer to Figure 1
< Shipping Weight (Approximate):
Housing: 2.5 pounds (1.1 kilograms)
Sensing element: 0.2 pounds (0.1 kilograms)
Figure 1 - H S Detector Assembly
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- 2 -
SENSOR OPERATION
SENSING ELEMENT
The electrochemical sensing element uses capillary diffusion barrier technology for detecting the
presence of hydrogen sulphide gas. The electrochemical sensing elem ent provides improved
accuracy, reliability and extended calibration intervals when compared to ordinary solid-state type
sensors.
The response of the sensing element is highly specific to H S. Since m any com m only
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encountered gases have little, if any, effect on the electrical response of the sensor, false
indications caused by the presence of these gases is greatly reduced. Below is a list of
responses of the H S electrochemical sensor to 100 ppm concentrations of other gases.
2
0ppm < 1ppm <15ppm <-30ppm -20ppm
HCN CO SO NO Cl
CH NO H
24 2
H
2
222
HCl
Table 1 - Cross Sensitivity of Electrochemical Sensor to 100 ppm Concentrations
SENSOR OUTPUT
The sensor housing contains circuitry for generating a 4 to 20 mA dc output signal corresponding
to levels of H S from 0 to 100 ppm (optional 0-50ppm, 0-20ppm and 0-10ppm models available by
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special order). The 4 to 20 mA output is an un-calibrated signal, therefore, calibration capabilities
must be provided by a transmitter, controller or display module to be used with the sensor.
The sensor may be calibrated externally by removing it from the housing and placing it in a
calibration appliance for adjustment. Consult your distributor.
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
num ber of detectors needed and the best detector location.
NOTE
The finest detection system is of little value if the H S gas cannot readily come in
contact with the sensor. First priority should be placing the sensor where the
highest concentration of gas is anticipated.
- 3 -
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The following factors are important and should be considered for every installation:
< Since hydrogen sulfide is heavier than air, it will 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 movement.
< Consider how rapidly the H S will diffuse into the air. Select a location for the
2
sensor as close as practical to an anticipated source.
< Consider ventilation characteristics of the immediate area. Air movement will
cause the gas to become m ore concentrated in som e areas than others. Always
place the sensors where the most concentrated accumulation of hydrogen sulfide
gas is anticipated. Also consider the fact that some ventilation systems do not
operate continuously.
< Locate the sensor away from potential sources of contamination (dirt, etc.) if
possible.
< The sensor should be installed with the flame arrestor pointing down (refer to
Figure 1) to prevent build-up of contaminants and enhance weather resistance.
< The sensor must be accessible for testing and calibration.
< 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 m ay increase the life of the unit.
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 used. See table below for the
maximum wiring distance 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 2 - Maximum Wiring Distances Sensor to Controller/Transmitter
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
- 4 -
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. Thread the sensor housing into the junction box. The sensor should be tight to ensure an
explosion proof housing, but do not over tighten. CSA requires 5 full threads engaged.
NOTE
Coat sensor threads with an appropriate grease to ease installation. Lubricate the
junction box cover threads and O-Ring to ensure a water-tight enclosure.
8. Connect the sensor wires to the sensor terminals 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.
Wiring Code: Red lead: +24Vdc, (+12Vdc version dependant)
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.
- 5 -
Figure 2 - Sensor Wiring
- 6 -
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 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.
Calibration must be performed when:
< a new system is initially put into service;
< the sensing element is replaced, or;
< a transmitter or controller used with the sensor is replaced.
IMPORTANT
Do not use am pules and dilution bottles for calibration. Use certified bottled gas.
To ensure adequate protection, the H S detection system must be calibrated on a
regularly scheduled basis.
2
It is recommended that the sensor be calibrated one hour after power-up and calibration should
be checked every 30 days thereafter and re-calibrated if necessary. Consult the controller manual
for proper calibration procedure.
It is acceptable to use ampules and dilution bottles for checking sensor response but not for
calibration. Use bottled gas for calibration. Bottled gas has a limite d shelf life. Be sure it is
fresh.
MAINTENANCE
To ensure reliable protection it is important to check and calibrate the H S 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 environments and exposure to H S.
Relative hum idity is an im portant 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 more humid environments in order to rehydrate. 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. Do not freeze. If this does not
restore normal response the sensor must be replaced.
A rain shield/dust cover such as the CCS-1 should be used when the sensor may be exposed to
rain, water splash or dust. Be aware that ice and snow build-up could block gas from entering the
sensor.
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- 7 -
SENSING ELEMENT REPLACEMENT
The sensing element assembly is not intended to be repaired. When calibration can no longer be
performed properly, the assembly m ust be replaced. Spare sensing element assem blies should
be kept on-hand for field replacem ent.
Care should be taken in storing spare sensing elements. For maximum protection against
contamination and deterioration, sensing elements 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 5/C and 20/C (40/F and 68/F) and a relative
humidity between 15 and 90 percent. A typical refrigerator is a good place for storage. Do not
freeze. Storage time should be limited to 6 months or less.
The area must be de-classified or power to the detector must be removed prior to replacing the
sensing element in a hazardous area.
To replace the sensing element in the H S-XXX-XX detector:
2
1. Rem ove power from the detector.
2. Remove the cap from the detector housing.
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 detector 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 contains an acid that 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.
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TROUBLESHOOTING
PROBLEM RECOMMENDATION
No 4 - 20 mA
output
Fluctuating
current output
Cannot zero
during
calibration
Cannot span
during
calibration
Low sensitivity 1. Sensor may have been exposed to an extremely dry environment.
1. Check the 10 to 32 power input.
2. Check that the green LED on the sensor circuit board is on. If off,
check wiring, especially the polarity. Also check for proper
connection at the sensor terminals in the junction box.
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.
2. Check current output from sensor by opening the loop or checking
voltage across series resistor on terminal board. If output from
sensor is too low (approx. 2.8mA or less), replace sensor.
1. If the current output from the sensor is low the sensor may have
been exposed to an extremely dry environment. Refer to
'Maintenance' section to rehydrate.
2. If output from sensor is too low replace sensor.
Refer to 'Maintenance' section.
2. Check for a dirt deposit or other obstruction of the flame arrestor.
Clean if necessary. Use a rain shield/dust cover if necessary.
Table 3 - Troubleshooting Guide
SPARE PARTS
XP-H2S housing
ST1200-100ppm sensor
ST1200-50ppm sensor
ST1200-20ppm sensor
ST1200-10ppm sensor
JB2 junction box
CB2 connector board
- 9 -
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. 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 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 eliminated 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 pack aged. Foam packaging blocks are also treated with an anti-static agent. If it should
ever become necessary to return the m odule, 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, tak ing 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 E1A standard 471
i
Appendix B
Wire Resistance In Ohms
DISTAN
CE
(FEET)
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
AWG #20 AWG #18 AWG #16 AWG #14 AWG #12 AWG #10 AWG #8
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.
ii
2721 Hopewell Place NE
Calgary, Alberta, Canada, T1Y 7J7
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