OTIS OI-675 Manuel utilisateur
Model OI-675 Electrochemical
Sensor Assembly
Operation Manual
Revision 1.4
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Product Overview
The Otis Instruments, Inc. Model OI-675 Electrochemical Sensor Assembly is a ersatile system with
the ability to detect of a ariety of gases.
The OI-675 Electrochemical Sensor Assembly's key feature is non-intrusi e calibration. With all
adjustments made at the sensor assembly, one-man non-intrusi e calibration is quick, easy, and allows
the de ice to remain Class I, Di ision 1, Groups A, B, C and D certified while in the field. Non-
intrusi e calibration is made possible by using an Otis Instruments, Inc. distributed magnet to acti ate
the MENU, ADD and SUB buttons.
The OI-675 incorporates any “4” Series Electrochemical Sensor and the OI-352 two-wire loop (4 to
20mA output) Amplifier Card.
An extended life-expectancy, paired with the ability to withstand extreme climatic conditions and harsh
en ironments, make the OI-675 Electrochemical Sensor Assembly a flexible and dependable safety
tool for gas detection.
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Table of Contents
Product Overview.............................................................................................................3
Introduction......................................................................................................................6
Modified Terminal Position.............................................................................................7
4-20mA urrent Loop Introduction...............................................................................8
Overview...............................................................................................................................................8
Calculations..........................................................................................................................................8
Measuring Current..............................................................................................................................9
Warnings.........................................................................................................................10
omplete System Diagrams...........................................................................................11
OI-675 Complete System w/ ainguard............................................................................................11
OI-675 Complete System w/out ainguard.......................................................................................12
OI-352 Front Panel (Amplifier Card)...............................................................................................13
Wiring onfigurations...................................................................................................14
Sensor Configuration ........................................................................................................................14
Power Supply Configuration ............................................................................................................16
Power On............................................................................................................................................18
alibration .....................................................................................................................19
Change/Check Null............................................................................................................................20
Setting Calibration ............................................................................................................................21
Sensor Replacement.......................................................................................................24
Specifications..................................................................................................................29
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Introduction
This document is an Operation Manual containing diagrams and step-by-step instruction for proper
operation of the Otis Instruments, Inc. Model OI-675 Electrochemical Sensor Assembly. This
document should be read before initial operation of the product.
Should a question arise during the use of the product, this document will ser e as a first reference for
consultation. If further questions arise, or if the de ice is not working properly, please contact the sales
representati e of this product.
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Modified Terminal Position
New OI-675 Sensor Assemblies are now assembled with the terminal block on the back side (Back
Panel) of the Front Panel. Please use the following diagrams as a reference for performing
maintenance on a “new” OI-675.
1. Remo e the Amplifier Card from the enclosure and turn o er so that the Back Panel is isible.
2. Bring the conductor cables from the controller/monitor to the Back Panel of the Amplifier Card
using the proper 3/4” NPT cable gland.
3. Connect the conductor cables to the terminal marked “Input”.
4. Verify that the 4-20mA (signal) and V++ (power) match the controller connections.
5. Replace the Amplifier Card back in the enclosure by matching each Back Panel mounting post
to its corresponding eyelet (inside the enclosure).
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4-20mA Current Loop Introduction
This is just a brief o er iew of 4-20mA—this o er iew should not be considered a complete reference
for proper implementation or use. Prior knowledge of industry standards pertaining to 4-20mA
specifically, and other aspects of electronics, are assumed to be known by the technician. For proper
connection to a monitor or PLC, refer to the manufacturer's specific manual or instructions for that
particular piece of hardware.
Overview
4-20mA ("four to twenty”), is an analog electrical transmission standard used by Otis Instruments for
some of its ambient gas sensors and monitors. The signal is a current loop where 4mA represents zero
percent signal, and 20mA represents 100 percent signal (full scale of the sensor assembly). The
relationship between the current loop and the gas alue is linear.
The 4mA allows the recei ing monitor/PLC to distinguish between a zero signal, a broken wire, or a
dead instrument. Benefits of 4-20mA con ention are that it is: an industry standard, low-cost to
implement, can reject some forms of electrical noise, and the signal does not change alue around the
“loop” (as apposed to a oltage). Only one current le el can be present at any time; each de ice which
operates ia 4-20mA must to wired directly to the monitoring de ice.
Calculations
I4−20=
16⋅value
scale
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I4−20
: current of loop, measured in mA
alue : PPM or %, of gas concentration
scale : full scale of sensor (see below for usual ranges)
Table – Gas Sensor Details
-more-
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Tar et Gas Ran e Temp.
H2S = Hydrogen Sulphide 0-100 ppm -20 to 50C
O2 = Oxygen 0-25 % -30 to 55C
SO2 = Sulfur Dioxide 0-20 ppm -20 to 50C
CL2 = Chlorine 0-10 ppm -20 to 50C
H2 = Hydrogen 0- % -20 to 0C
NH3 = Ammonia 0-100 ppm - 0 to 0C
CO = Carbon Monoxide 0-999 ppm -20 to 50C
F2 = Florine 0-1 ppm -10 to 0C
HF = Hydrogen Fluoride 0-10 ppm -10 to 0C
H2S-2 = Hydrogen Sulphide 0-100 ppm - 0 to 50C
(extended temp)
Calculations cont...
Actual ranges may ary with our product. If unsure, confirm with the actual gas sensor assembly
distributor, Otis Instruments sales representati e, or call the main Otis Instruments office for more
details.
Measuring Current
If the alue measured is 0mA, then: the loop wires are broken, the sensor assembly is not powered up,
the sensor assembly is malfunctioning, or the monitor is malfunctioning. A DMM (digital multi meter)
or Current Meter may be used to test a 4-20mA signal. Place the DMM or Current Meter in line with
the loop and measure current. The DMM/Current Meter may be used in conjunction with the normal
monitoring de ice.
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Warnin s
The Otis Instruments OI-675 Electrochemical Sensor Assembly is Class I Di ision 1
Certified. The assembly is able to maintain its certification at all times while in the field,
simply by using the non-intrusi e calibration method which requires the use of an Otis
Instruments, Inc. distributed magnet. Howe er, if the Moore lid is remo ed, for whate er
reason, the OI-675 Electrochemical Sensor Assembly's certification is no longer alid.
To a oid in alidating the certification, complete all wiring configurations BEFORE putting
the OI-675 Electrochemical Sensor Assembly in the field. Once in the field, always use the
Otis Instruments, Inc. distributed magnet to ensure non-intrusi e calibration.
Strong magnetic fields may interfere with the non-intrusi e magnetic switches. A strong
magnetic field may momentarily acti e a switch, or permanently disable the switch to the
“on” or “off” position.
Do not co er the hole in the calibration cup, as this will cause the calibration to be
inaccurate.
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Table des matières
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