Oldham 700 TP Series, Instruction Manual

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OLCT 700/710 TP
OLCT 700/710 TP Instruction Manual Rev. C.1 Page 1 of 45
1. Introduction
1.1 Description
Oldham OLCT 700 TP hydrogen sulfide gas transmitters are
non-intrusive “Smart” detectors designed to detect and monitor
H
2
S in air. Ranges of detection are 0-20ppm, 0-50ppm, 0-
100ppm, and 0-200ppm. The detector features an LED display
of current reading, fault and calibration status. The detector is
equipped with standard analog 4-20mA and Modbus™ RS-485
outputs. A primary feature of the detector is its method of
automatic calibration, which guides the user through each step
via fully scripted instructions displayed on the LED display.
The microprocessor-supervised electronics are packaged in an
encapsulated module and housed in an explosion proof casting,
called the ITM (Intelligent Transmitter Module). The ITM
includes a four character alpha/numeric LED used to display
detector readings, and the detector’s menu driven features when
the hand-held programming magnet is used.
The OLCT 710 is made of an OLCT 700 attached to a flameproof junction that includes terminal blocks
and an optional surge protection board. The complete assembly is flameproof certified « Ex d » and carries
ATEX approval (see section 2.1- ATEX Operational Guidelines for Safe Use).
The OLCT 700 is flameproof certified and carries ATEX approval. The OLCT 700 shall be attached to an
increased safety certified junction box when used in an ATEX zone (see section 2.1- ATEX Operational
Guidelines for Safe Use).
Solid State H
2
S Sensor Technology
The sensor technology is a patented solid-state mixed metal oxide semiconductor.
The sensor consists of two thin films, a temperature sensitive heater film, and a
hydrogen sulfide sensitive sensor film. Both films are deposited on a silicon
microchip by vacuum deposition. The heater film elevates the operating
temperature of the sensor film to a level where a good sensitivity and response to
hydrogen sulfide is achieved. The sensor film is a proprietary mixed metal oxide
that shows an extremely stable and dynamic response to hydrogen sulfide gas.
Range of sensitivity is from parts per billion to percent by volume. The rugged
sensor is capable of maintaining its operating characteristics for periods of up to 7-
10 years in most industrial environments and as such, is supported by a 5-year
warranty.
Principle of Operation
Method of detection is by diffusion/adsorption. Air and H
2
S diffuse through a sintered stainless steel filter
(flame arrestor) and contact the heated surface of the metal oxide sensor film. As hydrogen sulfide gas
molecules react with oxygen ions on the film, there is a decrease in electrical resistance proportional to the
gas concentration. The heater film elevates the temperature of the sensor film creating convection and
promoting a quick response to changing gas concentrations. Electronically, the heater film is used to
maintain a constant temperature of the sensor film enhancing stability and repeatability. The sensor
response is reversible and results in continuous monitoring of ambient air conditions.
OLCT 710 OLCT 700