Tech Note
E lectrochemical Sensor Technology
For more than 50 years the electrochemical sensor has played an
important role in protecting lives and ensuring safety in the
workplace. The sensor was first used in the 1950’s to monitor
oxygen. Years later the technology was expanded and the sensor
became instrumental in detecting and monitoring toxic and
combustible gases. However, the biggest leap in innovation came in
the 1980’s. During this time the Occupational Safety and Health
Administration (OSHA) began drafting a proposal for a new safety
standard that would require the monitoring of toxic and combustible
gases in permit-required confined spaces. News of the proposal set
forth widespread activity in the development of new and better
electrochemical sensors: more compact, more robust, and with
improved selectivity and sensitivity for a wider range of toxic gases.
Then, in 1993 the proposed OSHA safety standard passed and
became 29 CFR 1910.146, mandating a higher level of worker safety
and further expanding the use of the electrochemical sensor.
In its simplest form, all electrochemical gas detection sensors include
a porous membrane and at least two electrodes: a sensing electrode,
and a counter electrode. During operation, target gas diffuses through
the gas permeable sensor membrane and onto the sensor electrode
surface producing an electrical current in proportion to the amount of
target gas reacted at the electrode.
Detcon’s electrochemical toxic gas sensors consist of three
electrodes embedded in an electrolyte solution and housed beneath a
diffusion membrane. Sensitivity to a specific target gas is made
possible by varying the composition of any combination of the sensor
components. The cells are diffusion limited by small capillary barriers
resulting in a long service life of up to three years or more. The
rugged sensors work well in demanding environments and at
elevated temperatures, able to detect toxic gases ranging from 01ppm up to 0-10,000ppm. Detcon manufactures four sensor
assemblies to monitor toxic gases using this electrochemical cell
technology: Model DM-100, Model DM-700, and MicroSafe® Models
DM-500/600. All are designed as easy-to-use field replaceable plugin sensors with intelligent electronics and a non-intrusive operator
interface using a hand-held magnet. Sensors are intuitive and feature
automatic calibration and comprehensive fault diagnostics.
D M-100 2 Wire Loop Powered Sensor
The Model DM-100 is a versatile low power gas
detection sensor that can be used with the Detcon
SmartWireless® product line, or purchased as a
separate stand-alone product. The sensors are two
wire 4-20mA loop powered with an intrinsically safe
design, and are packaged in an electro-polished 316
stainless steel vault with fully encapsulated
electronics and dual layer surge protection. It also has
a Modbus RS-485 signal output as a standard feature. Options
include an explosion-proof junction box with/without loop powered
LED display, a field replaceable transient protection circuit, an alarm
relay board, a current-to-Modbus™ converter, HART protocol, and a
wireless interface. The DM-100 is rated Class I, Division I, Groups A,
B, C, D.
D M-700 Environmentally Bulletproof
The Model DM-700 is a new generation of intelligent
sensor module designed specifically for harsh and
extreme locations. The sensor is equipped standard with
4-20mA and Modbus RS-485 outputs and is housed in an
intrinsically safe electro-polished 316 stainless steel vault
with fully encapsulated electronics and dual layer surge
protection. Sensor status is displayed on a built-in
alphanumeric LED display. Integration options include a
wireless interface module, Remote Alarm Module (RAM),
HART, Foundation Fieldbus, and Profibus. The DM-700 includes an
explosion-proof junction box and has a SIL2 rating assessed by
Exida. The DM-700 is Class I, Division I, Groups A, B, C, D.
DM-500/DM-600 MicroSafe
Detcon Models DM-500 and DM-600 MicroSafe
sensors come standard with a linear 4-20mA output.
The DM-600 includes an additional RS-485 serial
communications port and 3 alarm relays. Both the
DM-500IS and DM-600IS are packaged in
explosion-proof junction boxes with a glass lens
cover and are rated Class I, Division I, Groups B, C,
D. Both sensor types can be ordered with a remote
sensor and remote transmitter option.
For more detailed information on these and other Detcon products,
go to www.detcon.com or contact [email protected]