Smart sensing in the face of adversity
NEW PRODUCTS and INNOVATIONS Smart sensing in the face of adversity May 2011
Mark Rowland, Engineering Manager of Trolex explains the development of the company's latest intelligent gas detector.
Taking its lead from the recent Sentro 8 innovation, Sentro 1 employs similar new technology for stand-alone single gas safety monitoring in applications where robust equipment is essential in these adverse environments.
Sentro 1 uses plug-in eModules for stand-alone single gas monitoring

Sentro 1 uses plug-in eModules for stand-alone single gas monitoring

The heart of Sentro 1 lies in the intelligent plug-in gas sensing modules. Trolex has designed these new 'eModules' to store all the necessary data about its type identification, sensing range and specific calibration. This data is automatically recognised by Sentro when the eModule is plugged in. There are some 4,000 points of time and date stamped data logging which can be reviewed on the display or downloaded to a computer through the RS485 data link. The service history of the module and the condition of the sensing elements are also recorded.
These eModules are pre-calibrated with a standardised output signal for convenient replacement and servicing. The new technology allows easy plugging and unplugging of modules, each containing a wealth of information and this simple process provides for ease of maintenance and low downtime.
The new Sentro 1 gas detector allows for the insertion of a range of eModules. There are electrochemical cells for monitoring toxic gases. These combine good sensitivity at low gas concentrations with high range capability and excellent stability.
These eModules are available for monitoring carbon monoxide, hydrogen sulphide, sulphur dioxide, nitrogen dioxide, chlorine, oxygen or hydrogen.
Quick change-over of eModules and fast re-calibration are special features

Quick change-over of eModules and fast re-calibration are special features

There is a poison resistant catalytic sensor to detect flammable gases in particular, methane. This has good sensitivity at low levels of concentration. The relatively large mass of the sensing element ensures a long and reliable operating life with exceptional stability even in conditions of high vibration. Completing the range are infrared Sentro eModules for monitoring environmental concentrations of either carbon dioxide or methane gases. These sensors have consistent sensing accuracy with superior long-term stability, so minimising calibration and maintenance.
Convenient and rapid calibration
The simplicity of the change out of eModules within the new Sentro 1 Gas Detector means that calibration is swift and easy. Whereas in the past, specialist technicians would need to be called for complex calibration procedures leaving the equipment dangerously out of service, Sentro 1 allows for a quick change-over of modules or re-calibration almost instantly. The system allows for two methods of calibration; this can either be a straightforward module replacement; or alternatively there are internal calibration buttons to be used in conjunction with a bayonet fixed gas hood.
Sentro 1 features a high strength moulded housing with dual wall construction for maximum impact strength.
It is sealed against dust and moisture to IP65 and is also EMC protected. Inside there are secure easy connections with large terminals and a spring loaded wire clamping plate for safe and vibration secure connections.
Monitoring eModules

Monitoring eModules

It is also able to accept simple cable terminations and there is an M20 threaded cable entry plus a hinged segregation cover for added operator safety. Outside there is a large LCD readout by way of a high brightness, dot matrix display providing clear information with direct on-screen instructions and diagnostic data.
Overall, the Sentro 1 housing has been designed with maintenance in mind. Whatever service needs to be carried out, it is simple and quick and can be easily maintained by plant engineers for a high level of plant safety. Certified intrinsically safe to ATEX standards, Sentro 1 is available as 12V for Group I applications or 24V for Group II or General Purpose Applications. There is a range of output signal versions available: 0.4…2V, 4…20mA and 5…15Hz, dual relay contacts or RS485. Several options can be specified including built-in audio visual alarms that can be selected to operate at two adjustable alarm setpoints.

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