Product category:
Gas monitoring and analysis
News Release from: Siemens Automation and Drives | Subject: Sigrist VisGuard
Edited by the Processingtalk Editorial
Team on 31 October 2005
Highly reliable dust monitoring solution
Companies that rely on dust concentration detection to monitor dust or exhaust gas limits or to control ventilation systems can now have a highly reliable solution from Siemens
Companies that rely on dust concentration detection to monitor dust or exhaust gas limits or to control ventilation systems can now turn to Siemens Automation and Drives - Process Instrumentation and Analytics for a highly reliable solution The Sigrist VisGuard measures the scattered light intensity of a sample drawn into the instrument using a dual-beam measuring method
This article was originally published on Processingtalk on 10 Apr 2006 at 8.00am (UK)
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It determines the relation between the light scattered at a 30 degree angle and the directly transmitted light.
This system eliminates the effects of any light source fluctuations as well as ageing or temperature effects.
The system works when a light beam is passed through air or gas containing dust or soot particles or finely dispersed droplets of liquid (eg aerosol, mist) and the particles or droplets scatter the light.
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Measurement of the scattered light intensity therefore provides an indication of the concentration of the dust particles or aerosol in the sample.
The air is extracted through a blower and carried through the flow cell.
This configuration permits extremely simple installation without time-consuming alignment or adjustment, reliable checking and correction of the zero and reference points without ambient air effects.
Users have the flexibility to carry out measurement either on the spot or remotely with extraction lengths up to 500m.
In the in-situ version the blower is integrated in the sensor.
For the extractive arrangement, separate fans are used because more power is required.
An optional heater at the sample inlet effectively eliminates any troublesome mist effects.
The blower also feeds filtered purge air to the flow cell, thus enveloping the sample in a protective shroud of clean purge air.
This keeps the optics clean and minimizes drift caused by fouling.
Extractive sampling also allows the possibility of carrying extraction pipes from up to 8 sampling pipes via a valve unit to a simple sensor.
With the multichannel control unit SIBUS, the continuous sample flows from the different extraction points are fed cyclically to the VisGuard.
In this case the maximum extraction length is 200m.
Calibration of the Sigrist VisGuard is carried out at the factory based on PLA (polystyrene-latex aerosol) as the defined medium.
If necessary, an application-specific calibration can be carried out in mg/m3.
For the annual calibration check, a checking rod is available that permits correction of the instrument in a matter of seconds.
If required, the zero point can be checked at the same time by attaching a zero-air filter.
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