Electricity + Control March 2015

TEMPERATURE MEASUREMENT

ROUND UP

Reliable temperature measurement with new thermowell materials

Loop-powered BL 540 isolator for easiest 20 mA signal transmission

For galvanically isolated 1:1 transmission of 4..20 mA stand- ard signals, Knick provides the BL 540 isolator from its low-cost BasicLine series. By reliably decoupling the field and con- trol levels, the device prevents system malfunctions. At a low 1,7 V voltage drop, the device needs no auxiliary power supply but can be pow- ered through the loop – this results in the additional advan- tage of a much reduced wiring effort. The isolator features a 0,2% full scale accuracy. One and two-channel devices are avail- able in a 6 mm DIN rail hous- ing. BL 540 isolators are CE- compliant and UL-certified.

Taking temperature measurements ranging from 800°C to 1 700 °C there are particularly high demands on the measuring technology used. Many materials can only withstand the heat and other process con- ditions for a limited period. While some processes involve corrosive gases, other processes can be abrasive.This is exacerbated by turbulence and other extreme conditions, whichmake things more difficult for the component parts of a thermometer, particu- larly the thermowell. A combination of corrosion and abrasion is often the root cause of thermowell failure. At critical measuring points, measurements are either not taken continuously or the thermocouples must be replaced quite frequently.These measuring points increase the workload of the maintenance de- partments, drive up costs and often difficult to access. In recent years, materials research has provided us with many new materials, ranging from new metal alloys to robust ceramic substances. Endress+Hauser has examined and tested these new materials, and found it possible to use some to produce thermow- ells that withstand extreme process conditions far longer than previously experienced. Endress+Hauser has incorporated its research and testing results into the Omnigrad S TAF high-temperature sensor line. Given the extensive possibilities of combining the TAF11, TAF12S, TAF12D,TAF 12Tand TAF16 devices, the ideal thermocouple can be designed for every application. Enquiries: Benjamin Mlangeni.Tel. 011 262 8012 or email info@za.endress.com

See what it’s about VEGA has introduced their PLICSLED universal display module for all point level sensors.The module is compatible with all sensors in VEGA’s plics family with relay output. With this new displaymodule the switching status of a sensor can be read from a distance, even in strong sunlight. Since external wiring is unnecessary, Not-withstanding the attractive price scheme, the devices feature Knick’s characteristic high level of manufacturing quality and precision as well as com- plete galvanic isolation. BasicLine com-prises transducers for all major control cabinet requirements. Mecosa is the sole agent for Knick ElektronischeMessgeräte in SouthernAfrica. Enquiries:Tel. 011 257-6100 or email measure@mecosa.co.za Knick pro-vides a three-year warranty for the devices. Strictly concentrating on basic functions, leaving all extras aside, Knick has tailored BasicLine devices to mechanical engineering companies that need precise and reliable yet cost- optimized isolators for large-scale applications.

the time needed for installation is reduced to a minimum. Power is supplied via the relay electronics. The second re- lay output is used to control the switching status display.

Depending on the module version, the switching status is displayed in the colour combination red- green or yellow-green. PLICSLED is installed

directly inside the plics sensor housing giving it protection from dust and water. The display module can be ordered directly with the sensor or, alternatively, as a separate unit for retrofitting.

Enquiries: Chantal Groom. Tel. 011 795 3249 or email chantal.groom@vega.com.

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