Novatech Measurements Ltd. - PRODUCT NEWS
   

New Load Cells operate up to 250ºC. Novatech are delighted to announce that we can now offer Load Cells that maintain their very high accuracy figures right up to an incredible 250°C ! This new technology opens up a whole new area of applications that require higher than normal temperatures eg - hot presses, engine test beds, chemical/food/pharmaceutical processes, Hi Temp research etc. Technical Overview All loadcells have output spans that change with temperature. This causes significant measurement errors particularly if the loadcell is required to operate over a wide temperature range. The currently used method for compensating for this error in strain gauged loadcells is to use nickel or Balco foil resistors in series with the sensor excitation connections. The method is limited in accuracy by the non-linearity of the resistance change of the foil resistors with temperature. This non-linearity increases at temperatures above 100°C and foil resistors are not suitable for use at temperatures above 200°C. Novatech's new invention compensates for loadcell output span changes with temperature by using passive temperature sensitive elements in the bridge circuit. The temperature coefficient of the temperature sensitive elements is adjusted to be the inverse of the sensor's uncompensated span change with temperature. Accurate linear compensation can be achieved over a temperature range of -50 to 250°C. This method is inherently more linear than traditional methods that employ nickel or Balco resistors in series with the sensor excitation connections, giving performance specification several times better on span (typically 0.0025% output/°C) than most other load cells currently available for high temperature use. With additional trimming over a range of temperatures of particular interest we would expect to achieve <0.001% output/°C. Novatech has an international patent application pending for this novel approach to high temperature modulus compensation, currently available on 70% of Novatech products. We are currently capable of calibrating up to two tonnes, but higher calibration levels will be available soon. _______________________________________________ April 2002
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