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.
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April 2002
