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Sometimes the temperature sensors are design with offset set to 0 for room temperature. But when it is connected to system the application / controller reads some reading instead of 0. So when ever there is change in temperature the initial offset gets added up at large temperature change the result is wiery or wrong.
calibration is the process of comparing something to a known standard. For temperature sensor, though it may say it is accurate, you must test it to find its offset. example is, test the sensor against something that is constant, like boiling water, which is true always at 100 deg celcius. any deviation from that is the offset, which must be taken into account on the design and calculation. Hope this helps
It is a three-terminal device with voltage output that can connect directly to the OWL2c analog inputs.
It has a high level linear voltage output,10mV per 'F or 10mV per 'C respectively.
The output voltage is zero at zero degrees Fahrentheit (TF, LM34), or zero degrees Celsius (TC, LM35). Compare that offset to other sensors which are offset relative to zero Kelvin or are nonlinear.
The calibration is accurate right from the factory. The highest grade sensors we use in the TF and TC probes is accurate to within +/- 1 'F (+/- 0.5 'C).
EME Systems provides additional calibration at one or two points to reduce the error to +/- 0.25 'F (+/- 0.125'C) over the biological temperature range:
The operating temperature for the TF probe is 0.0 to 230 'F (-17 'C to +110 'C), and for the TC probe it is 0'C to +110'C for the TC probe.
The output from these sensors connects directly to the OWL2c A/D converter, and gives a resolution of 1/8'F or 1/8'C.
EME Systems has developed a three-dimensional circuit board that turns the LM34 or LM35 into robust and stable cable-mounted probe, good for 100 feet (30 meters) or more extension from the measuring system.
We usually recommend using the TF probe to cover the biological temperature range due to fact that the range that extends below freezing. It is easy to convert to Celsius in software if necessary. (Celsius=Farenheit -32 * 5/9)
gosub ADread ' result in millivolts
degF=result ' degree F * 10, 1/8 degree resolution
degC=degF*5/9-178 ' convert to degrees Celsius * 10
debug REP "-"\degC.bit15,DEC abs degC,".",SDEC1 degC
There are other ways to do the computation. The subtraction is done after the multiplication and division sot that it will handle temperatures down to -17.8 Celsius. (The stamp does not divide negative numbers properly.) The DEBUG statement prints out the value, and it is complicated by the need to display negative values for Celsius, with one decimal point and the tenths.
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