Note
Some analog inputs have a low input resistance. The internal input resistance is connected in parallel to
the input.
Example: Measuring a motor temperature using a PT1000 temperature sensor
According to the PT1000 resistance table (provided, for example, from your sensor’s datasheet) the
resistance of the sensor should be 1000 Ω for 0° C and 1385 Ω for 100° C.
The reference voltage is 5 V, and the ADC resolution is 12 bits, so the ADC output value would be 4095
for full scale input voltage.
The image below depicts a schematic of input circuits. The ADC will measure the input voltage which is
proportional to the resistance.
The sensor resistance and the input resistance are in parallel which means: R =
If the temperature sensor is used on the single-ended analog input of Circulo then R = R because R >> R
.
The input voltage is = 5 V ·
To evaluate the accuracy, the amount of ticks for the measured temperature range needs to be considered:
Temperature range / Amount of ticks for the temperature range = Temperature measured / tick
total
s total i
s
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