# Temperature measurement using PT100

Objective

Record the temperature of a liquid by using a Platinum Resistance Thermometer. Resistance of a PT100 element is related to the temperature by the equation , where and .

Procedure

- Enter the Gain, Offset error and the Current from CCS

- Select the temperature range and time intervals

- Select the required parameters and press START

Discussion

Cooling curve of water is shown in figure

To measure the resistance of the PT100 element, we connect it from the CCS to ground and measure the voltage across it. The actual current of CCS should be measured using an ammeter or by measuring the voltage frop across an known resistor. The input to A3 is amplified 11 times by connecting resistor from Rg to Ground.

The resistance of PT100 is at . It changes nearly , changing the voltage by . The 12 bit ADC output changes by 1 LSB for change in input voltage, hence any temperature change less than 3 degrees will not be detected. Use an external non-inverting amplifier to increase the resolution. The gain of the amplifier should be such that the maximum temperature measured should give an output less than 3.3 volts. Change the gain field entry accordingly.