Usually the temperature measurement is carried out by using thermocouples and RTDs. The conventional method of recording the measured temperature is very time consuming due to the non-linear characteristics of the sensors and may introduce human errors. Hence digital thermometers are developed to obtain the direct display of the temperature.
Block Diagram of Digital Thermometer
Fig. 1: Block Diagram of Digital Thermometer
The block diagram of a digital thermometer is as shown in Fig. 1. The linearizer used in digital thermometers is very important block. Using microprocessor based linearization technique, same unit can be used for different types of thermocouples. Fig. 1 shows the block diagram a digital thermometer.
Construction of Digital Thermometer
It consists of Temperature sensor like thermocouple. The compensating network to provide the reference temperature to the thermocouple. Signal conditioner like amplifier. Analog to digital converter (ADC), and Electronic display unit for direct display of the temperature.
Working of Digital Thermometer
The thermocouple senses the temperature and produces proportional thermoelectric e.m.f. (voltage) in response to the changes in temperature. The compensating network provides the reference point for the thermocouple by producing a compensating voltage proportional to the reference temperature. The output of the thermocouple is further amplified by the amplifier. This amplified analog signal is fed as input to the ADC (Analog to digital Converter) which converts it into an equivalent digital form. The digital voltage from analog to digital Converter is linearized by the linearizing system and then used to drive the electronic display unit to give the digital display corresponding to the measured temperature.
Advantages of Digital Thermometer
- The temperature readout is simple.
- High accuracy.
- Small in size