SCCD MINI PROJECT SIGNAL CONDITIONING OF THERMISTOR|MU| Instrumentation Engineering-signal conditioning circuit design
Complete Project with circuit diagram and project report:
Title: SIGNAL CONDITIONING OF THERMISTOR USING OP-AMP 741 AS INSTRUMENTATION AMPLIFIER.
A thermistor change in electrical resistance due to a corresponding temperature change is evident whether the thermistor’s body temperature is changes as result of conduction or radiation from the surrounding environment or due to self heating brought about by power dissipation within the device.
As the temperature around the thermistor changes it changes its resistance and we get variable voltage because of Wheatstone bridge arrangement. In signal conditioning stage we use instrumentation amplifier to bring signal to vary in the voltage range of 0-5 volt dc.
To run this 3 op-amp base instrumentation amplifier circuit you need a dual power supply having output voltage +15v 0 -15v
and it can be designed by using fixed regulator IC LM7815 and LM 7915. we will discuss power supply design in another project.
In industry, the actual process of control panel is situated far away. So output of sensor is sends to the control panel. Due to atmospheric condition, signal at the control panel will not the desired signal.
Therefore this type of signal conditioning of thermistor using instrumentation amplifier can be used in industry.
TYPES OF THERMISTOR:-
NTC (Negative Temperature Coefficient)
It implies that the resistance of thermistor decreases with increases in its
temperature. These thermistors can detect changes in temperature, which could not be observed with RTD’s or Thermocouple circuits. NTC type thermistors mostly used in industry. Resistance of thermistor is used in industry is 2.2 k Q. for temperature 30°C. It’s cost near about Rs. 10-15
*Accuracy :± 1
*Resolution: 0.01 ºC
*Thermister Constant: 4000ºK