Lab strikes again!

A few weeks ago, we have been given one type of sensor for every group. Different group will be given a different type of sensor. As for my group, we have received a THERMISTOR sensor. Generally thermistor can be classified into two types which are the PTC (Positive Temperature Coefficient) and the other one is NTC (Negative Temperature Coefficient)

As for our Sensor's Lab Practical, we just being given a sensor and we have to design and construct the NTC sensor together with the Op-Amp circuit, and ADC circuit as well.

The Challenges:

Design:

Designing the sensor circuit is too mainstream. Seriously. NTC will gives -ve volts output as the result, so we have to use the Inverting Op-Amp to invert the -ve volts output to +ve volts. As what we have learnt in the previous semesters in Electronics Subject (chapter Operational Amplifier), this is the time for us to apply it in this lab practical. So we used the 741 Op-Amp to covert -ve output to the +ve output.

ADC input should less than 5volts:

Here's come with another problem. An ADC (Analog to Digital Converter) input limits is 5volts or even less. If the input exceeds than 5volts, the circuit will be 'burnt'. In this lab practical, ADC input comes from the output of the sensor circuit with Op-Amp as well. So we have to control the output of the sensor circuit (after heat up the sensor) to be less than 5volts.

So here it is.