Hi,
I'm a Physics degree student with no real experience of digital electronics. Part of my project involves making a temperature measuring system which can operate over a range of -10 to 100 degrees celcius. So far I have managed to preform an analogue to digital conversion (via a PIC) on an LM35C thermistor. I then output the digital value via RS232 to a PC.
The problem is the range of values I get out. The voltage on the signal pin of the LM35C ranges between approximately 0.24V at room temp to 0.51 degrees at approximately 60 degrees C. This seems ok however this only corresponds to a small change in the PICs digital output.
At the moment I have set the PIC output to be a 3 digit number between 256. This means that I should get 256 divisions in the thermistors range. However, the above temperature change only gives a digital change of 15!!!
Does anyone know how I can fix this without Op-amps?
Will lowering the the Vref on the PIC fix this problem?
Are there any probelms in doing this?
All help gratefully received.
Tom
I'm a Physics degree student with no real experience of digital electronics. Part of my project involves making a temperature measuring system which can operate over a range of -10 to 100 degrees celcius. So far I have managed to preform an analogue to digital conversion (via a PIC) on an LM35C thermistor. I then output the digital value via RS232 to a PC.
The problem is the range of values I get out. The voltage on the signal pin of the LM35C ranges between approximately 0.24V at room temp to 0.51 degrees at approximately 60 degrees C. This seems ok however this only corresponds to a small change in the PICs digital output.
At the moment I have set the PIC output to be a 3 digit number between 256. This means that I should get 256 divisions in the thermistors range. However, the above temperature change only gives a digital change of 15!!!
Does anyone know how I can fix this without Op-amps?
Will lowering the the Vref on the PIC fix this problem?
Are there any probelms in doing this?
All help gratefully received.
Tom