# Temperature sensor help.

Discussion in 'Homework Help' started by thisonedude, Apr 26, 2014.

1. ### thisonedude Thread Starter Member

Apr 20, 2014
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0
I'm working with Diodes and we have to find the the voltage difference between two diodes, (one being a reference at constant 25 C and the other changes temperature). I'm just having trouble with the last of of the assignment. It asks to determine the sensitivity of the temperature sensor in milivolts per C. What temperature would i use and how would i calculate it?

2. ### paulktreg Distinguished Member

Jun 2, 2008
625
125
You know the voltage across the diode at two different temperatures?

By how much does the voltage change per deg C?

Have a look at some data sheets, the 1N4148 for example.

3. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,518
515
Well. If this is experiment, then you should have some data. You put your data into the spreadsheet, then you plot it. You put temperature on the x axis. You put voltage on the y axis. Now you have relationship of temperature to voltage in the form of: Voltage=slope*Temperature. Find slope.

Or you can do it the way paulktreg alluding to. The plot I described above should be a line. From geometry, what is the very basic requirement for a line? The very basic requirement is to have two points. What is also a very basic requirement for finding a slope of the any line? The very basic requirement to find a slope of any line is to have two points that are anywhere on the line.
So.
You have two points, find the slope. If you keep the units of measurement you will see that slope is in Volts/°C. So just change volts to millivolts.

4. ### davejo New Member

Aug 1, 2012
6
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@thisonedude: Hi, it is very easy to find the sensitivity of the diode like the one temperature you should use the room temperature 25C and for the other temperature you can use whatever you want and now you have two values of temperature and voltage. So the sensitivity is:
Sensitivity=V2-V1/T2-T1