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Using 1N4148 As A Temperature Sensor

Posted: Fri Jul 28, 2017 10:23 am
by miyayoung520
Can I know which component senses heat or acts as heat sensor in the following circuit? In the given diagram, it is said that the 1N4148 diode acts as the sensor. But basically it is a zener diode and I don't think that it is able to sense temperature shift. This circuit provides a working model but the sensor remains as a mystery for me. Can you please help it for me? Here is the datesheet of 1n4148 .

Re: Using 1N4148 As A Temperature Sensor

Posted: Mon Sep 04, 2017 1:36 pm
by grendell
Hi there,
I could not see your circuit however, any semiconductor forward voltage will change with temperature. If you look at fig 1 of your datasheet for the 1N4148 you will see that at (for example) 1mA the forward voltage is about 0.7v @ 25c but drops to 0.4v @ 125c. This is quite a small change for 100c and the actual voltages are rather small for use with an A-D (however you could put a few in series!
The main advantage is the 1N4148 is cheap, rugged and is good for use at a highish temperature.