Hi, I pretty much know nothing about thermistors and how to select them.
I need a thermistor that linearly increases resistance from 100k to 200k, when temperature linearly rises by 75C. Can you help me out?
You will not find a thermistor that can do that. Thermistors are by nature non-linear, and can't be selected by resistance range like that. It would have to be an IC or otherwise active circuit that convereted a thermistors output linearly into an equivilant transistorized ouput resistance in the desired range.
If your looking for an analogue device, perhaps the **broken link removed**will work for you?
It provides a 10mV/Degree output, and the scale depends on how it wired up.
Here's an example for a -55 to +150 degree temperature sensor (there are simpler ways to go about it, check the LM35DZ datasheet) **broken link removed**
A great digital solution is the **broken link removed** **broken link removed**
I'm working on a pH probe amplifier and the mV output of a pH probe is dependant on temperature (and the concentration of H+ ions ofcourse). So I need some sort of temperature compensating device or circuit that'll decrease the gain of the probe's non-inverting amplifier as temperature increases and vise versa.
Some kind of LM35DZ circuit would be perfect; i better get cracking. Thanks gramo and everyone!
G'Day Gramo,
Ref the Lm35, I did find when I did tests using +5V to the device, with two diodes to 0V, I had linearity problems near the high tempr end.
The spec sheet says Vop = 4 to 30V, with a +5Vs and Vdp of 1.4V with two diodes, the Vs across the LM35 is only +3.6V.
I had to increase the Vs, as I had a +9Vs on the board, used that and it cleared the problem. EDIT: Look at the Datasheet Fig #7, the +5V is now +Vs!
Liked your movie, yesterday, re the stepper, nice one!, answered the OP's query.
Will buy you a film Directors chair at Xmas.