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Topic: Hooking up a 10K NTC Thermistor to an LTC2440 (Read 1 time) previous topic - next topic

dhenry

Quote
I read in the datasheet that IN+ is +VREF/2 and IN- is -VREY/2
Would this mean I only use half of the measurement range which would be -2,5V to +2,5V and I am using 0V to +2,5V?


Since you are not measuring differentially, have two options:

1) increase the 10k resistor's value. Make it a 20k for example.
2) flip the divider: so that as temperature rises the divider's output goes down from Vref/2. This approach works if you expect temperature to go up from room temperature.

Pebbles


Quote
I read in the datasheet that IN+ is +VREF/2 and IN- is -VREY/2
Would this mean I only use half of the measurement range which would be -2,5V to +2,5V and I am using 0V to +2,5V?


Since you are not measuring differentially, have two options:

1) increase the 10k resistor's value. Make it a 20k for example.
2) flip the divider: so that as temperature rises the divider's output goes down from Vref/2. This approach works if you expect temperature to go up from room temperature.


Alright I'll try and increase the 10k resistor value and see if that works.
I'll let you know if it has worked.

Pebbles

I've tried a 20k resistor and it did not work.
I then used a 150 ohm resistor, this worked. I am getting higher values now.

I will continue experimenting a bit with this.

dhenry

For it to work for your chip, you need a ntc on bottom of the divider; or a ptc on the top of the divider -> so when temperature rises, the output voltage goes down.

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