I'm trying to find the optimal, or at least a good resistor to put into a voltage divider to measure a thermistor, and an electro-conductivity K10 probe. The range is 10 uS/cm to 1 S/cm, and an operating temperature of 0-70 Celsius.
So equations gave me a working resistance of ~80 ohms to 19M ohms. I'm thinking that given the range of resistance it might be difficult to have a single resistor to compensate.
Also I'm using a 1k thermistor, and was wondering if in that case a 1k would be the optimal resistor to pair with that as well?
____/\/\/\_____thermistor____ |||gnd
| ? | probe
(5v dc) mcu
I've played around; seems a 10k is more accurate in getting the value of the thermistor.
So if I have known solutions, and a known probe the resistance should be in theory known. A K 10 probe and a .15 S solution should come out w/ 1.5 ohm?, or would it be ohm/cm?
Best Answer
A silicon diode is a fine voltage = log(current) converter, with 58 milliVolts per decade of current (at room temperature).
Just connect the thermistor to a reasonably steady power supply, and connect other end to anode[arrow] of silicon diode, then ground the cathode[bar].
simulate this circuit – Schematic created using CircuitLab