Hello,
I need to calculate temperature based on 100k thermistor (built in device I have). I got ADS1110 from M5Stack and some esp for that. I wired everything and have some readings, but I’m not sure how to correctly wire ADS with thermistor to read resistance. I saw there is single ended mode, differential mode, should I supply thermistor with external voltage etc.
Thank you for any help!
Yes, you will need to use the thermistor with a fixed resistor to make a voltage divider. Give the voltage divider a known input voltage like 3.3V and use the ADS to measure the output voltage. Single ended mode is all you need, but be sure to use a 1% tolerance resistor and a precise input voltage, if you need a precise temp reading.
Thermistors don't have a perfectly linear relationship between resistance and temperature, so if you want high precision you may need to use something a little more sophisticated than a linear equation to convert voltage to temp.
With a "normal" voltage divider, single-ended mode (referenced to ground) should be fine.
As a quick-check, two fixed 100K resistors as a voltage divider will give you half of the supplied voltage. Presumably, the voltage applied to the voltage divider is the same as as the ADC reference.
Typically thermistors are specified/calibrated for 25 degrees C (you can check your specs) so two 100K fixed resistors should equate to a reading of 25 degrees.
You should also check with the ADC directly connected to the maximum voltage and to ground just to confirm it "makes sense"
Although the thermistor is fairly linear (resistance vs. temperature), a voltage divider is NOT linear. i.e A 50% change in resistance doesn't make a 50% change in voltage.
You can find formulas/algorithms for measuring temperature with a thermistor that will take care of that.
...I doubt that you need a separate DAC.
Thank you a lot @PaulRB! Can I summarize:
Thanks for the tips 
! It is for coffee machine and +/- 1 degree will be fine. I know I need to use Steinhart-Hart formula to calculate dependency between resistance and temperature. I carefully measure resistance and temperature on my machine and I’m ready to experiment!
What is the potential error values for those readings?
Do you know the coefficients to use for your particular thermistor?
esp itself has 1.1V ADC and I found out some online thermistor calculator which allows you to input some values and with 3.3Vref, 100k thermistor and playing with different values of fixed resistor I was not able to find out proper value to get whole needed range like 10-110 degree C 
More details please. Links to that calculator, the values you tried etc.
The max voltage of the ADC should not matter.
The ADS and the ESP have the wrong type of A/D for a thermistor. The ADS could give you unstable readings, because you need to have a supply for the thermistor's voltage divider that is stable within about 0.1mV to match the 15-bit single-ended resolution of the ADS. An impossible task.
If your temp range is 10C to 110C, then why not use a digital sensor, like the DS18B20.
Leo..
I have something like this:
9k - 94°C
12k - 85°C
13k - 82°C
14k - 79°C
15k - 77°C
yes, it is NTC
https://www.electro-tech-online.com/tools/thermistor-resistance-calculator.php
I play a little bit and probably with 2k Ohm pull-down it could work 
yes, I love this idea, but I'm building around existing solution and 100k NTC thermistor is built in machine
Then there is no problem and no need for calibration.
No. The value of the fixed resistor must be the same as the thermistor at the temp of interest for max temp resolution. A 100k thermistor is about 10k at 80 degrees C, so 10k seems a good value.
I don't see how an ADS1010 could improve the result over the A/D of an ESP.
Leo..
@PaulRB could you help me with wiring, because I have doubts how it should be (post #4)
Thank for this message - I didn't know this rule. Could you share some sources to read about it more?
With 10k resistor and 3.3Vref you will get 1.33V or 1.97V (depends on if resistor is pull down or up) - it will be out of the 1.1V range of ADC in ESP.
You described the wiring of the thermistor on the right of the diagram you linked to (assuming that by "fixed thermistor" you meant to say "fixed resistor").
But generally the wiring of the thermistor in the middle of the diagram is preferred because it's safer (+V does not need to be wired off the main circuit board to the thermistor).
