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 Author Topic: Temperature measurement with NTC thermistor  (Read 579 times) 0 Members and 1 Guest are viewing this topic.
Catcatcat
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 « on: May 29, 2023, 07:45:18 07:45 »

Hi all!

I decided to share another tool that I developed for myself and use it to design temperature measurement systems using NTC resistors.

NTC resistors are a very cheap component, their feature is that due to their small size they can perform very fast temperature conversions.

At the beginning, I avoided using them because of the complexity of calculating the formulas that are always given in the datasheet for the components. But when I had to take off all the same, I discovered for myself a mechanism that allows even on the slowest MCUs to perform temperature readings almost instantly. Moreover, the conversion accuracy over the entire temperature range is an order of magnitude superior to factory calibrated digital and analog sensors. For this method, there is no need for a stable reference voltage for the ADC and the measurements are independent of the MCU power supply.

The method is that we need to get a table of ADC values for the existing sensor, in the required measurement temperature range.

The whole problem is where to get the RT characteristic for the sensor. Some manufacturers and dealers provide such information for the selected sensor. Can be obtained in increments of one degree, which is sufficient for high-precision temperature measurement. But some are given in increments of 5, or even 10 degrees. Others provide no information at all.

Quite often you have to deal with such a task that there is a sensor, but there is no description for it at all or it is very short.

For which option I suggest the following tools:

NTC constant calculater by Catcatcat.xlsx - a tool for professionals that allows you to restore the sensor resistance table using four control points, convert it to the required step and get the ADC value depending on the circuit used.

Calculation of the ADC table by Catcatcat.xlsx is a simplified tool designed only to convert NTC resistor data into ADC codes. I recommend it if you have a factory temperature sensor resistance table with a step that suits you completely.

NTC_sensor library for temperature measurement.

If you are interested in more details, you can read here, use Google translator. Attached are the main tools, the library can be downloaded from my website.

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