I'm trying to calibrate my thermistor and first way i'm trying is using a ds18b20 as source to calibrate the thermistor.
when reading the temperature from both sensors i noticed the thermistor is about 2.2 degrees off, so i added that 2.2 in thermistor temperature calculation, now the reading from both sensors are almost the same.
for example the reading right now is:
Thermistor: 26.42 C
DS18B20: 26.37 C
from 25 degrees to 35 degrees both sensors readings are similar (thermistor response is way faster to temperature change) but i didn't tested it below 25 degrees.
my question is how accurate this method of calibrating can be in huge temperature changes like -10 or +80? is it still gonna be as accurate as it is in 25-35 range of temperature?
my question is how accurate this method of calibrating can be in huge temperature changes like -10 or +80? is it still gonna be as accurate as it is in 25-35 range of temperature?
That depends on the thermistor used. As you didn't specify which type you're using and how you calculate the result it's hard the predict any result.
J35U51510V3:
I'm trying to calibrate my thermistor and first way i'm trying is using a ds18b20 as source to calibrate the thermistor.
There are several sources of experimental error with temperature measurements. Firstly sensors pick
up conducted heat and radiated heat, and in a ratio that depends on the sensor shape, construction and
surface materials.
Also the time constant for a sensor to equalize with its surroundings can be tens of seconds or even more.
You are best placing both sensors inside a small closed metal tube (to reflect radiant heat and spread
conducted heat), and use a rapidly stirred water-bath. The temperature of the water should be raised
in steps, then the sensors allowed to equalize in temperature for a minute or so before taking each
measurement.
If you just have sensors on the bench I would expect upto 2 degrees error just because you are at the
bench radiating heat at them.
when reading the temperature from both sensors i noticed the thermistor is about 2.2 degrees off, so i added that 2.2 in thermistor temperature calculation, now the reading from both sensors are almost the same.
for example the reading right now is:
Thermistor: 26.42 C
DS18B20: 26.37 C
from 25 degrees to 35 degrees both sensors readings are similar (thermistor response is way faster to temperature change) but i didn't tested it below 25 degrees.
my question is how accurate this method of calibrating can be in huge temperature changes like -10 or +80? is it still gonna be as accurate as it is in 25-35 range of temperature?
A thermistor does not follow the change in
temperature in a linear manner. So, the wider
the difference in temperature from the calibration
point, the more error may be seen.
Herb