I have a radio controlled weather station which has always shown 2°C less than the environment in which it is placed for the remote sensor, verified by good quality mercury thermometer and a couple of other systems I also have.
I particularly like this station as it shows sun rise/set and moon rise/set for my city and the overall data presentation is quite good. So I decided to try and improve the accuracy.
The remote module uses an NTC for temperature so my first step was to remove this and do a calibration curve. I recorded 10 points from 5°C to 35°C and did an X/Y plot with Excel. Data shows linear relationship with R² of 0.98 which is a pretty go fit. The NTC value for 25°C is 44K which is little odd but could be a custom sensor.
Looking to my data set a 2°C increase would need a reduction in resistance of 3K (I wonder if the software is expecting a 47K NTC as mine 44+3 would be 47K coincidence ?).
I think the measurement is using a voltage divider.
Calculating a resistance in parallel I need to get the 3K reduction I get 1 Meg ohm, or so I think.
I would be most thankful if some one with more knowledge could cast an eye I over what I have done and point out any mistakes or erroneous assumptions I have made before I start soldering.
I haven't posted the data but if any one is interested I will.
TC
I particularly like this station as it shows sun rise/set and moon rise/set for my city and the overall data presentation is quite good. So I decided to try and improve the accuracy.
The remote module uses an NTC for temperature so my first step was to remove this and do a calibration curve. I recorded 10 points from 5°C to 35°C and did an X/Y plot with Excel. Data shows linear relationship with R² of 0.98 which is a pretty go fit. The NTC value for 25°C is 44K which is little odd but could be a custom sensor.
Looking to my data set a 2°C increase would need a reduction in resistance of 3K (I wonder if the software is expecting a 47K NTC as mine 44+3 would be 47K coincidence ?).
I think the measurement is using a voltage divider.
Calculating a resistance in parallel I need to get the 3K reduction I get 1 Meg ohm, or so I think.
I would be most thankful if some one with more knowledge could cast an eye I over what I have done and point out any mistakes or erroneous assumptions I have made before I start soldering.
I haven't posted the data but if any one is interested I will.
TC