SHT_75 with picbasic pro
Hi Dave,
Thanks a lot for your reply on the matter.
I will try to better clarify the problem that I have using the SHT15.bs2 ver.C program from Tracy Allen ( emesystems).
Point _1.
The program reads the raw temperature and store it on the " result " word variable.
The temperature is obtained using the following : degC=result+5/10-400.
This means that if the result is 5000 we have +10°C, if the result is 4000 temp is 0°C
and if 3000 the temp is -10°C. I modified the program in order to "display" the minus sign
when result is less then 4000. Result is the 14 bit raw temperature delivered by the sensor.
Up to here everythings is correct and my system shows the correct temperature. I did some comparison with the airport control tower close to my home : it is consistent.
Point _2
the program then reads the raw RH (12 bit ) and stores that value on the "result" word variable.
RH is then obtained as follows: RH=(26542-(54772**RESULT+RESULT))**RESULT-40.
At this point everything is ok to me : my PIC micro gives me the correct RH value.
Point_3
The program computes now the temperature compensated RH in two steps:
First step > RHtc=655+(RESULT*5)+(RESULT**15917)
Second Step > RHtc=(RHtc**(degC+2480))-(RHtc**2730)+RH
>>> At this point the RHtc is correct only if the temperature is above 0°C or, if the raw temperature data from the sensor is more than 4000 !.
If the temperature is negative e.g. -1.7 °C the RHtc is not correct. It is about 172%.
The control tower gives me T=-1.7°C , rh=85% and Dew point of -3.9°C.
>>> This is my problem.
I will appreciate very much if someone can give me an help to solve the troble.
May be that some other programmer ( I am not a programmer ! ) have already solved it !
Thanks in advance
Regards,
73!
Ambrogio
IW2FVO
P.s.: English is not my first language and I am not sure to have express my problem correctly: I am Italian !
Originally Posted by Dave
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