sht10 with pic 16f917 wrong measurement

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pajithrao

Joined: 29 Oct 2009
Posts: 3

31 Oct 2009 16:40 sht10 with pic 16f917 wrong measurement

i am attaching a vb screen shot which shows the temperature and humidity taken as 14 bit and 12 bit respectively. It also shows the communication between the microcontroller and sht10. The info is passed to pc thru serial communication. Each line is one full set of communication.
R stands for com reset.
s stands for transmission start
s-f is softreset command
s-u is status write command
u-w is data written into status reg
s-v is status read command
v-x is status reg data read - which is different from what i wrote into it problem no. 1
x-z is checksum
s-t is temperature measurement command
t-j is msb of temp
j-k is lsb of temp
k-r is checksum
s-h is humidity command
h-y is msb of humidity
y-next eight bits is lsb of humidity
temperature count is shown top box next to humidity text box
humidity count is shown in top right box
the air temperature and humidity was 26.5 and 55%

the sht10 was manually soldered and no recharge time was given. will the humidity and temperature come back to the actual value after a day or is there some problem in the communication

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wp100

Joined: 15 May 2009
Posts: 327
Helped: 45
Location: England

31 Oct 2009 17:34 Re: sht10 with pic 16f917 wrong measurement

Hi,

Cannot help with all your VB code but as the datasheet says you should allow time for the sensor to recover after soldering - although I did not notice any great problem.

Unless you have a known good humidity sensor to work against perhaps you should do a salt box calibration on the SHT10 - see this pdf for details for how to do this -
with common house salt you should get 75% at 20 -25 deg C - ensure you do just moisten the salt and not turn it into a runny mess.

http://www.cma.science.uva.nl/english/Resources/Manuals/d0381.pdf

FvM

Joined: 22 Jan 2008
Posts: 5161
Helped: 767
Location: Bochum, Germany

31 Oct 2009 18:53 sht10 with pic 16f917 wrong measurement

I think, before getting a meaningful temperature measurement, you don't need to think about calibrating the humidity sensor...

Either the communication setup or the calculation is obviously wrong. Your screenshot isn't really helpful to decide between both options.

pajithrao

Joined: 29 Oct 2009
Posts: 3

01 Nov 2009 16:53 Re: sht10 with pic 16f917 wrong measurement

Does the temperature reading also get affected by soldering?
any source code for communication with sensor?
what is the slowest clock that can be applied to sck?

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wp100

Joined: 15 May 2009
Posts: 327
Helped: 45
Location: England

01 Nov 2009 19:02 Re: sht10 with pic 16f917 wrong measurement

Hi,

Quote:

Does the temperature reading also get affected by soldering?

Doubt it, I believe it is a separate sensor.

Quote:

any source code for communication with sensor?

There is example code on the Sensirion site.

Quote:

what is the slowest clock that can be applied to sck?

See the data sheet for full details

pajithrao

Joined: 29 Oct 2009
Posts: 3

04 Nov 2009 17:06 Re: sht10 with pic 16f917 wrong measurement

I got the problem solved. i just needed to pulse before i read the data pin. i was reading after clocking it. so the data moved a bit left increasing the count. I made a temp oscilloscope monitoring from the laptop. and i found what was the mistake.
thanks all of u who replied