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manish12
Joined: 21 Nov 2006
Posts: 1020
Helped: 31
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 19 Dec 2007 10:21 hummidity look up table? |
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a resistive(two pin small in size like switch pad on pcd ) humidity sensor i am using.
i need lookup table for this sensor
thanx
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ravimarcus
Joined: 09 May 2005
Posts: 204
Helped: 19
Location: Bangalore, INDIA
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20 Dec 2007 15:17 Re: hummidity look up table? |
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| manish12 wrote: |
| a resistive(two pin small in size like switch pad on pcd ) humidity sensor i am using. i need lookup table for this sensor |
If it is resistive, then you will be measuring the voltage and this voltage will be linear. Without the data sheet it will difficult to provide a LUT.
Cheers
Ravi
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manish12
Joined: 21 Nov 2006
Posts: 1020
Helped: 31
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20 Dec 2007 16:26 Re: hummidity look up table? |
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still , i want LUT.
VCC---\/\/\/\/\------0/P-------/\/\/\/\/\----------GND
r=10k r(h)
at what volt ? , what i will show on display ?
it is my q ? simple .....................
i can connect any(suggested) value in place of r=10k ,if required
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ravimarcus
Joined: 09 May 2005
Posts: 204
Helped: 19
Location: Bangalore, INDIA
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20 Dec 2007 17:27 Re: hummidity look up table? |
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| manish12 wrote: |
still , i want LUT.
VCC---\/\/\/\/\------0/P-------/\/\/\/\/\----------GND
r=10k r(h)
at what volt ? , what i will show on display ?
it is my q ? simple .....................
i can connect any(suggested) value in place of r=10k ,if required |
For this you will need to know what is the resistance change per unit change of humidity.
Cheers
Ravi
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manish12
Joined: 21 Nov 2006
Posts: 1020
Helped: 31
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20 Dec 2007 17:37 Re: hummidity look up table? |
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so , where i am wrong ?
indirectly, same think ?
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kender
Joined: 19 Jun 2005
Posts: 1231
Helped: 88
Location: Stanford, SF Bay Peninsula, California, Earth, Solar System, Milky Way
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20 Dec 2007 21:01 hummidity look up table? |
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Make a LUT via calibration.
1. Take a precision humidity sensor as a standard.
2. Gradually increase the humudity over your interval of interest.
3. Measure voltage from your voltage divider
4. Make a LUT: measured voltage vs. reading of the precision humidity sensor.
P.S. Could you post a model or a datasheet for your sensor? May be there's an easier way.
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manish12
Joined: 21 Nov 2006
Posts: 1020
Helped: 31
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21 Dec 2007 5:29 Re: hummidity look up table? |
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thank you,
| Quote: |
| 2. Gradually increase the humudity over your interval of interest. |
but ,how ????
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kender
Joined: 19 Jun 2005
Posts: 1231
Helped: 88
Location: Stanford, SF Bay Peninsula, California, Earth, Solar System, Milky Way
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21 Dec 2007 5:46 Re: hummidity look up table? |
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| manish12 wrote: |
| Quote: |
| 2. Gradually increase the humudity over your interval of interest. |
but ,how ???? |
It depends on the equipment you have. There are special environmental chambers that can vary temperature and humidity. But, I guess, since you're asking, you don't have access to one of those.
You can take a sealed jar, add portions of water to it and increase the temprature. That way you'll increase the absolute humidity (kg_water/m^3).
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fala
Joined: 18 Sep 2005
Posts: 250
Helped: 15
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21 Dec 2007 5:51 hummidity look up table? |
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| Manish You need to use a calibrated humidity sensor so you can build your LUT according to calibration with that.
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manish12
Joined: 21 Nov 2006
Posts: 1020
Helped: 31
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21 Dec 2007 6:56 Re: hummidity look up table? |
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| Quote: |
Manish You need to use a calibrated humidity sensor so you can build your LUT according to calibration with that.
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I GET IT , NEED CALIBRATION ,NEED STD METER.
what happen ,i am in small town , where this humidity has to display , but for present i am not find any std humidity meter to calibration . where i am present now!.
what , i did , i call to my brother and ask present humidity at my city(home) , adj the series resistants accordingly, and check it 5-6 times( interval 4h) with my non-std to std, and readj(r and prog).
tell me , is this ok !.
after this i guess , no meter is std meter..............sorry to say.
than you .
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ravimarcus
Joined: 09 May 2005
Posts: 204
Helped: 19
Location: Bangalore, INDIA
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21 Dec 2007 7:19 Re: hummidity look up table? |
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Your method is partially ok, but not perfect.
First of all, where did you get this sensor?, Do you have a data sheet for this? Do you have a part no. for this sensor? If you can give any of this, then we can help you out.
Cheers
Ravi
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manish12
Joined: 21 Nov 2006
Posts: 1020
Helped: 31
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21 Dec 2007 7:32 Re: hummidity look up table? |
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no part no: i have .
see my first post , no data sheet , no graph : humidity vs r(h)
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ravimarcus
Joined: 09 May 2005
Posts: 204
Helped: 19
Location: Bangalore, INDIA
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21 Dec 2007 7:37 Re: hummidity look up table? |
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| manish12 wrote: |
| no part no: i have. see my first post , no data sheet , no graph : humidity vs r(h) |
Hmmm. Measure the resistance and get to know the humidity at your place. When the humidity changes, repeat the procedure above. You will get a difference in resistance to a difference in humidity. With this you will be able to build a table.
Cheers
Ravi
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21 Dec 2007 7:37 Ads |
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manish12
Joined: 21 Nov 2006
Posts: 1020
Helped: 31
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21 Dec 2007 7:40 Re: hummidity look up table? |
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you thinking right but humidity vs resi . .....is not linear one
like temp sensor 10mv/'c
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ravimarcus
Joined: 09 May 2005
Posts: 204
Helped: 19
Location: Bangalore, INDIA
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21 Dec 2007 7:43 Re: hummidity look up table? |
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| manish12 wrote: |
you thinking right but humidity vs resi . .....is not linear one
like temp sensor 10mv/'c |
Then you are really in problem  .
BTW, where did you buy this sensor from?
Cheers
Ravi
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manish12
Joined: 21 Nov 2006
Posts: 1020
Helped: 31
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21 Dec 2007 13:10 Re: hummidity look up table? |
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| FROM LAMING TON ROAD MUMBAI , INDIA
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ravimarcus
Joined: 09 May 2005
Posts: 204
Helped: 19
Location: Bangalore, INDIA
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21 Dec 2007 14:04 Re: hummidity look up table? |
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Oh, then you can never get the data sheet. They are there only to sell and make money. Do one thing. Search the net for a resistive type humidity sensor. Use that data sheet and try to linearize. You may succeed.
Cheers
Ravi
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watermelon
Joined: 08 May 2007
Posts: 77
Helped: 8
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21 Dec 2007 15:36 Re: hummidity look up table? |
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Go to a college physics lab and look at the [b]wet & dry bulb humidity meter [/b]working principles.
Use this to calibrate your sensor.
Also, check the effect of temperature on your sensor.
Also, you could convert the LUT into an equation using [url]http://math.fullerton.edu/mathews/n2003/NumericalUndergradMod.html[/url]
And then correct the values in a microcontroller or analog circuit.
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manish12
Joined: 21 Nov 2006
Posts: 1020
Helped: 31
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21 Dec 2007 15:39 Re: hummidity look up table? |
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thank you ,
i get the old lut , from college library, it is just alternative , not exact but ,still ok.
thank you all .
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