Accuracy of SHTxx
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Posts: 46,084
Hi All,
I compared two SHT11 sensors side by side. They were in close agreement,
within +/- a few tenths of a degree C. However, both of them read almost two
degrees high against a lab grade thermometer of know accuracy (it's within a
couple of tenths). Anyone else checked the accuarcy of these sensors, and if
so what did you get?
Jonathan
I compared two SHT11 sensors side by side. They were in close agreement,
within +/- a few tenths of a degree C. However, both of them read almost two
degrees high against a lab grade thermometer of know accuracy (it's within a
couple of tenths). Anyone else checked the accuarcy of these sensors, and if
so what did you get?
Jonathan
Comments
>
>I compared two SHT11 sensors side by side. They were in close agreement,
>within +/- a few tenths of a degree C. However, both of them read almost two
>degrees high against a lab grade thermometer of know accuracy (it's within a
>couple of tenths). Anyone else checked the accuarcy of these sensors, and if
>so what did you get?
>
>Jonathan
Hi Jonathan,
In spot checks, I've found the SHT15 to be within the +/- 1 degree F
specification. I'm comparing with an LM34 that was calibrated against
a NIST traceable lab thermometer.
It is hard to get a good comparison. Be sure to follow the warning
to make less than 3 readings per second (at 5 volts power) to avoid
self-heating. Of course, be sure that the internal heater is OFF!
And be sure the SHTxx is mounted well away from other sources of heat
on circuit boards.
That said, it is sometimes hard to compare temperatures of two
thermometers that have different constructions, i.e., the SHTxx vs an
immersion-type mercury-in-glass thermometer. The radiation
properties and the time constants are very different, so they have to
be wrapped up or enclosed in a thermos with plenty of time for
equilibration.
I'm interested to hear what further results you find with it.
-- best regards
Tracy Allen
electronically monitored ecosystems
http://www.emesystems.com
mailto:tracy@e...
Well, I tried a cheesy thermos set up, dangling the SHT11 and the
thermometer into a thermos. As the thermometer was too long to actually
hang, I put it on a foam pad to insulate it from the bottom. I went back and
changed the code to make sure it was way less than 3 calls per second for
both temp and humidty. After over an hour, still exactly the same accuracy,
the SHT11 appears almost 2degs off.
I will put together a LM34 sensor and stuff it in there and see what I get.
I am also allowing the thermos test to continue.
If I get the chance, I will do a wet bulb type test on the humidty reading
and see what I get. Unfortunately I don't have two good lab grade
thermometers, so I will have to use the same one and perform the test as
quickly as I can. May not be perfect, but should be close.
Jonathan
Original Message
From: "Tracy Allen" <tracy@e...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, January 07, 2003 11:15 AM
Subject: Re: [noparse][[/noparse]basicstamps] Accuracy of SHTxx
> >Hi All,
> >
> >I compared two SHT11 sensors side by side. They were in close agreement,
> >within +/- a few tenths of a degree C. However, both of them read almost
two
> >degrees high against a lab grade thermometer of know accuracy (it's
within a
> >couple of tenths). Anyone else checked the accuarcy of these sensors, and
if
> >so what did you get?
> >
> >Jonathan
>
>
> Hi Jonathan,
>
> In spot checks, I've found the SHT15 to be within the +/- 1 degree F
> specification. I'm comparing with an LM34 that was calibrated against
> a NIST traceable lab thermometer.
>
> It is hard to get a good comparison. Be sure to follow the warning
> to make less than 3 readings per second (at 5 volts power) to avoid
> self-heating. Of course, be sure that the internal heater is OFF!
> And be sure the SHTxx is mounted well away from other sources of heat
> on circuit boards.
>
> That said, it is sometimes hard to compare temperatures of two
> thermometers that have different constructions, i.e., the SHTxx vs an
> immersion-type mercury-in-glass thermometer. The radiation
> properties and the time constants are very different, so they have to
> be wrapped up or enclosed in a thermos with plenty of time for
> equilibration.
>
> I'm interested to hear what further results you find with it.
>
>
> -- best regards
> Tracy Allen
> electronically monitored ecosystems
> http://www.emesystems.com
> mailto:tracy@e...
>
>
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