HTS221 Incorrect Temperatures / Calibration (T0_OUT = 0)

[Simon Sq]

Hi,

I'm having an problem whereby I believe the temperature readings from an HTS221 device are incorrect. They seems to be around 5degC too high compared to reference temp. I'm using a Nest thermostat as the reference, and while this may not be calibrated I would still expect the temperatures to be roughly similar.

I have suspicion that the calibration registers aren't correct, specifically the T0_OUT value which is zero. Is a value of 0 for T0_OUT expected or is there something wrong with the calibration? Seems a bit suspect to me.

Below is a dump of all the calibration registers:

Calibration Registers

Addr: 0x30  Value: 0x3d
Addr: 0x31  Value: 0x8f
Addr: 0x32  Value: 0x99
Addr: 0x33  Value: 0x0e
Addr: 0x34  Value: 0x00
Addr: 0x35  Value: 0xc4
Addr: 0x36  Value: 0xf2
Addr: 0x37  Value: 0xff
Addr: 0x38  Value: 0x3a
Addr: 0x39  Value: 0x03
Addr: 0x3a  Value: 0xf5
Addr: 0x3b  Value: 0xd0
Addr: 0x3c  Value: 0x00
Addr: 0x3d  Value: 0x00
Addr: 0x3e  Value: 0x1e
Addr: 0x3f  Value: 0x03

So for the linear interpolation of temperature I get the following:

x0 = 0
y0 = 19.125 degC
x1 = 798
y1 = 33.75 degC

However using those values yields temperatures which are too high (by approx 5degC). The humidity also appears to be around 10% lower than the Nest thermostat.

Hardware and Software

I'm using the HTS221 driver from the ST Micro MEMS library. The HTS221 is mounted on a MikroE Click board (https://www.mikroe.com/temp-hum-click) attached to an Azure Sphere dev kit.

At the moment I don't have another HTS221 device to compare with.

Device Configuration:

Data Output Rate: 7Hz

Averaging: H: 512, T:256

Heater: Off

Block Data Update: Enabled

Samples are being read from the device at approx. 1Hz.

Any advice would be appreciated.

Thanks,

Simon

[Eleon BORLINI]

Hi Florin,

I understand the point, but unfortunately we don't usually send golden samples except to key customers.

For this reason, I suggested you to contact regional Sales offices and Representatives from this link.

By the way, in general ST MEMS sensors are not indeed 1k$-to10k$ devices equipped with their own dedicated datasheet...

-Eleon

[AShuk.4]

hi,

Is there any solution for this issue.

I am using a MKR IoT Carrier with HTS221 sensor. The device is sending a approximately a 5 degree higher readings everytime. I believe this thread is discussing same issue.

Kindly share a fix.

BR,

Ajna

[Eleon BORLINI]

Hi Ajna @AShuk.4​ , all,

please note that you are using a "third-part" board, and ST cannot guarantee that the performances declared on the datasheet are then met after an unknown soldering process.

Even for STEVAL-MKI141V2 adapter you might be careful.

For this reason, I suggest you to characterize the offset and maybe the gain shift of the parts from the datasheet and "calibrate" them at software leverl, if you need a very accurate application setup.

I also suggest you to collect all your experiences and try asking the question on MKROE forum at this link.

-Eleon