Why are my HTS221s getting bad Humidity values?

[M.Mardini]

Hello,

My company is using since more than one year a combination from HTS221 and stm32f407 uController , I2C is used.

The problem is that on some devices i have from the sensor different results.

also some sensors give correct output where the others give lower values, where both of them have the same circumstanses. like the same board design and the same uController firmware.

in the attachment there are the output data from two sensors.

I wonder where the problem could be?

We use the follwing adjustment :

PD = 1: active mode

1Hz

other CTRL-REG are disabled,

we have activatet the heat register for 4 seconds,but that did not solve the problem.

we are very thankful for any help :grinning_face:

[M.Mardini]

Update, the assmbler company told me that they did not do any re-hydration. what can i do in this situation ?

we are very thankful for any help :grinning_face:

[Eleon BORLINI]

Hi @M.Mardini​ ,

if also the heater doesn't sort any effect (this would have been the first thing I would have suggested you) you could try with a bake procedure at 85° (and 85RH), that should help to remove residual condensation on Sensor1, that seems to have prevented the measurement of the correct humidity.

The temperature you are measuring is ok?

Hope it is not damaged from a contaminating assembly...

-Eleon

[M.Mardini]

Hi @Eleon BORLINI​ , thank you very much for your Answer

we have baked the sensor with 70RH at (35°) for 12 hours (Data sheet). and today with 85RH for 1 hour, but that did not have any effect.

The Temperature measurement is Ok.

[Eleon BORLINI]

Hi @M.Mardini​ ,

which is the failure rate on your sensors? I mean, the number of devices not behaving well

And do the wrong data affect devices since the beginning, or do they fail after some time?

I'm by the way afraid it could be an issue related to the soldering process...

-Eleon