HTS221 and condensation

[GShim]

The HTS221 has an internal heater to "speed up the sensor recovery time in case of condensation".

1. How do I identify a condensation state?
2. How long the heater has to be activated, in order to recover from condensation state (I want to estimate power consumption)?

[Ozone]

A drop in temperature and humidity.

The water vapour saturation point of air drops with falling temperature, causing the excess vapour to condensate.

If you can't/don't measure at least one of said conditions, the best way would be to heat it always, just to make sure.

For the duration, I think it depends on your application, and the deployment site.

The easiest way would be to measure/test it.

[GShim]

Thanks.

You wrote "If you can't/don't measure at least one of said conditions".

What does it mean?

I start a reading, and when it is ready (STATUS_REG) I read the data.

There is no register with error indication.

How do I know that the reading is valid, or not because of condensation?

[Ozone]

> There is no register with error indication.

> How do I know that the reading is valid, or not because of condensation?

Exactly.

You would need to gather that knowledge algorithmically, keeping track of values and evaluating the state.

Or simply use the "worst case" approach.

I think you need to evaluate the "use cases" (possibly occuring operating conditions) first, and decide how to deal with it.

Often, additional hardware is a no-go, and "econimcal aware" managers rather accept errors under fringe conditions.

[GShim]

Thanks.

Do you have any idea how long should the heater be active?

Just some rough number.

I am trying to estimate the power consumption.

It is a battery powered device.

[Ozone]

> Do you have any idea how long should the heater be active?

Not really.

But if ST does not specify data, I would create a test environment to produce condensation, and acquire data series (sensor values over time) to learn about the behaviour of the measured value.

Perhaps several sensor instances with different switch-on times in parallel (at once), assuring identical climatic conditions.

[GShim]

Thanks a lot.