Is there an app note or other documentation related to how/when to appropriately use the heater bit on the HTS221? Regards, Regards,

[Eleon BORLINI]

Hi @tidd​ , there is some explanation for the heater usage in HTS221 in the datasheet, p. 23.

Case 1, Condensation issue: The Heater bit (CTRL_REG2 (21h)) is used to control an internal heating element, that can effectively be used to speed up the sensor recovery time in case of condensation. The heater can be operated only by an external controller, which means that it has to be switched on/off directly by FW. Humidity and temperature output should not be read during the heating cycle; valid data can be read out once the heater has been turned off, after the completion of the heating cycle. 

Case 2, Self-test: The heater network is necessary, after a long exposure to humidity, to dry fast the MEMS or in the Self-Test mode to check the functionality of the device and connection between ASIC and MEMS. During the self test a current flows in the heater, heating and consequently drying the sensing capacitor. In this condition a variation in relative humidity has to be detected if the device works correctly.

Regards

[tidd]

Hi @Eleon BORLINI​ ,

Thanks for the answer; however:

1. Much of the wording you reference is actually not in the data sheet on page 23 that you reference?
2. Either way, this doesn't address my original question. I am looking for guidance on when to turn on the heater, e.g. at a specific humidity value or after a specific humidity rate of change?
3. And/or do you always turn on at boot?
4. And also, since you can't read temp/humidity when it is on, how long to turn on, in other words, what is the proper length of a heating cycle?

Regards

[tidd]

Hi @Eleon BORLINI​ 

Do you have any more information regarding my 4 questions above?

Regards,

[Eleon BORLINI]

Hi @tidd​ ,

1.Much of the wording you reference is actually not in the data sheet on page 23 that you reference?

--> Case 2 is not reported extensively on the ds but it can be shared.

2. Either way, this doesn't address my original question. I am looking for guidance on when to turn on the heater, e.g. at a specific humidity value or after a specific humidity rate of change?

--> There is not a specific recommendation on when to turn on the heater: when the range limits are exceeded or when humidity stays high (above 90%) for long time (hours), and it is not falling down when the environmental conditions are changing, it is recommended to turn on the heater for some minutes.

3. And/or do you always turn on at boot?

--> No, it is not necessary except from you are storing your device in an environment with very high humidity and for long inactivity periods

4. And also, since you can't read temp/humidity when it is on, how long to turn on, in other words, what is the proper length of a heating cycle?

--> Recommended heating cycle is a few minutes, depending on the environmental conditions.

Regards