Question in regards to SGP30 Humidity Compensation

[bittailor]

Hi

I'm not sure this is the right place to ask questions, but I did not find another one.

My question is regard to the SGP30 Humidity Compensation (Set_humidity command).

In the example usage the Humidity Compensation is set after measuring the IAQ values just before sleeping for 1 second:

embedded-sgp/sgp30/sgp30_example_usage.c

Lines 82 to 95 in fab36ac

	err = sgp_measure_iaq_blocking_read(&tvoc_ppb, &co2_eq_ppm);
	if (err == STATUS_OK) {
	/* printf("tVOC Concentration: %dppb\n", tvoc_ppb);
	* printf("CO2eq Concentration: %dppm\n", co2_eq_ppm);
	*/
	} else {
	/* printf("error reading IAQ values\n"); */
	}
	/*
	* IMPLEMENT: get absolute humidity to enable humidity compensation
	* u32 ah = get_absolute_humidity(); // absolute humidity in mg/m^3
	* sgp_set_absolute_humidity(ah);
	*/

Intuitively I would have done it before measuring. What is the reason to do it afterwards or does it not matter when the Humidity Compensation is set?

Thanks and regards

[abrauchli]

Hi Franz Thanks for your question and your interest in our sensor. You're right, setting the humidity before measuring would be more fitting since the sensor will always use the last set value at the time of the measurement, but humidity changes are rarely so drastic, so for the SGP30 with 1Hz it practically won't matter, but it might for the SGPC3 in ultra-low power mode where sampling only occurs every 30s. Feel free to open a pull request to fix it. Kind regards Andreas On Mar 11, 2019 20:32, Franz Schnyder <[email protected]> wrote: Hi I'm not sure this is the right place to ask questions, but I did not find another one. My question is regard to the SGP30 Humidity Compensation (Set_humidity command). In the example usage the Humidity Compensation is set after measuring the IAQ values just before sleeping for 1 second: https://github.com/Sensirion/embedded-sgp/blob/fab36ac8b8d15f1eaf9328ddbf508024c09a85c7/sgp30/sgp30_example_usage.c#L82-L95 Intuitively I would have done it before measuring. What is the reason to do it afterwards or does it not matter when the Humidity Compensation is set? Thanks and regards — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub<#42>, or mute the thread<https://github.com/notifications/unsubscribe-auth/AANN8gbozyAWsfaAo7my9o7gQ_WQFQhGks5vVq8ggaJpZM4bpZL6>.

…

________________________________ Confidentiality: The information contained in this email message and all attachments transmitted with it is legally privileged and confidential information intended only for the use of the addressee. If you have received this email in error, please immediately notify us and delete this email and any attachments from your system. Thank you.

[bittailor]

Hi Andreas,
Thanks for the quick response.