[lm-sensors] [PATCH v2] hwmon: Honeywell Humidicon HIH-6130/HIH-6131 humidity and temperature sensor driver

Iain Paton ipaton0 at gmail.com
Wed Jun 27 09:41:18 CEST 2012


On 06/22/2012 03:34 PM, Guenter Roeck wrote:

>> +	 * Response time for the sensor is measured in seconds, so we have
> 
> in seconds ?

So, how to word it then...  In the datasheets words, "The measurement cycle 
duration is typically 36.65 ms for temperature and humidity readings."

However we also have

Table 2. Humidity Performance Specifications
Characteristic Condition                Min  Typ  Max  Unit
Response time  airflow minimum 20 l/min  –    6    8    s


Table 3. Temperature Performance Specifications
Characteristic Condition                Min  Typ  Max  Unit
Response time  1/e slow moving air       5    -    30   s

So although we can run a measurement in around 40ms it will take the sensor longer
to react to a change.

I agree this needs to be clear, or there's no point to the comment. Just that 
you're asking suggests it's not clear enough. Suggestions ?


How about this:

While the measurement can be completed in ~40ms the sensor takes much longer to react
to a change in external conditions. How quickly it reacts depends on airflow and other
factors outwith our control.
The datasheet specifies maximum 'Response time' for humidity at 8s and temperature at
30s under specified conditions.
We therefore choose to only read the sensor at most once per second. This trades off
pointless activity polling the sensor much faster than it can react against better 
response times in conditions more favourable than specified in the datasheet.

Too much ?

Iain




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