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

Guenter Roeck linux at roeck-us.net
Wed Jun 27 16:27:33 CEST 2012


On Wed, Jun 27, 2012 at 07:41:18AM +0000, Iain Paton wrote:
> On 06/22/2012 03:34 PM, Guenter Roeck wrote:
> 
> >> +	 * Response time for the sensor is measured in seconds, so we have
> > 
> > in seconds ?
> 
Hi Iain,

How about "Response time for the sensor to react to changes in external
conditions is several seconds, so we have ..."

> 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.
> 
Sounds like an excellent note to add to the Documentation file.

Thanks,
Guenter




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