Hello, > > integration time is in seconds; it controls the measurement > > time and influences the gain of a sensor > > > > used by adjd_s311, tsl4531 > > the following drivers have similar controls: > > * tsl2563 (integration time is controlled via CALIBSCALE among other things) > > * tsl2583 (has integration_time device_attr, but driver doesn't use channels yet) > > * tsl2x7x (has integration_time attr) > I know this has come up before (and I'm not actually expressing oposition > to this going into info_mask) but could you sumarise the arguments for why > this property cannot be covered by calibscale or scale? > I'd like to have a little stronger argument for the patch description in Git. sounds good; I'd add: > There are two typical ways that scaling is implemented in a device: > 1) input amplifier > 2) reference to the ADC is changed. > These both result in the accuracy of the ADC varying (by applying it's > sampling over ta more relevant range). > > Integration time is a way of dealing with noise inherent in the analog > sensor itself. In this case a mixture of Photon noise and device specific > noise. Photon noise is dealt with by either improving the efficiency of > the sensor, (more photons actually captured) which is not easily varied dynamically, > or by integrating the measurement over a longer time period. Note that this > can also be thought of as an averaging of a number of individual samples > and is infact sometimes implemented this way. altering integration time implies that the duration of a measurement changes and the user of the device may be interested > Hence it makes sense to distinguish between integration time and simple > scale. In some devices both types of control are present and whilst they > will have similar effects on the amplitude of the reading, their effect > on the noise on the measurements will differ considerably. integration time may or may not have an impact on the range of values measured both characteristics cannot be expressed with scale/calibscale in a satisfying way let's see if further comments come up, and I'll repost please note that there is a fix for the adjd_s311 driver posted which you may want to fast-feed to Greg thanks, regards, p. -- Peter Meerwald +43-664-2444418 (mobile) -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
