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-   -   SENSOR_DEFINITION - User Defined (http://www.rdmprotocol.org/forums/showthread.php?t=1077)

hamish October 28th, 2010 10:18 AM

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At LDI, I found a responder with a user defined Unit (Table A-13 Manufacturer-Specific Units) So far so good. What appears to be missing in respect of this, is a 'SENSOR_UNIT_DESCRIPTION' PID.

Reading ahead, some consideration should also be given to a 'SENSOR_TYPE_DESCRIPTION' PID. (Table A-12 Manufacturer-Specific Sensors)

This point is not irrelevant to the 'RPM' unit issue that keeps coming round.

I've not yet worked on a possible format for such PIDs, although I'd be happy to do so. Please discuss, comment so on and so fourth.

prwatE120 October 28th, 2010 11:27 AM

My preference would be to get the necessary units added to our existing list, as we already have a good number already defined, so hopefully there is only ever a small need for really manufacturer specific ones. Also, the two or three that have already been suggested have universal application.

ericthegeek October 28th, 2010 01:21 PM

From what I've seen, using the string in "SENSOR_DEFINITION" works well enough. You can include the human readable units in that string. I my controller, when I see a mfg specific Type or Unit, I just display it as a unit-less number.

The "Signal Strength (dBm)" shown in the attached graphic is a good example. I've also seen it done with "Lamp Blower RPMs". The user gets the information they need.

Pedantic: For dBm, I believe a type of SENS_POWER would be appropriate. dBm is a power ratio relative to 1 miliwatt.

hamish October 29th, 2010 05:31 AM


So far, I have done fairly much as much as you have you have suggested and to a point it works. The 'well enough' part is what concerns me. My problem here is that I can not foresee what units I should be searching for. Would the addition of a PID(s) not be a far more elegant solution? What would be the disadvantage of such an addition?

The addition of PID(s) would circumvent the problem of non SI units being added to the list of pre-defined units, which in turn lead to the flood gates of imperial and arbitrary units being declared.

By the by, I've only just figured that DB is an IEC and not an SI unit, being a ratio rather than a quantitative measurement. Something new every day eh!

ericthegeek October 29th, 2010 09:27 AM

I don't object to the PIDs being added. It's just that getting PIDs added takes a long time. In the mean time "Well Enough" will work, it's just sub-optimal.

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