Give sensors information about their own variables

[SRGDamia1]

Figure out a way to have a sensor figure out the metadata about its own variables. Currently that is stored in the variable objects, but it is also a property of the sensor's results passed to the variable via defines used in the specific variable constructors metadata. Right now there is no way for a sensor to know that the value in place 2 of its value array has the unit of meters. There's also no way to verify that someone doesn't try to create a variable erroneously linked to the value position of a sensor.

I'm not sure how to implement this. To store the information in the Sensor, each sensor would have to store a bunch of arrays of the metadata for each variable it can measure. And, because the same information is also a property of the variable itself - and variables need to store it since they could also be calculated and not linked to a sensor - storing the info in the Sensor object means it's stored twice.

Could the sensor initialization immediately create an instance of each possible variable and then place the pointers in the correct position in the variable pointer array store inside the sensor? Then, when a user wants to create a variable array, they could somehow get the pointer back out of the sensor object for the variables it created. Of course, that's a big change from how we've created the variable arrays and it means there are always a bunch of extra variable objects taking up space in memory even when the user has no use for them.

[neilh10]

Possible one way to think about it is attribute of a "Smart Transducer" - that is differentiating a sensor that translates from a physical quantity.

The Sensor (The "Input" Device) A sensor is a physical device that detects a change in a physical quantity (like heat, light, or pressure) and converts it into a signal that can be read by an observer or an instrument.
Output: Usually an electrical signal, but it can also be something simple like the expansion of liquid in a thermometer.
Possibly when digitized converted to a number - but uncalibrated.

The Transducer (The "Converter") A transducer is a broader term for any device that converts energy from one form to another. While a sensor is technically a type of transducer, a transducer can also work in reverse (converting electrical energy back into physical movement).
Output: One form of energy to another (e.g., Electrical to Mechanical)
Possibly convert an uncalibrated number to a calibrated number with units - with a lot of other meta information, serial number, etc in specific format.

Turns out there is a Transducer Electronic Data Sheet - TEDS IEEE 1451
https://www.nist.gov/el/intelligent-systems-division-73500/ieee-1451
https://www.nist.gov/el/intelligent-systems-division-73500/transducer-electronic-data-sheet

The other challenge with this, when and who to access the meta information. So a bit of a challenge :)