I would like to know the best way to tag a point that shows the error in zone temperature compared to the zone's effective setpoint, I have come up with this list:

1. point
2. zone
3. air
4. temp
5. deviation
6. sensor
7. kind: "Number"
8. unit: "°F"

I have been having some debate in substituting the following with:

1. Substitube deviation with delta
2. Substitute unit: "°F" with unit: "Δ°F"

What are everyone's thoughts?

The "delta" tag is the stndard Haystack tag to indicate a difference between points. Using a tag instead of an engineering unit makes it queryable in Axon and other functions.

By convention "delta" is the difference between two sensors, offering a change value across two different inputs.

I suppose from a design standpoint, my question would be what do you mean by "error in zone temperature"? Does this mean you have a setpoint, and this is the +/- deviation from that setpoint? If so, does this really need to be a point rather than a calculated value?

My 2 cents would be that this point would not need to be tagged.... as you already tagged setpoint and temperature... the haystack server should be able to tell you what's the difference between the two. It's a calculated value.

Existing convention is that delta is difference between two different sensors.

This sounds more like the delta between sp and sensor for the same logical measurement (zone temp). It feels like the term delta for that situation is not semantically the same with previous usage.

So I would vote for something more like deviation (or maybe spDeviation)