Calculate dT/dt513
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Terp private msg quote post Address this user | |
| I would like to calcualte the time specific dT/dt value for the measured temperature profile over time. How can this be done in GroveStreams? |
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Trakk private msg quote post Address this user | |
| I may be looking for something similar. I have a stream from a thermostat logging on/off times and temperature. I want to be able to get the total on time each hour of the day. And the last temperature logged at those times. This way I can find out the overall efficiency (not scientifically) of how long it takes to cool. I could then use it to know when a filter needs to be changed (more or less often). Since I also track door open-close, I could use this same method to track door being left open and causing the unit to run more often. My data arrives with true/false for contact open closed for the door. And idle/cool (or heat) for on/off of cooling / heating. |
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MikeMills private msg quote post Address this user | |
| @Trakk I think this is what you want. If not, it should point you in the right direction. I created four streams: 1. Temp: Actual temperature readings with sample times. Samples are type Double. Regular stream. 2. Temp Sample Times: Derived regular stream. Type Long. Holds the Sample times of Temp stream so that we can find the deltas. Times are epoch millis. 3. Temp dt (millisecs): Derived regular stream. Type Long. Holds the change in sample times between samples. 4. Temp Profile Over Time: dT/dt. Regular stream. Type Double. dt is change in milliseconds. Screenshots. See the selected stream on the left for each:     Derivation is running about every 30 seconds per expression tree level so it took under 90 seconds to get the result after the temperature arrived. |
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MikeMills private msg quote post Address this user | |
| @Trakk "And the last temperature logged at those times." Getting the last temp for the Day or Hour is easy. Choose a Day, or Hour, cycle with the LAST function. This will return the last sample value for that cycle. You can choose Cycles and functions (min,max,sum,last, ...) in Dashboard widgets or in a derived stream expression. "I want to be able to get the total on time each hour of the day." I'm still thinking about this one... |
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