### What could be practical appliance of Expert virtual sensor in Aranet cloud?

aranet-techsupport

Posted: 14.06.2021 10:36

Modified: 06.10.2024 09:13

You can select an

*Expert*template when creating a Virtual sensor in the Aranet cloud:

This formula represents calculations to be made with measured data of

**up to 10 sensors**. All input sensors must have the same*metric*. The result of calculations will have the same*metric*as input sensors.Formula variables are:

- input sensors measurement,*x(t)**unit*is- slope, a real number in the range of**k***-1e+10*to*1e+10;*- offset, the same**b***unit*as input sensor;- number of sensors,**n***min = 1*,*max = 10*;- normalizing factor, a real number in the range of**m***-1e+10*to*1e+10,***must not be equal to 0**.

Indeed,

*Offset, Average and Sum*are special cases of*Expert*formula.Simple implementation of this formula can give you a more precise value of, f.e. average temperature in the room. Let's take for example a room where 3 pcs. of individually calibrated temperature sensors are placed:

Sensors offsets values were obtained experimentally by comparing measured data with laboratory-grade thermometer data.

Sensor #1 has offset

**b2 = -0.8°**and is placed near Air Conditioner, so its measurements are affected by cold airflow and should be corrected by slope, let's say**k2 = 1.12.**Sensor #2 has offset

**b1 = 0.6°**and is placed on the sunny side of the room, so in the daytime, its measured temperature is affected by sun radiation and should be corrected by slope, let's say**k1 = 0.914**.Sensor #3 has offset

**b3 = 0.7°**and is placed in the centre of the room and its measurements are not affected by external influences, so the slope is**k3 = 1**.In this case consider

**m = n = 3**, last measurements readings are visible in the input column:**x1 = 23.5**,**x2 = 24.7**,**x3 = 23.9**. And calculated virtual sensor out is**24.4°.**This value can be considered as rooms average temperature.erensts

Posted: 09.07.2021 15:39

As outdoors is very hot and I do not have aircon, I have created a virtual sensor that measures delta between indoor and outdoor temperature and if it goes below or above the thresholds I get a notification to open or close the window to preserve room temperature as low as possible.

Virtual sensor to create delta - now outdoors is close to 34 degrees Celsius hot and the room is 28.9, so I use -1 as a multiplier to calculate the delta.

The second step is Alarm based on the virtual sensor:

Result - if the outside is hotter than indoors at least 2 degrees I am notified to close the window and preserve the room in mild condition. when during evening temperature drops below room temperature I get notifications to open the window and cool the room a natural way.

And this is how do I see it in notifications - Alarm is active as delta is above 2 degreesniels

Posted: 12.01.2024 10:23

The constraint that the formula must yield the same metric as the sensors seems arbitrary. Examples:

- I could use your infrared sensor to calculate temperature; that would tranform W/m2 into Celcius.
- I could use a multispectal light sensor (hacking in a transmitter of yours for each spectral channel) to estimate the biomass of a crop (turning W/m2 into kg/m2).
- I could use your UV sensor to inform about the recommended maximum time of unprotected exposure (turning W/m2 into hours and minutes).

Why not provide a simple text box to type in the metric resulting from the formula? That's even way easier to implement than the formula itself!

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