DS18B20 temperature sensore calibration

[bitzy]

hello.
i have a bunch of ds18b20 sensors attached to my raspberry that read various temperatures on my hydronic system and the room temperature ...
the problem i that when put together, to read the same temperature, the deviation of readings is high from 1 sensor to another. i try to do a calibration like in this site https://www.instructables.com/Calibrati ... duino-UNO/.
the only way i could do this was to create a virtual temperature sensor that will display the calculated temperature from this script:

Code: Select all

return {
    on = {
        devices = { 'EXTERIOR_raw' } -- the physical temperature sensore
    },
    execute = function(dz, device)
        -- Calibration values
        local rawHigh = 97.3 -- Raw temperature read at the boiling point of water
        local rawLow = -0.5 -- Raw temperature read in the ice bath
        local rawRange = rawHigh - rawLow

        local referenceHigh = 99.2 -- Temperature for the boiling point of water at atmospheric pressure
        local referenceLow = 0 -- Temperature for the Triple-point bath
        local referenceRange = referenceHigh - referenceLow

        -- Function to perform temperature correction and rounding
        local function correctTemperature(inTemp)
            local corrected = (((inTemp - rawLow) * referenceRange) / rawRange) + referenceLow
            return math.floor(corrected * 10 + 0.5) / 10 -- Round to 1 decimal place
        end
        
        -- Updating the virtual sensor with the calculated value
        if (device.name == 'EXTERIOR_raw') then
            local inTemp = device.temperature
            local correctedTemp = correctTemperature(inTemp)
            dz.devices('EXTERIOR').updateTemperature(correctedTemp)
        end
    end
}

the problem is i need to do this for every sensor i have. and are couple of them (7 for the moment and more are to come) witch lead to a lot of scripts and a lot of new sensors to display.
is there a simpler way to use this type of calibration? some type of advanced calibration directly on the physical sensor?

[bitzy]

with the help of my new best friend (ChatGPT) 1 simplification down
1 script to rule them all

Code: Select all

-- Define the mapping between physical and virtual sensors
local sensorMapping = {
  ['EXTERIOR_raw'] = 'EXTERIOR',
  ['Cam_Centrala_raw'] = 'Cam_Centrala',
  ['Vana_Amestec_raw'] = 'Vana_Amestec',
  ['Tur_raw'] = 'Tur',
  ['Retur_raw'] = 'Retur',
  ['Baie_raw'] = 'Baie',
  ['Puffer_raw'] = 'Puffer',
  -- Add more mappings as needed
}

return {
  on = {
    devices = {
      'EXTERIOR_raw',
      'Cam_Centrala_raw',
      'Vana_Amestec_raw',
      'Tur_raw',
      'Retur_raw',
      'Baie_raw',
      'Puffer_raw',
      -- Add more physical sensor devices here
    }
  },
  execute = function(domoticz, device)
    -- Calibration values for each physical sensor
    local calibrationValues = {
      ['EXTERIOR_raw'] = { rawLow = -0.5, rawHigh = 97.3, referenceLow = 0, referenceHigh = 99.2 },
      ['Cam_Centrala_raw'] = { rawLow = -0.3, rawHigh = 98.3, referenceLow = 0, referenceHigh = 99.2 },
      ['Vana_Amestec_raw'] = { rawLow = 0.7, rawHigh = 98.3, referenceLow = 0, referenceHigh = 99.2 },
      ['Tur_raw'] = { rawLow = 0.7, rawHigh = 98.7, referenceLow = 0, referenceHigh = 99.2 },
      ['Retur_raw'] = { rawLow = 0.3, rawHigh = 98.8, referenceLow = 0, referenceHigh = 99.2 },
      ['Baie_raw'] = { rawLow = 0.8, rawHigh = 98.6, referenceLow = 0, referenceHigh = 99.2 },
      ['Puffer_raw'] = { rawLow = 0.9, rawHigh = 98.9, referenceLow = 0, referenceHigh = 99.2 },
      -- Add calibration values for more physical sensors here
    }
    
    -- Get the corresponding virtual sensor
    local virtualSensor = sensorMapping[device.name]
    
    -- Check if the virtual sensor exists in the mapping
    if virtualSensor then
      -- Get the calibration values for the current physical sensor
      local calibration = calibrationValues[device.name]
      local rawLow, rawHigh, referenceLow, referenceHigh = calibration.rawLow, calibration.rawHigh, calibration.referenceLow, calibration.referenceHigh
      
      -- Read raw temperature from the physical sensor
      local rawTemperature = tonumber(device.temperature)
      
      -- Calculate calibration values
      local referenceRange = referenceHigh - referenceLow
      local rawRange = rawHigh - rawLow
      local correctedValue = (((rawTemperature - rawLow) * referenceRange) / rawRange) + referenceLow
      
      -- Round the corrected value to the nearest decimal place
      correctedValue = math.floor(correctedValue * 10 + 0.5) / 10
      
      -- Update the corresponding virtual sensor with the rounded calibrated value
      domoticz.devices(virtualSensor).updateTemperature(correctedValue)
    end
  end
}

i hope that when my new best friend will take over the world, will forget that i made him an idiot !!

now, someone know some more simplification? a way to get rid of all those virtual sensors?

[Kedi]

Why not ask your 'new best friend' ?

[bitzy]

i already asked and he sent me to the forum cause he do not know (at this point of his live is more an A and less of an I ).

(and u sound a little bit jealous )

[willemd]

My temperature sensors show an "adjustment" field when I click "edit" on the sensor icon. I assume this is a calibration value?

[bitzy]

if your sensor need to read a large range of temperatures (for example between -10 and 40 degrees) and u use that calibration button at a certain temperature, your sensor will be way off when go below or above the temperature u calibrated so i think u are better with the factory calibration and not using that.

[Kedi]

I think that the calibration value is for ALL values that are send to Domoticz, positive and negative values.
It is just a correction of the value send to Domoticz with that amount.

[bitzy]

i tryied to calibrate them with the help of that button.i did like this: put all the sensores together in a glass with ice and water and adjusted them all to show the same value. all great.
then i remove them from the water and let them all side by side to read the room temperature and the diferences betweenn them were bigger then without the calibration so ...

[Kedi]

Are all ds18b20 set to the same resolution?

[HvdW]

If you're using dzvents to display the values it's easy.
Adjust the received value in the script.
You can do it either by adding or substracting a value or by adding or substracting a percentage, depending on the deviation under different temperatures.

[kimot]

Connect sensors to ESP running ESPeasy and you can calibrate each sensor individually before send data to Domoticz....

[simat]

Or maybe the DS18B20's are fake, there are loads of non genuine ones on Aliexpress.
https://github.com/cpetrich/counterfeit_DS18B20