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Average statistical function


  • Hi, I am using the following to get the temp from an NTC

    T = t1.past(MINUTE).average;
    
    THERMISTORNOMINAL = 10000;
    
     // temp. for nominal resistance (almost always 25 C)
    TEMPERATURENOMINAL = 25;
    
    // The beta coefficient of the thermistor (usually 3000-4000)
    BCOEFFICIENT = 3435;
    
    // the value of the 'other' resistor
    SERIESRESISTOR = 14910;
    
    average = 1023.00 / T  - 1.00;
    
    average = SERIESRESISTOR / average;
    
    steinhart = average / THERMISTORNOMINAL; // (R/Ro)
    steinhart = Math.log(steinhart); // ln(R/Ro)
    steinhart /= BCOEFFICIENT; // 1/B * ln(R/Ro)
    steinhart += 1.0 / (TEMPERATURENOMINAL + 273.15); // + (1/To)
    steinhart = 1.0 / steinhart; // Invert
    steinhart -= 273.15; // convert to C
    
    return steinhart ;
    

    Trouble is that when even for the past one hour where there is **NO **t1 value received, the average function still returns the average based on whatever was stored earlier. I was expecting that in case of no data, the average function based on time would return a NULL.

    Any thoughts / suggestions ?