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Fluctuating ADC Reading for 4-20mA Pressure transducer input

Discussion in 'Microcontrollers, Programming and IoT' started by BHARGAV SHANKHALPARA, Aug 2, 2018.

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    Nov 6, 2013

    I am working on one project of water pressure measurement, in which i used pressure transducer which gives me output between 4-20mA Current form.

    I am using one 250 ohm resistance to convert current into voltage, and than i give this voltage to ADC of arduino UNO channel 0 (A0).

    ADC reading is continuously fluctuating up to 10 decimal numbers.

    I have also check by connecting multi-meter and measure sensor current reading, for particular pressure. but current reading is stable (even not fluctuate 1 or 2 points.)

    also i have checked voltage value after 250 Ohms +Ve and ground. converted voltage is also showing very stable.

    but why ADC reading is fluctuating..?

    i am using arduino uno, i doesn't have any changes in AREF, AVCC etc...

    please suggest effective solution,

    Thank in advance.

    My code is as follow

    const int analogInPin = A0; // Analog input pin that the potentiometer is attached to

    int sensorValue = 0; // value read from the pot

    void setup()
    // initialize serial communications at 9600 bps:

    void loop()

    // read the analog in value:
    sensorValue = analogRead(analogInPin);

    // print the results to the Serial Monitor:
    Serial.print("Reading: ");


    Attached Files:

  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Your measurements with a multimeter may not show rapid changes. Have you tried looking at the voltage using an oscilloscope or even your multimeter on an AC range?

    What effect sites placing a capacitor (say 1uF) across the resistor have?

    If you connect the ADC input to a voltage divider across the power supply, do you get a more constant reading?
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