Wrong Reading of Voltage

[wahajmurtaza]

Hi, I am using your library to measure ac voltage only (modifying example code). I disconnected ac source during calibration as mentioned and even tried while being connected to ac source, I am getting values of more than 1000V while I have connected it to 220V AC source.

[Abdurraziq]

If your connection is not problematic then the possibility is in the sensitivity setting. Have you tried adjusting the sensitivity of the sensor through the setSensitivity() method? By default the value is 0.001. This value may not be the same between one sensor and another sensor. So please try with a different sensitivity value until the result is the same as a voltage source you use.

example

#include "ZMPT101B.h"

ZMPT101B voltageSensor(A0);

void setup()
{
  Serial.begin(9600);
  Serial.println("Calibrating... Ensure that no current flows through the sensor at this moment");
  delay(100);
  voltageSensor.setSensitivity(0.019);
  voltageSensor.calibrate();
  Serial.println("Done!");
}

void loop()
{
  float U = voltageSensor.getVoltageAC();
  Serial.println(String("U = ") + U + " V");
  delay(1000);
}

[wahajmurtaza]

I calibrated it using the setSensitivity() for 220v but when I switched to 150V it had some large inaccuracies. I am working on the problem and will let you know.

[Kingshahzad78]

Hi Dear, I had alot of trouble in using ZMPT101b concerning the different coding I downloaded and libraries too. But when I downloaded library and coding you wrote. Every thing is fine and going well now. Thanks for your efforts.

[Bbadru]

Hi dear, i'm using your example and during calibration i was getting 5.3 volts but when i put on the supply i was getting 19v instead of 220 volts according to my multimeter

[Bbadru]

i set my sensitivity to 0.002 and i got values close enough; but how can the sensitivity values be explained/ chosen. is it just random or is there a formula

[Abdurraziq]

i set my sensitivity to 0.002 and i got values close enough; but how can the sensitivity values be explained/ chosen. is it just random or is there a formula

In the simplest case you can use intuition 😁 by trying any value, and then start decreasing or increasing the value until you are sure that it is the right value.

But if you want to use a formula, I think the easiest method is to divide the value of the voltage you are measuring by the AC voltmeter between Vout and Vin.

But make sure that the AC voltmeter you are using has a good DC coupling capability so that only the AC voltage is measured in Vout. This is because the ZMPT module has a DC offset at its output so the zero point will shift approximately half of the VCC.

Sorry for taking too long to reply.

[Bbadru]

Thanks alot man

[BimoSora2]

I never got an exact value, the avometer says 233v but your default code says 197v

[Abdurraziq]

I never got an exact value, the avometer says 233v but your default code says 197v

Hi @BimoSora2 What board are you using? Unfortunately this library currently only supports 5V microcontrollers (eg Arduino UNO).

Have you tried this suggestion before? Here you need to determine the sensitivity, you can do it by trial error until the value is appropriate.