ACS711EX Varying wildly

I am using a ACS711EX Current Sensor and the current is varying wildly (amperage of 12 read steadily by a multi meter but the sensor returns values between 11 and 12.5). I am wondering if this is an issue with calibration or the sensor itself? Any ideas how to troubleshoot this?

This is my Arduino code, with VCC being 3.3 = currentSensor(analogRead(curSens1));

float currentSensor(float CS_Vout)
  CS_Vout = map(CS_Vout, 0, 1023, 0, 3.3);
  float c = 73.3*(CS_Vout/VCC_Teensy)-36.7;
  return c;
}//end current sensor



The typical output error of that current sensor at room temperature is ±4%, and it looks like you are getting about that or slightly worse. You might consider implementing additional data processing like a running average, which could help you get closer to the actual current measurement.