Module can measure the positive and negative 5AMP, 20AMP , 30AMP 
Operating Voltage Range: 4.5V ~ 5.5V
Output voltage proportional to AC or DC currents
On-board power indicator
Nearly zero magnetic hysteresis
Factory-trimmed for accuracy
Extremely stable output offset voltage

Current Range: 5A
Current sensor chip: ACS712ELC-05A
Pin 5V power supply, onboard power indicator
The module can measure ±5A current, corresponding to analog output 185mv/A
When no detection current flows, the output voltage is VCC/2 

Current Range: 20A
Current sensor chip: ACS712ELC-20A
Pin 5V power supply, onboard power indicator
The module can measure ±20A current, corresponding to analog output 100mv/A
When no detection current flows, the output voltage is VCC/2 

Current Range: 30A
Current sensor chip: ACS712ELC-30A
Pin 5V power supply, onboard power indicator
The module can measure ±30A current, corresponding to analog output 66mv/A
When no detection current flows, the output voltage is VCC/2  

Note: ACS712 is based on the principle of Hall detection, please try to avoid the influence of magnetic field when using it.