There are various types of variable frequency drive Hall current sensors used to monitor AC or DC currents, which are required for many applications in industrial, automotive, and domestic fields. Below, we introduce several methods of current sensing:

1. DC Sensing Variable Frequency Drive Hall Current Sensor:

   DC sensing relies on Ohm's Law. By arranging parallel resistors with the system load, a voltage proportional to the system load current is generated across the parallel resistors. The voltage across the branch can be measured using a differential amplifier, such as a current shunt amplifier, operational amplifier, or differential amplifier. This method is typically used for load currents <100A.

2. Indirect Current Sensing with Variable Frequency Drive Hall Current Sensors:

   Indirect current sensing depends on Ampere's Law and Faraday's Law. By placing a loop around a current-carrying conductor, a voltage proportional to the current is induced in the loop. This method is used for load currents between 100A and 1000A.

1. Low-Side Current Sensing:

   This involves a low input common-mode voltage. Low-side current sensing connects the sensing resistor between the load and ground. This is advantageous because the common-mode voltage is close to ground, considering the use of a single power supply and rail-to-rail input/output operational amplifiers. The load is powered by a single supply, and the resistor is grounded. However, the drawback of low-side sensing is its potential interference with the system's ground potential and its inability to detect load shorts.

2. High-Side Current Sensing:

   High-side current sensing connects the sensing resistor between the power supply and the load. High-side sensing is preferred because it directly monitors the current supplied by the power source, allowing for the detection of load shorts. The test amplifier's input common-mode voltage range must accommodate the load supply voltage. The output is then measured by the current sensing device, with the load grounded.

3. Current Transformer (CT):

   A current transformer (CT) is a transformer used to measure current. CTs are widely recognized sensors for large current solid-state energy meters today. They can measure extremely high currents with minimal power consumption. They are also very useful for measuring or monitoring high currents, high voltages, and high-power circuits. They are used in various power systems, such as power supplies, motor control, and lighting control.