The operation of 4-terminal current sensor

4-terminal current sensor is the element which can convert current into voltage in a circuit.

A circuit is opened due to connecting to the current terminals (A1 and A2 in the figure A). The current goes through the terminal resistor (r1), the current sensing resistor (R) and another terminal resistor (r2) in the left picture. Then, the same voltage generates between terminal B1 and terminal B2 as well as at the both ends of the current sensing resistor. This voltage enables to detect the flowing current.

current [I] = voltage [V] / current sensing resistance [R]  

Though voltage generates at the both ends of terminal resistors in a current circuit, it is not included in a voltage sensing circuit so it need not be considered. Each terminal resistor (r3 and r4) is quite small related to impedance in a voltage sensing circuit, so it is possible to measure the current accurately without any consideration about resistance.

Note1: YDS’s 4-terminal current sensor consists of the current circuit, the current sensing resistor and the terminal resistor. Please consider the terminal resistance added due to the circuit design. The current sensing resistance is showed in the part number.

Note2: If the voltage terminal and the current are connected like figure B, the circuit doesn’t work accurately. Please do connect the voltage terminal and the current independently. If you need 2-terminal sensor on the land, we can serve specific resistors with low resistance for 2-terminal sensor.