The most common type of sensor in power measurement and control systems is the current sensor, primarily used to measure current in circuits to prevent accidents caused by overcurrent. Therefore, the selection of a current sensor is crucial for measurement and control systems. So, what are the main characteristic parameters to consider before selecting a current sensor?
The standard rating IPN and rated output current ISN refer to the standard ratings that can be tested by the current sensor. It is expressed by the effective value (Arms). The value of IPN depends on the sensor product model. ISN refers to the rated output current of the current sensor, typically 100~400mA, although this may vary for some models.
The power supply voltage VA of a current sensor refers to the power supply voltage of the current sensor, which must be within the specified range. Furthermore, the power supply voltage VA of a current sensor is further divided into a positive power supply voltage VA+ and a negative power supply voltage VA-. Exceeding this range will cause the sensor to malfunction or reduce its reliability.
The measurement range, Ipmax, refers to the maximum current value that the current sensor can measure. The measurement range is typically higher than the standard IPN rating. It should be noted that the supply voltage VAmin of a single-phase current sensor is twice that of a two-phase current sensor, therefore its measurement range is higher than that of a two-phase current sensor.
Overload capacity of the current sensor. If the current is overloaded, the primary current will still increase outside the measurement range. The duration of the overload current may be short, and the overload value may exceed the current sensor's allowable value, but it will not damage the sensor. Accuracy of the Hall effect current sensor depends on the standard rated current IPN. At +25°C, the measurement accuracy of the current sensor is affected by the primary current. When calculating accuracy, drift current, linearity, and temperature drift must be considered.
Offset current (ISO), also known as residual current or residual current, is primarily caused by the unstable operating state of Hall elements or operational amplifiers in electronic circuits. When a current sensor is generated, the offset current is minimized at 25°C and IP=0, but a certain amount of offset current will be generated as the sensor leaves the production line. The accuracy mentioned in the product technical documentation takes into account the effect of the increased offset current.
Linearity determines how proportional the current sensor's output signal (secondary current IS) is to the input signal (primary current IP) within the measurement range. Temperature drift offset current ISO is calculated at 25°C. ISO changes as the ambient temperature around the Hall electrodes changes. Therefore, it is important to consider the maximum variation in the current sensor's offset current ISO.
