Table of Contents
1. Current Sensor Types and Characteristics
A variety of methods are used in our daily lives to measure and monitor current to contribute to energy conservation and ensure our safety and security.
The figure below shows the most commonly used current sensor types.
This article describes different types of current sensors and their characteristics.
2. Shunt Resistor Current Sensor
A shunt resistor current sensor is a current sensor that uses an amplifier (signal amplifier circuit) to amplify the voltage generated at each end of a shunt resistor inserted in the current path to measure current.
Its low cost and high-accuracy current detection make it a popular choice. Although as little as a few tens of amperes flowing through the shunt resistor could lead to the problem of power loss, this can be solved by pairing a shunt resistor with as low impedance as possible with a high-accuracy operational amplifier.
It also provides higher accuracy than magnetic current sensors described below, and is not easily susceptible to external disturbing fields. ABLICs operational amplifiers can be used with this type of method.
3. Magnetic Current Sensors
Magnetic current sensors are non-contact current sensors that measure current by measuring the magnetic fields generated by flowing current. Hall effect ICs or other magnetic sensors are used to measure magnetic fields.
A magnetic current sensor either comes with or without a magnetic core.
Core Current Sensor
A core current sensor is a magnetic current sensor with a magnetic core.
A magnetic sensor IC is inserted in the gap of the magnetic core and measures the magnetic fields generated around the current line through the magnetic core.
Since the resistance in the current line of this method can be reduced, power loss can also be reduced. However, the need for a magnetic core raises costs. It also increases the mounting area.
Coreless Current Sensor
A coreless current sensor is a magnetic current sensor that does not use a magnetic core and is configured only of a coreless current sensor IC.
A coreless current sensor IC directly measures the magnetic field generated by current accumulated in the IC.
Since this method does not use a magnetic core, the mounting area can be smaller. However, rising impedance in the path of current accumulated in the IC causes power loss. It is also susceptible to external disturbing fields and will require shielding in some environments.
4. Comparing Sensor Types
The ideal current sensor depends on the application.
| Shunt resistor current sensor | Core current sensor | Coreless current sensor | |
|---|---|---|---|
| Current detection range | For low current detection | For high current detection | For low to medium current detection |
| Detection accuracy | High accuracy detection of minute current | Strong magnetic fields aggravate accuracy | High-accuracy detection is a challenge |
| Power loss and heat | Measuring high current generates heat | Generates less heat than other methods | Measuring high current generates heat |
| Tolerance of external disturbing fields | Not susceptible to external disturbing fields | Susceptible to external disturbing fields, countermeasures required | Susceptible to external disturbing fields, countermeasures required |
| Mountability | Easy to mount, but adds a second key part | Large core causes space constraints | Easy to mount and only one key part |
5. Zero-drift Amplifiers Recommended by ABLIC
Automotive operational amplifiers
| S-19630A | High-withstand voltage, High-accuracy, Zero-drift amplifier, Rail-to-Rail |     | |
| S-19611A | Low voltage operation, Zero-drift amplifier, Rail-to-Rail | |
Operational amplifiers for general use
| S-89630A | High-withstand voltage, High-accuracy, Zero-drift amplifier, Rail-to-Rail | | |
| S-89713 | Low voltage operation, Zero-drift amplifier, Rail-to-Rail | |