Accurate calibration of high current sensors
The power levels of electric vehicles, photovoltaic inverters, and energy storage systems continue to increase. Accurately monitoring the working status of the control system, especially the precise measurement of currents of tens or even hundreds of amperes in the system, is a new challenge faced by many engineers!
200W
Mobile phone fast charging
400KW
Electric vehicle fast charging
350KW
Photovoltaic inverter
When R&D engineers select current sensors from the market to be embedded in their products, they often worry about the performance and accuracy of the products, especially whether the system can meet the design requirements in various complex application scenarios. This requires the system to correct the collected data while maintaining sufficiently high reliability to truly reflect the changing current.
The figure below is a schematic diagram of a bidirectional DC-DC power supply module. The red circles in the figure are all current measurement sensors, which are used in conjunction with voltage measurement sensors to achieve accurate measurement of real-time power, efficiency and other parameters.
There are many methods for current measurement, each method has its own characteristics and is applicable to different occasions. Commonly used current sensors include sampling resistors, Hall, fluxgate, Rogowski coils and other types.
Precision sampling resistor
High Precision Fluxgate
Hall voltage
Rogowski coil
There are many factors in selecting current sensors, including AC and DC measurement, operating frequency range, dynamic performance, response speed, linearity, overload capacity, isolation and safety, size, installation and maintainability, etc.
A high-precision, high-current reference source is the basis for ensuring the accuracy of current sensor calibration and testing. However, engineers find it increasingly difficult to find a satisfactory current source:
On the one hand, the current range is large, and the accuracy of the ten-thousandth level is very challenging; on the other hand, the actual working conditions are often dynamic currents with a large fluctuation range, requiring both DC and AC and good accuracy for both large and small currents. In addition, the current standard sources on the market are expensive and have single performance, so they are usually not equipped in R&D departments.
Current sensor calibration and verification block diagram
Transformer to be tested
Keysight Technologies' APS series advanced power systems have a maximum current of 800A per unit, a reading accuracy of 0.04%, and built-in arbitrary waveforms that can output various waveforms such as sine waves, square waves, and swept frequencies. At the same time, the measurement energy of 200Ksa/s and 18-bit high-precision sampling has become the first choice for more and more milliohm and microohm precision resistor calibration, current transformer verification, superconducting material verification, fuses, relays, wiring harnesses, terminals, and other high-current, low-resistance tests.
During the shunt test, in order to avoid the temperature rise of the tested product caused by continuous high current, the APS advanced power system outputs 100A, 1mS current pulses. By setting the duty cycle, the average current is only 474mA. As shown below:
For more information, please watch the video
Video Demonstration 1
Video Demonstration 3