Knowledge
Oscilloscope Current Measurement Core Technology
There are three common techniques for oscilloscopes to measure current, using shunts (serial resistors), current transformers, and current probes. All three methods require the measured current to pass through the measuring sensor, which is invasive. Among them, the current probe can complete the measurement without disassembling the wire, which is the least invasive technology, and the ETA56053A current probe is a representative product with excellent performance, and its application advantages are particularly prominent. This article will briefly explain the core limitations of the first two technologies, focusing on the principles, usage and optimization techniques of ETA56053A current probes.
Core Limitations of 1. Common Current Measurement Techniques
1. Shunt (serial resistor)
As a traditional measurement method, the use of shunt has obvious disadvantages: it needs to be designed and installed Secondary specialized school the gate of the circuit or test device, which is highly invasive, and needs to be weighed between serial resistance and measurement sensitivity, which is easy to affect the performance of the original circuit; Its bandwidth is limited by its own internal inductance and capacitance. Even if the bandwidth of the derived coaxial shunt is improved, its volume is much larger than that of the traditional flat shunt, and its size is proportional to the maximum rated current, adaptability is limited.
2. Current transformer
Using the principle of magnetic induction, the measured current wire needs to pass through the ferrite core, some products although the use of separate magnetic core to facilitate wire insertion, but still need to disassemble the wire operation.
3. Core advantages of current probe
With the split core geometry, the current probe can be directly installed into the current-carrying conductor without disassembling the wire, making it easy to operate and minimally invasive. The ETA56353A current probe has both an AC/DC coupling function and is adapted to a wider scene, and is a preferred device for current measurement.
二、ETA56053A current probe details
1. Basic parameters and core design
ETA56053A is the 1 high-performance AC/DC current probe with wide range and high bandwidth characteristics. It can accurately measure 0.1 A- 50A of current with DC-100MHz bandwidth coverage and can meet the needs of most industrial testing and electronic research and development scenarios. The core design highlight is the split ferrite core, which can be quickly sleeved into the current-carrying wire without dismantling the circuit, which greatly improves the measurement efficiency and avoids interference with the original circuit.
2. Working principle
The ETA56053A uses a hybrid measurement technology that combines the advantages of Hall-effect devices and current transformers to achieve accurate measurement of full-band signals:
● Relies on Hall-effect sensors in the core gap for DC current and low frequency AC signals. Under a reasonable bias voltage, the sensor will produce an output current proportional to the magnetic flux in the magnetic core, and the current will drive the feedback winding after amplification, so that the magnetic core is in a zero magnetic flux state. At this time, the current of the feedback winding accurately corresponds to the measured current;
● For high-frequency AC signals, because the output of the Hall effect sensor will attenuate with the increase of frequency, the feedback winding will switch to the current transformer mode to ensure the accuracy of high-frequency signal measurement;
● Finally, the induced current is converted into a voltage signal through the output terminal and transmitted to the oscilloscope for reading.
3. Oscilloscope adaptation and operation settings
The ETA56053A supports the standard BNC interface, which can be seamlessly adapted to various types of oscilloscopes. The ETA56053A has two sensitivities of 1V/A and 100mV/A respectively). When in use, the proportional coefficient of the corresponding channel is adjusted to directly convert the voltage signal into amperage display without manual calculation.
At the probe control end, two core controls, degaussing and auto-zero, are integrated, and these two core controls are integrated into a button:
● degaussing function: can eliminate the residual magnetic flux in the magnetic core, it is recommended to perform before important measurements to ensure measurement accuracy;
● Auto-zero control: When there is no current, the offset of the probe output can be calibrated to zero volts to avoid zero error. In addition, the dialog box can also display the core specifications such as the rated current, bandwidth and sensitivity of the probe, which is convenient for users to check the parameters in real time.
三、ETA56053A optimization skills
Improve the sensitivity of small current measurement
When measuring a small current, you can wind a few more turns of the measured wire on the core of the ETA56053A. The more turns, the higher the sensitivity of the probe (for example, when winding 4 turns, the sensitivity can be increased by 4 times). Note that the turns factor needs to be manually entered into the oscilloscope's "Rescale" setting; at the same time, the probe's insertion impedance increases in proportion to the square of the number of turns (16 times the impedance increases at 4 turns), but the effect on the measurement result is negligible due to the very low impedance drop in small current measurements.
四、 Universal Adaptability of ETA56053A
The ETA56053A is not only suitable for special oscilloscopes, but also can be used as a third-party probe to adapt various general-purpose oscilloscopes without proprietary interfaces. Its own independent power supply, degaussing control and DC offset adjustment function, no need to rely on the oscilloscope's additional power supply or control module; through the supporting BNC cable can be directly connected to the oscilloscope, easy to operate.
Summary
Among the three technologies of oscilloscope current measurement, the shunt is invasive and affects the circuit performance. The current transformer is only suitable for AC signals and is complicated to operate. However, the ETA56053A current probe has become the most convenient and widely adaptable choice due to its separate magnetic core design, AC/DC full frequency band measurement capability and high range and high bandwidth characteristics. Its automatic adaptation function with the oscilloscope, rich optimization skills, and universal design can meet all kinds of measurement requirements from small current to large current, from low frequency to high frequency, and the oscilloscope can directly read in current units, greatly reducing the operating threshold, and is the preferred tool in current measurement scenarios.