Practical Significance of Attenuation Ratio of Oscilloscope Probe

In industrial scenarios such as switching power supply research and development, motor drive debugging, inverter maintenance, and new energy equipment testing, the attenuation ratio is the core parameter of the oscilloscope high-voltage differential probe and AC/DC current probe, which directly determines the measurement accuracy, equipment safety and waveform reliability. In this paper, combined with the ETA5026 high-voltage differential probe, ETA5301M AC and DC current probe measured parameters, a brief analysis of the probe attenuation ratio definition, core value and practical operation points, the full text of the project measured requirements.

 一、What is the probe attenuation ratio

The probe attenuation ratio is the amplitude compression ratio of the measured original electrical signal transmitted to the oscilloscope. The voltage probe is equipped with multiple attenuation gears; the current probe relies on the attenuation ratio to complete the range division.

Take two typical ETA probes as examples:

- ETA5026 high voltage differential probe: equipped with 100X, 1000X double attenuation gear, used to measure floating high voltage signal

- ETA5301M AC/DC current probe: 10A range output 100mV/A(1X equivalent attenuation),100A range output 10mV/A(10X equivalent attenuation), taking into account weak current and large current testing

Important reminder: the probe attenuation parameters of the oscilloscope channel must be consistent with the actual probe position, otherwise the reading and waveform will be completely distorted.

二、Engineering Practical Significance of Attenuation Ratio

1. Broaden the measurement range, adapt to high and low voltage/size current

After the ETA5026 switches the 1000X attenuation gear, the differential test range is increased from 260V to 2600V(DC peak AC), which can directly test the high-voltage bus of the inverter. ETA5301M relying on the attenuation gear switching, it can not only capture the details of small current, but also withstand the maximum 100A peak high current. A set of probes covers multiple working conditions for testing.

2. Hardware protection to avoid the risk of equipment damage

The high attenuation gear matches the CAT Ⅱ/CAT Ⅲ safety gauge withstand voltage standard, which can buffer the surge impact of the circuit, reduce the probability of probe core breakdown and oscilloscope BNC port burning, and is a safety barrier for power electronic testing.。

3. Reduce the load interference of the probe to the circuit under test

The higher the attenuation ratio is, the larger the equivalent input impedance of the probe is, and the smaller the "pulling effect" on the circuit under test is, which reduces the deviation of circuit working conditions caused by the probe access and ensures the original circuit state.。

4. Guarantee the measurement accuracy of the whole gear

ETA series probes have built-in exclusive compensation circuits, which can maintain nominal measurement accuracy under different attenuation gears, while ensuring high-frequency signal response and common-mode interference suppression performance, and will not cause accuracy deterioration due to gear switching.

三、combination of working conditions, attenuation gear selection reference

Common engineering errors:

Only the attenuation position of the probe body shall be switched, and the channel parameters of the oscilloscope shall not be modified synchronously; the probe shall be tested for long-term over-range overload.

The above erroneous operations can easily lead to faults such as probe zeroing error, core saturation, waveform clipping, and multiple deviation of measured values.

四、Summary

Attenuation ratio is not only a simple signal scaling parameter, but also a probe core design that takes into account range, safety, measurement accuracy and impedance matching.

Reasonable matching of ETA probe attenuation gear and oscilloscope channel setting, adaptation of power supply, industrial control, new energy all kinds of power electronic test scenarios, can not only improve the test accuracy, but also extend the service life of probe and oscilloscope instrument, to meet the normal test requirements of industrial equipment.