R&S Isolated Probe Tackles Switching Challenges of Complex Signal Types

This week, Rohde & Schwarz (R&S) introduced a new isolated probing system to complement its oscilloscope line. R&S designed the RT-ZISO precision-driven isolated probing system to offer highly accurate differential measurements in fast-switching signal environments.

R&S isolated probing system for an oscilloscope. 

The RT-ZISO's applications include power converter switching analysis, double-pulse testing, floating measurements, shunt measurements, inverter design, and motor drive analysis. R&S claims the new isolated probe raises the bar on isolated probe technology with its sensitivity, range, accuracy, and bandwidth for wide bandgap power designs based on GaN or SiC.  

The RT-ZISO Isolated Probing System

The RT-ZISO system features a “power-over-fiber” architecture that ensures galvanic isolation between the device under test (DUT) and the measurement setup. This architecture improves the common-mode rejection ratio and measurement accuracy. R&S' RT-ZPMMCX passive probe complements the RT-ZISO, offering a bandwidth exceeding 700 MHz with input voltages up to ±60-V DC and 30-V RMS. The low capacitive load of under 4 pF ensures signal integrity, maintaining the waveform shape and timing during low-side gate measurements.

With these features, the RT-ZISO offers a bandwidth range of 100 MHz to 1 GHz, upgradable based on needs, and a high CMRR of over 90 dB at 1 GHz. This system also supports differential measurements up to ±3 kV on reference voltages of ±60 kV with a rise time of less than 450 ps. The device boasts a sensitive input range from ±10 mV and can manage a common-mode range of ±60 kV. The system also includes various probe tips to accommodate different measurement requirements, including micro-miniature coaxial (MMCX) connectors, square pins, and isolated passive probers.

What Are Isolated Probing Systems?

Isolated probing systems are essential tools in electronics testing and measurement, particularly for high-voltage applications. They enable engineers to accurately measure electrical signals while maintaining electrical isolation between the probe and the measuring instrument. This isolation is crucial for safety, signal integrity, and accurate data acquisition.

An isolated probing system typically consists of a high-voltage probe, an isolation amplifier, and a measurement instrument such as an oscilloscope. The high-voltage probe connects to the circuit under test and safely attenuates the high-voltage signals to a level suitable for the isolation amplifier. The isolation amplifier then processes these signals while providing electrical isolation from the measurement instrument. This isolation is achieved using techniques such as optical coupling, magnetic coupling, or capacitive coupling, ensuring that high-voltage transients do not reach the sensitive electronics of the measuring device.

The RT-ZISO can limit CM noise in a system. 

In many high-voltage scenarios, signals are not referenced to the ground, requiring differential measurement techniques. Isolated probing systems can accurately measure these differential signals without introducing ground loops or common-mode noise, which are common issues in non-isolated systems.

Isolated probing systems enhance safety by protecting both the operator and the equipment from high-voltage hazards. Without isolation, direct measurement of high-voltage signals can pose serious risks of electric shock and equipment damage. They also improve measurement accuracy by eliminating ground loops and reducing noise interference, leading to cleaner and more precise signal acquisition. Lastly, they can test complex, high-voltage circuits, such as power electronics, motor drives, and power distribution systems, where conventional probing methods would be inadequate.

Accurate Data for Complex Signals

Testing and measurement are essential parts of the development process for any electronic solution. With the RT-ZISO isolated probing system, Rohde & Schwarz hopes to provide system designers with a means of capturing more accurate data for complex signal types, including fast switching and differential signals. 

All images used courtesy of Rohde & Schwarz.