Isolated high-voltage 4-channel 200-MHz oscilloscope handles SiC MOSFET apps

Improvements to the Cleverscope CS448 — an isolated high common-mode rejection ratio (CMRR) four-channel 200MHz 14-bit oscilloscope — let it measure high voltages – now up to 1,600 V – for fast slew-rate signals such as those in a full or three-phase power electronics switching bridge. Examples of challenging measurement tasks the CS448 can handle easily are: voltage and charge of gate drives, loss and parasitic stress in power switching, power and spectrum of output signals for EMC compliance, control system signals for gain/phase and stability, etc.

The CS448 includes an isolated 65 MHz signal generator to provide stimulus signals for frequency response analysis, and eight isolated 100 Mb/sec logic inputs to simultaneously measure control signals. Two CS448s can be connected to make an eight channel isolated oscilloscope with coherent sampling.

The CS448’s low-noise design enables accurate measurements of small voltages during large (e.g. 1,000 V) swings. With input ranges of ±0.8 V and ±8.0 V, custom attenuation probes extend the measurement range up to 1600V. The application software automatically scales all values to compensate for probe attenuation.

The CS448 offers higher than 100 dB CMRR at 50 MHz and withstands 1 kV working voltage between each channel and ground. The high CMRR and the isolated design allow high-side gate drives to be measured without large unwanted common mode artifacts. Dead time, pulse timing, gate charge characteristics, and parasitics can all be observed.

Sampling at 500MSa/s, all four channels are phase-aligned with better than ±140 psec skew, so the CS448 can be used for impedance and gain/phase measurement. The signal generator also has greater than 110 dB CMRR at 50 MHz, with a working isolation between the output and ground of 800 VRMS. The CS448 provides coherent measurements of the channel inputs with the built-in tracking generator. In addition, the CS448 has a 110 dB frequency domain dynamic range using its 14-bit ADCs, useful for EMI, and frequency response analysis.

Connection to a Windows PC for display and operation with the application software provided is via USB or a galvanically or optically isolated Ethernet connection. A built-in Link Port is used for controlling Cleverscope accessory devices such as the CS1070 1-A 50-MHz power amplifier, or the CS1110 VCE Sat Probe. The CS448 also includes RS232, SPI and I²C ports for controlling user equipment.

Compact in size (9.75×6.5×2.2 in.) and weight (5.5 lb) the CS448 is made in New Zealand by Cleverscope, an innovative test equipment manufacturer, and is available now at $9,600 from Saelig Company, Inc. Fairport NY. 1-888-7SAELIG. For more information please contact Saelig at info@saelig.com or www.saelig.com.