Isolated oscilloscope designed to measure high voltage

14th July 2017

Alice Matthews

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Datasheet

An isolated high common-mode rejection ratio (CMRR) four-channel 200MHz 14-bit oscilloscope has been introduced by Saelig, the Cleverscope CS448. It has been designed to measure high voltage, fast slew-rate signals such as those in a full or three-phase power electronic switching bridge (e.g. gate drives to measure voltage and charge, power switching to measure loss and parasitic stress, output signals to measure power and spectrum for EMC compliance, control system signals for gain/phase and stability).

The CS448 includes a built-in isolated 65MHz signal generator to provide stimulus signals, and eight isolated 100Mb/s logic inputs to measure digital control signals. The CS448 has 110dB frequency domain dynamic range using its 14-bit ADC's, which is suitable for EMI and frequency response analysis. Two CS448's can be slaved to make an eight channel oscilloscope with coherent sampling.

The CS448 has been designed from the ground up to accurately measure small voltages while exposed to large (less than 1,000V) swings. While the input ranges available are ±0.8 and ±8.0V, attenuating probes are used to extend the input range up to 800V. The application software automatically scales the values to adjust for probe attenuation. Sampling at 500MSa/s, all four channels are phase aligned with better than ±140ps skew so the CS448 can be used for impedance and gain/phase measurement.

The CS448 provides coherent measurements of the channel inputs and the built-in tracking generator. The signal generator has greater than 110dB CMRR at 50MHz, with a working isolation between the output and ground of 800VRMS. 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.

The CS448's free application software allows a USB or Ethernet connected Windows PC to provide operating controls and display. A built-in Link Port is used for controlling Cleverscope accessory devices such as the CS1070 1A 50MHz power amplifier, or the CS1110 VCE Sat Probe. The CS448 also includes RS232, SPI and I2C ports for the control of other user equipment.

With optically-isolated channels, a high dynamic range and an internal signal generator, this combination in the CS448 is targeted for measuring power switching values, carrying out tradeoff analysis, and verifying the design and operation of power electronics designs. Designed and made in New Zealand by Cleverscope, a test equipment manufacturer, to be compact in size (9.75x6.5x2.2") and weight (5.5lb), the CS448 is available now.