Power Electronics
Economical Network Analyzer

Economical Network Analyzer

Saelig Company Inc. has introduced the CleverScope CS328A-FRA  - a Frequency Response Analyzer (Network Analyzer) consisting of a PC-hosted oscilloscope and spectrum analyzer with a built-in 65MHz isolated signal generator and PC based application software.  The data acquisition unit is a two-channel 10-bit sampler operating at 100 MSa/sec on each channel. It can stream data transfer via USB2.0 or 10/100Mbit Ethernet to a PC at up to 1.5MSa/S for up to 200G samples. Gain and offset are automatically set to correspond to the selected amplitude axis view.  Analog triggering of the waveform in view may be adjusted with a resolution of 1% of the display height. The analog trigger may optionally be conditioned with a low pass, high pass or noise filter. Eight digital inputs are also available for sampling at 100 MSa/sec, with the threshold adjustable from 0 to 10 V in 10 mV increments.

The Cleverscope Frequency Response Analyzer (FRA) uses the CS701 isolated Sine Wave Generator to sweep through a frequency range to determine the frequency response of a circuit, a component, or to stimulate the feedback loop at the output of the power supply or amplifier - just where a load would be applied. There is no need for an injection transformer as more traditional approaches use, which means operation from DC to 65 MHz is easy to obtain with no distortion from the transformer.  The CS328A-FRA provides fast plotting and visualizing of the stability and transient response of a powered system. It injects a small swept-frequency signal into the device under test, and displays a synchronous gain/phase plot to check output amplitude and phase margin.   The CS328A-FRA sweeps the signal generator synchronously with signal capture, and then uses narrow band correlation to measure the gain/phase at that frequency without being affected by the surrounding switch mode power supply noise. The isolated CS701 signal generator can be used on 110V-powered systems safely, while the ± 24V DC offset capability of the input to the CS328A-FRA enables measuring responses down to DC in power supplies of up to +/-24V.  For higher voltage power supplies, an AC coupling is recommended.

The CS328A-FRA can also be used to measure the impedance and phase of feedback networks, transformers, PCB power planes, capacitors, resistors and inductors. The FRA Control Panel makes it easy to measure capacitance, inductance, effective series resistance, dissipation factor and the quality factor of components.  Transformers can be evaluated for transfer response, primary and secondary inductances, leakage inductance and interwinding capacitance, throughout a specified frequency range. Using DC offset, it is possible also to check saturation and DC sensitivity. This is much less costly than a Network Analyzer covering the 0-65Mhz frequency range.  Other applications for the CS328A-FRA include verifying feedback systems such as power supplies, audio power amplifiers, servo amplifiers and physical positioning systems to measure the gain/phase response of the feedback loop. Phase Margin can be used as a measure of stability.

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