Frequency Response Analyser

The Frequency Response Analyser (FRA) control panel lets you stimulate and measure the frequency response of two port networks such as power supplies, filters, audio power amplifiers, power planes, transformers, servo amplifiers and physical systems. You can use it to measure the impedance, phase, capacitance, inductance, Resr and Quality Factor/Dissipation factor of components or networks. We also include power supply specific functions to measure live power supply performance. You can measure the Gain/Phase (with automatic sig gen amplitude control), Input Impedance, Output Impedance, and PSRR vs frequency. 

Take the Impedance Measurement Tour to get an introduction to using the FRA system.  

The CS701 isolated signal generator is especially useful for stimulating live non-ground referenced feedback loops. It has low capacitance to chassis ground(16pF) , and generates from DC to 65 MHz. You can increase versatility by using the CS1070 power amplifier. It has 50 MHz bandwidth, 1 A output, -20V to +30V output swing and can be used for PSRR, Input and Output impedance measurement, as well as offsetting capacitor DC bias up to 30V. 

If you are designing or verifying feedback systems such as power supplies, audio power amplifiers, servo amplifiers and physical positioning systems it is very helpful to measure the Gain/Phase response of the feedback loop. You can use the Phase Margin as a measure of stability. Values of 50-60 degrees represent the optimal response to a step change in load or signal, without oscillation or sluggishness. The FRA uses the CS701 isolated Sine Wave Generator to stimulate the feedback loop at the output of the power supply or amplifier - just where a load would be applied. You don't need an injection transformer as more traditional approaches use, which means you get operation from DC to 65 MHz, no distortion from the transformer, and lower cost. Using a CS328A-FRA you can plot and visualize stability and transient response on a live system. Note that the FRA capability is built into all our capture products. You will however get best performance when using the isolated CS701 signal generator.


The 300 V RMS isolated CS701 can be used on mains powered systems safely, while the +/- 24V DC offset capability of the input to the CS328A-FRA means you can measure the response down to DC in power supplies of up to +/-24V. For higher voltage power supplies, use AC coupling.

The FRA Control Panel makes is easy to set up everything in one place - you don't need to know how to use the rest of the Cleverscope system. Using the FRA control panel you can fully evaluate a transformers transfer response, the primary and secondary inductances, the leakage inductance and interwinding capacitance versus frequency. Using DC offset you can check saturation and DC sensitivity. You don't need to buy an expensive Network Analyser because the Cleverscope FRA does all this for you over a 0-65Mhz frequency range!


Click on FRA Manual to download the FRA chapter out of the Cleverscope Manual

Why not check out our Cleverscope FRA white paper on Power supply response. Also check out these videos:

Measuring low impedance ceramic capacitors

We use the Cleverscope FRA system and hand made jig to measure the impedance/frequency curve for a low impedance 22uF ceramic capacitor. We examine it's application in power supply filtering.

Measuring a composite capacitive impedance

Following on from the measurement of the 22uF capacitor, we add a Wurth 330uF polymer electrolytic capacitor in parallel, and look at the resulting Impedance and Resr.

How to save FRA data points to text file

Use the Cleverscope Frequency Response Analyser to measure and then save FRA data points to a text file for analysis with an external program such as Excel or Matlab. We also show how you can use the AddRef to see a family of captured curves.

Power Supply Rejection Ratio

Use the Cleverscope Frequency Response Analyser to measure the Power Supply Rejection Ratio (PSRR) of a power supply with the CS1070 Power Amplifier.

Filter Response

Use the Cleverscope Frequency Response Analyser to measure the Gain/Phase response of a Minicircuits BBP-30+ bandpass filter.

Input Impedance

Use the Cleverscope Frequency Response Analyser to measure the input impedance of a power supply with the CS1070 Power Amplifier.

PSU Gain/Phase

Use the Cleverscope Frequency Response Analyser to measure the Gain/Phase of a power supply. This video shows you how to connect up a CS328A-FRA to measure the Gain/Phase of an LTC3589 over the frequency range 20 Hz - 1 MHz.

BNC Fixture Calibration

The FRA BNC Fixture calibration procedure corrects for amplitude, gain and phase errors introduced by a test fixture.

Family of Curves

You can use the 'AddRef' persistence command to make a family of curves, and then step around them, and make further measurements as needed.

Output Impedance

Use the Cleverscope Frequency Response Analyser to measure low impedances (1mOhm - 20 Ohm) including on live Power Supplies.
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