Automatic Collection of Amplitude Frequency Response (AFR) Data

ZETVIEW SCADA system was used as a base to develop some turnkey solutions such as projects for collecting the amplitude-frequency responses (AFR) data using sinusoidal signal generators with linear frequency modulation (LinFM) (Figure 1) and logarithmic frequency modulation (LogFM) (Figure 2).

Figure 1

Collection of AFR requires a device with digital-to-analog converter (DAC) which generates and inputs a signal to the object under test, as well as a device with an analog-to-digital converter (ADC) to measure output signal from the object. In general, one device can perform both functions, for example, ZET 017-U8, ZET 017-U2 FFT spectrum analyzers.

To launch the collection of AFR, it is required to set collection parameters:

• start frequency of signal generation (in Hz);
• end frequency of signal generation (in Hz, depends on a particular device used);
• signal level (in V, depends on a particular device used);
• rate of AFR collecting (in Hz/s for LinFM and oct/min for LogFM);
• averaging during results processing (0.1 or 1 second);
• type of calculated values (RMS, crest factor value, amplitude).

Figure 2

By changing start and end frequency of signal generation, as well as rate of AFR collecting, you can select required time of measurement which is displayed on the screen.

Since the SCADA projects allow collecting AFR from 8 channels simultaneously, it is recommended to mark the channels to be used for operation with checks and assign the corresponding ADC channels to them.

The project is ready for operation! Press “START” button to launch the program, while you can see the remaining time of the experiment, as well as the current frequency of signal generation from DAC displayed as an oscillogram. The amplitude-frequency response is built in real time, i.e. immediately during the measurements, but not after. Besides, you can see the generator signal on the screen to control the test progress.

Upon completion, the measured values can be saved and viewed both in text and graphic format.

Using the SCADA projects for collecting AFR, it is easy to estimate the amplitude-frequency responses of vibration boards during their certification. Based on the measurement results, the operating frequency range and the resonance frequencies of vibration units can be estimated. This software solution is widely used for calculating electrical parameters of piezoceramic resonators.

Author of the article and developer of the “Collecting AFR” projects: A. Antonov.

See also: programs of “Metrology” section:

• • Collecting AFR in the logarithmic scale (variable value measurement);
  • Collecting AFR in the logarithmic scale (constant value measurement);
  • Collecting AFR in the linear scale (variable value measurement);
  • Collecting AFR in the linear scale (constant value measurement);
  • Collecting AFR in the logarithmic scale (selective measurements);
  • Collecting PFR in the logarithmic scale;
  • Collecting PFR in the linear scale;
  • Collecting nonlinear distortion coefficient in the logarithmic scale.