The Keysight / Agilent / HP 8903A Audio Analyzer combines the capabilities of several instruments under microprocessor control to yield accurate and rapid characterizations of audio signals in the range of 20 Hz to 100 kHz. It contains an audio source, measures distortion, SINAD, signal-to-noise ratio, ac and dc level, and counts frequency completely auto-remote control. This combination reduces the number of instruments and complexity of setup needed in many applications.

The analyzer is ideally suited for performing audio measurements on transceivers. Along with a suitable signal generator and modulation analyzer, receiver sensitivity and transmitter distortion measurements can be made accurately and rapidly.

With the internal source and measurement functions enhanced by microprocessor control, the 8903A has more measurement capability and less display ambiguity than separate instruments. The Audio Analyzer makes true rms measurements for ac level and distortion, thus assuring more accurate measurements of complex waveforms and noise. The ability to perform swept measurements makes it an extremely versatile stand-alone bench instrument for general audio stimulus/responses work. Its programmability over HP-IB is well suited to system applications.

The Audio Analyzer performs several measurements and contains various features specifically designed for receiver testing. The most common audio measurements are SINAD for FM receivers and signal-to-noise for AM receivers. In the 8903A, these measurements are optimized for measuring the noisy signals encountered in the receiver testing. Measurements of SINAD are indicated both by the analog meter and the digital display. The specifically marked meter for EIA and CEPT sensitivity and selectivity results in fast, accurate, repeatable measurements. Also, a psophometric filter allows testing to CEPT standards.

By combining the 8903A with the 8901A Modulation Analyzer, you can make all common transmitter tests. The 8903A provides the tone for microphone inputs, measures transmitter audio distortion, and counts squelch tones. Distortion measurements can be made using the 400 Hz high pass filter to reject squelch tones. In rapid frequency count mode, counter measurements can be made at a rate of 8 ms/reading, allowing burst counting of squelch tone frequencies. In rapid source mode, the 8903A can switch frequencies rapidly enough to generate multiple squelch sequences. All functions are remotely programmable.

The 8903A simplifies general audio testing by combining several traditional audio instruments into one. It is fully automatic and autoranging, so most measurements take only a single keystroke. Microprocessor control of all functions greatly enhances measurement flexibility. For example, distortion can be displayed in either percent or dB. In ac level you can choose between volts, dBV, or watts by entering the load resistance from the keyboard. You can establish a reference and make measurements in percent or dB relative to a measured or entered value. Using the source increment/decrement keys and relative display mode it is easy to determine parameters such as the 3 dB points of filters and amplifiers. With both low-distortion source and analyzer built in, the 8903A makes stimulus-response measurements. Internal processor control over all functions expands this capability to powerful swept characterization. With only a few keystrokes you can measure frequency response and swept distortion characteristics of filters, high quality amplifiers, audio IC's, and other devices. Hard copy results are easily generated with an X-Y recorder connected to the analyzer's rear panel outputs.

The Audio Analyzer is a powerful HP-IB system component. Many low frequency functions frequently required in automatic systems are combined in the 8903A. In many cases it does the work of an audio synthesizer, digital voltmeter, frequency counter, and custom interface with notch filters. All measurements are available at a single input connector. As a result, interfacing requirements, hardware cost, and software development time are reduced. The 8903A makes a major contribution by automatically measuring distortion under HP-IB control. It also provides a low distortion programmable source. Typical combined distortion of both source and analyzer at 1V is <0.003% between 20 Hz and 20 kHz.

Often systems applications involve measuring low level ac signals. The 8903A's most sensitive range features a full scale ac level display of .300 mV with an accuracy of 4% of reading (2% of reading > 50 mV, 20 Hz to 20 kHz). The ac converter is true rms for correct noise measurements and the 3 dB bandwidth is greater than 500 kHz.

Large measurement systems often have troublesome noise problems. The 8903A has 30 kHz and 80 kHz low-pass filters to reject high frequency noise. Also, the 400 Hz high-pass filter rejects line related hum and noise more than 68 dB. Floating the input or output can break insidious ground loops, and provide up to 60 dB of common mode rejection.

Two special binary programming modes are available in remote operation. Rapid frequency count mode provides a packed four byte output for fast counting. Also, the rapid source mode allows the internal source to be programmed directly with five bytes.