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Keysight Technologies
Multi-Channel Audio Test using the
Keysight U8903A Audio Analyzer
For Instrument Control
PC for
Power
post-analysis
supply
Switch for
Audio analyzer
DUT channels
(2 channels)
expansion
Application Note
Introduction
Test requirements for car radio, CD receivers, and other devices such as GPS and entertainment
systems are growing increasingly stringent. Manufacturers are expected to perform these multi-speaker
and multi-channel tests while increasing throughput--without compromising test quality. This paper
provides a solution for increasing overall production throughput and meeting these multi-channel
testing requirements. Designed for today's automotive audio needs, the solution uses the Keysight
Technologies, Inc. U8903A audio analyzer together with the Keysight 34970A/34972A data acquisition
(DAQ) switch unit and the 34904A 4 x 8 switch matrix plug-in module.
Challenges
The U8903A provides two analyzer channels yet manufacturers are required to measure multiple
channels of various parameters such as voltage, dynamic range, and THD+N. To meet industry's test
requirements and maintain production throughput, this testing can require six to eight channels.
For example, consider the following scenario. The required testing of car speakers typically includes
multiple speakers. Various parameters for the front and rear, and right and left side speakers must be
tested simultaneously. More than two channels are needed to perform such testing and prevent the
creation of a bottleneck in daily production output.
Solution
To expand the number of channels on the U8903A, a switch can be used. This switch changes the
signal from the device under test (DUT) and sends the data to the audio analyzer and then a computer
for post-analysis. The cover graphic shows a typical test configuration to expand the number of
channels being tested simultaneously.
03 | Keysight | Multi-Channel Audio Test using the Keysight U8903A Audio Analyzer - Application Note
Four-channels testing using the U8903A and
Keysight VEE Software
Figure 1 shows this solution's typical test setup for audio testing. In this example, the
DUT is a car's audio playing standard test tones. To expand the number of channels
that can be tested and support simultaneous parameter testing, the 34970A/34972A
DAQ/data logger switch and the 34904A 4 x 8 switch module are connected to the
U8903A using a customized cable to maintain a balanced connection: the U8903A-107
XLR-to-2-BNC connectors. An automated Keysight VEE program is used to capture the
frequency, AC voltage, and THD+N measurement of the test tone.
Figure 1. Typical audio testing setup using Keysight instruments
With this solution, four-channel testing is done using the following procedures:
1. Connect and power up the instruments shown in Figure 1.
2. Load the test tone CD-ROM in the car radio. In this example, two common test tones
are being tested that are usually performed at a manufacturing site: