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Knighten D.,Audio Precision
Electronics World | Year: 2010

A five minute guide to chip level audio test is discussed. The 12S, or Inter-IC Sound is a relatively simple serial data protocol which originated with early CD players as the connection between the optical transport and the digital analogue converters inside the device. It is important to monitor the clock and data lines through a buffered output. Match the timing diagram for the part to the actual timing displayed by the oscilloscope. Using phase offset signals one can also verify the absence of distortion crossover. Troubleshooting connection issues can be rapidly expedited by monitoring the digital signals with an oscilloscope. The unmarked side of double row pin headers is often ground but it is not always safe to assume that. Observe static protection measures to prevent failures.

Mathew D.,Audio Precision
Electronics World | Year: 2010

Dave Mathew, Audio Precision (AP), addresses the issue of earthling in testing and measurement setups, including analyzers and device under test (DUT). He suggests some optimal configurations and means of providing additional grounding where required. Best practice suggests that the chassis ground of each device needs to be directly connected to the ground of the test instrument via wires having low impedance to prevent such problems. The most effective grounding arrangement for multiple devices is 'star grounding' where each device in the systems connected to the measurement instrument ground via a separate grounding wire. A combination star or bus grounding configuration can simplify connections, while providing good grounding performance, by keeping serial links very short. Some companies also provide the parts required to create star or combination star or bus connections to several devices, including grounding cables designed to connect test switches to an analyzer.

Mathew D.,Audio Precision
Electronics World | Year: 2010

Some recommendations that need to be followed to write the engineering specifications, is discussed. The characteristics of the device that are important enough to be included in the specification have to be decided appropriately. The specifications of an audio device usually include the results of four core categories of measurements including level, expressed in volts (V), watts (W), or sound pressure level (SPL), frequency response, expressed as a statement or graph, and noise. Stating ranges and conditions is absolutely essential and every level measurement is made at some frequency or range of frequencies. Every frequency measurement is made at some level or range of levels. Simply decoding the units chosen for the specification and comparing them to a similar specification stated in different units is a challenge that need to be addressed. Lastly, the specification has to be expressed graphically when appropriate.

Liberman A.,Audio Precision
EE: Evaluation Engineering | Year: 2010

The testing of FM radio receivers equipped with radio data system (RDS) requires an FM transmitter or exciter, a small transmitter that is used to drive an RF power amplifier to create a more powerful signal. The transmitter takes the monaural or multiplexed stereo signal with or without RDS and modulates an RF frequency within the FM band. The audio quality of the transmitter must be better than the receiver under test or the measurements will reflect the transmitter's limitations and not the receiver's. The RDS signal must be added to the audio signal after the FM multiplex stage for testing. Audio Precision offers an RDS encoder utility for use with APx Series Audio Analyzers. The utility creates sine wave test signals and multiplexes and combines them with RDS messages. All frequency response measurements taken from an FM receiver show a sharp high-end roll-off just before 19 kHz due to the FM multiplex filter.

Begin J.,Audio Precision
Electronics World | Year: 2012

Constant voltage method was used to accurately test impedance using the constant voltage method. Two analyzer inputs were used to make the measurements, channel measures voltage across the sensing resistor and the other measures voltage across the speaker. To make the connections easier, a measurement test jig that contains a 0.1ω 50W current sense resistor was constructed. In addition to offering more convenient connections, the 4-wire Kelvin configuration provides more accurate sensing measurements. The impedance is derived from the level result in the acoustic response measurement. The input channels are re-labeled in signal path set-up. A multiplication by 0.1 is equivalent to an offset of -20dB.

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