Knowledge BaseHOME/SERVICE & SUPPORT/KNOWLEDGE BASE

Audio.TST September 2007 Automation in the 2700 Series

Created 02 Sep 2007

Notes from the Test Bench

By Bruce Hofer, Chairman & Co-Founder, Audio Precision

Hello addressee_placeholder

September was a heavy travel month for Audio Precision. Two weeks ago we were at IBC in Amsterdam; at the same time, we sent an engineering team over to Japan, South Korea, and Singapore for customer visits, all of which were very productive.

IBC has grown considerably during the past 10 years and now rivals the US NAB show in size and significance. Audio Precision was very happy with both the number and quality of people who stopped by our exhibit to see our products. Our APx family of analyzers drew particular attention as broadcasters searched for multichannel solutions to test inbound and outbound signals and amplifier manufacturers continued their search for faster production test.

Following the show, I spent several more days visiting some of our good friends and customers in the Netherlands before returning to the US.

Next up is the Oct 5-8 AES Convention in New York , where we will debut the latest version of the APx measurement software. I look forward to seeing you there.

Bruce.

Output: Tech tips and new applications from AP

Automation in audio test Audio Precision is conducting research on automation in audio test & measurement. We'd really appreciate your input. This is your opportunity to influence design of future products.

Send your answers to audio.tst@ap.com or click for an online version of the survey:
First 100 respondents get a free AP hat.

Free AP hat to the first 100 respondents .

1. What Audio Precision instruments do you use?

2. How many Audio Precision instruments does your company use?

3. What is the primary task for which you are automating your instrument?

(Cut and paste answers from below as necessary)

Manufacturing test and quality assurance
Design verification
Logo certification (I.E. Dolby, DTS, Microsoft Vista, etc…)
Automation of routine tasks
Other:___________________

4. Which automation system/environment do you primarily use? (Cut and paste answers from below as necessary)

AP Basic (with or without using the macro recorder)
APx500 Measurement Navigator
Microsoft Visual Basic
Microsoft C++ or C#
National Instruments Labview
Other:____________________

5. Do you integrate the AP instrument with other instruments and systems?

6. If you had the choice, what would be your preferred method for controlling an AP instrument in your automation application?

Sound Advice: Audio Test Q&A

AP Applications Engineer Eric Schultheis reviews the basics of Regulation with a 2700 Series audio analyzer.

Using the Regulation feature in your 2700 Series instrument

Regulation is a software servo-mechanism which enables you to automatically steer test parameters toward a specific measured value. Let's say, for example, that you would like to find the point at which a power amplifier produces 1% THD+N at its output. With regulation, the 2700 Series instrument can adjust a generator output amplitude while monitoring the DUT THD+N, guiding the generator up and down to the level where 1% THD+N is measured. At this point, the DUT output wattage can be measured and noted as the power level at 1% THD+N.

Here's another example: you'd like to find the exact frequency (by using the Regulation panel Source properties) at which the DUT response is 3 dB down from the midband level reference (selected in the Regulation panes Target properties . ) The regulation function can adjust a generator frequency while monitoring the DUT output amplitude, guiding the generator up and down to the precise frequency at which –3 dB is measured.

Using regulation not only saves your time and keystrokes, it can facilitate full and/or partial automation of tasks otherwise requiring human monitoring and input.

The Regulation panel enables you to select:

a Target parameter
a target Value
a target value Tolerance
a Source parameter
source High and Low Bounds

The Target is the parameter AP2700 is monitoring as it is steered toward the target Value. Use the target browser to select the target parameter from the AP2700 instrument readings provided.

The Regulation target Value is the reading from the DUT that you are trying to attain by varying the Source.

The Regulation Tolerance is the range around the target Value that is acceptable for your test.

The Regulation Source is the AP2700 setting which will be varied in an attempt to steer the Target parameter toward the desired Value. Use the Source browser to select the source parameter from the instrument settings provided.

The High and Low Bounds are the extremes between which you want to confine the Source variations.

There are also several panel settings which affect regulation performance:

Operation sets one of five algorithms which determine how the regulation operation proceeds:

Linear The assumption for Linear operation is that any change in the Regulation Source parameter will cause the same change in the regulated Target parameter. This the normal relationship, for example, in the input and output amplitudes of an amplifier: a +2 dB change at the input should make a +2 dB change at the output. Linear is the best choice and the fastest option for setting DUT outputs to a reference level, or making frequency response measurements at a constant output level. In Linear operation, the regulation algorithm is directed to jump to the Target value in a single step, and the Stepsize field is unavailable.
+ Normal The assumption for + Normal is that any change in the Regulation Source parameter will cause a proportional change in the regulated Target parameter. This the normal relationship between generator amplitude and measured THD of an amplifier near its maximum power point, or between generator frequency and measured high-pass filter output amplitude on the attenuation skirt.
– Normal The assumption for - Normal is that any change in the Regulation Source parameter will cause an inverse proportional change in the regulated Target parameter. This the normal relationship between generator frequency and measured low-pass filter output amplitude on the attenuation skirt, or between generator amplitude and measured THD+N in relative units (dB or %) in the lower, noise-limited range of a DUT.
Maximum Maximum regulates in search of a maximum or peak value, steering the Source parameter to find the peak.
Minimum Minimum regulates in search of a minimum peak value, steering the Source parameter to find the minimum peak.

The Stepsize field controls the initial size of the increments which will be made to the regulation Source parameter. When the regulated parameter reading first passes beyond the Target value, the actual step size will be decreased and the direction of change reversed as the algorithm goes into a binary search mode to determine the final value to regulate the measurement. Stepsize may be set in a number of ratio units including %, X/Y, and dB. The optimum value for Stepsize depends upon the DUT and the distance to the Target value from the initial starting value. Large steps will reach and pass the Target rapidly, but more iterations will be required to reduce the step size and bring the measurement into regulation. Smaller steps will take longer to reach the approximate area near the Target value but may regulate the measurement more rapidly.

Iterations determines the maximum number of regulation steps which will be made for each measurement. Regulation is considered successful if the target Value is attained within Tolerance without exceeding Iterations. If Regulation is unsuccessful an "Unregulated" message issued, and an "R" is entered at the measurement on the Graph, in the Data Editor and in the Log file, if enabled. For + Normal , - Normal and Linear operations, the Iterations field limits the maximum number of steps which the regulation algorithm will make in the search for the Target value. Iterations should be large enough to permit successful regulation. In Maximum and Minimum modes, the Iterations field determines the number of times that the measured value passes through the target value before the algorithm halts. A larger Iterations value will produce a more precise location of the target, but will take longer to complete. Generally, broad peaks and dips can be located with a smaller Iterations value, and sharper peaks or dips require a larger Iterations value.

The instrument readings used for regulation are first processed through the sweep Settling algorithm. In some circumstances, depending upon the variability of the readings and the Settling settings, Settling cannot be satisfied and no data for that step will be forwarded to the Regulation panel. The Timeout field enables you to enter a time interval beyond which regulation will not wait for a settled reading. When a reading times out, the most recent stream of up to 32 readings from the instrument will be averaged and used as input to regulation.

Once you have made all your settings, click the Regulate button to perform regulation.

Check Regulate at each sweep step to set the automatic option for sweep operation.

Test Results: AP News & Events

Competition: Test Bench of the Year Please visit ap.com/news/test_bench.htm to view the winners' benches. Several runner ups are also posted. And the winner is...

Overall winner Noe Rubio, Televisa San Angel, Mexico Noe has a great setup with numerous pieces of AP gear, and a great pose.
Best Equipped Bench Noe Rubio, Televisa San Angel, Mexico
Most cables Etienne Lémery, Ing ENSEA, France
Proudest owner / biggest grin on an engineer Brian Curtis, DTS, USA