Notes from the Test Bench
By Bruce Hofer, Chairman & Co-Founder, Audio Precision
Well, it’s been another summer month, and we have been having some unusually hot weather here in the Pacific Northwest. Indeed, Portland almost tied its all-time record high of 107°F by hitting 106°F on two consecutive days. Fortunately, this is not the norm around here. Even in this unusually high heat, we were pleased to see that our Calibration Lab maintained its tight regulation of operating temperature with hardly any fluctuation.
The final touches have been put on the latest APx500 v2.4 software release, and it is now shipping along with the new AG52 generator option for the APx520 Series. Special kudos to our software team for a job well done. Now, we look ahead to future enhancements and even more new features.
Later this month I am off to the Danish Technical University (DTU) in Copenhagen, Denmark to help with Professor Andersen's extremely popular course on class-D amplifier design. This year, we have been asked to conduct a more hands-on measurement lab for the students’ amplifiers. So, we have been busy taking care of the logistics of getting five of our APx525 systems, cables, test loads, and AUX-0025 filters ready for shipment. I am really looking forward to this event.
Well, that's about it this time from the bench. Keep your soldering tips clean, and watch out when using the X-Acto knife.
Output: Tech Tips and New Applications from AP
APx in Production Test: Automation Without Programming
Unique to our APx Series is the ability to automate production line testing without writing any code. In this month’s audio.TST, we look at the current features of the APx500 software that make this possible.
The heart of APx automation is the Sequencer—it lists, in order, all the audio tests that will run when a sequence is started. You can add and delete tests, modify tests, and drag and drop them to change the order. Before and after each test, you can also add user prompts to give instructions, collect information, run an external program, or display a pass/fail message. In addition to running tests, the Sequencer can also automatically set generator and analyzer reference levels. Optional password protected locking prevents changes to the settings.
Limits are essential in rapid automated production testing. There are a number of ways to set limits in the APx software. One way is to measure a known good product sample, and then add a plus or minus offset to create a window of acceptability. You can also import limits from an Excel spreadsheet. The easiest method though is to just draw the limits on the graph with a mouse. However you begin, you can use any of these methods later to manipulate the limits as desired.
External controls, switches, indicators, and logic connected to the rear panel Aux Control Input and Output ports (GPIO) can be integrated into a sequence in multiple ways. For example, an operator might push a footswitch to start an APx sequence running, and then on completion a light-bar might display a green “Pass” or red “Fail”, depending on the outcome. Aux Control can be configured in the user prompt editor, the Aux Control Out step editor, and in the Sequence Properties.
Accurate reporting is necessary for quality control, defect auditing, rework instructions, and more. APx500 software can automatically save a report in various formats at the end of each sequence, using filenames automatically set or input by the user (by entered serial number, for example).The automation features in the APx500 software are continually being expanded, and in most cases provide everything you need to automate your testing. However, if you want full control over nearly everything the APx Series analyzers can do, there is a complete API to integrate APx into any .NET capable programming language, such as VB.NET, C# or LabVIEW.
Sound Advice: AP Knowledge Base
AP2700 and ATS-2 ActiveX Automation Commands for Programming with LabVIEW or Other Languages
All of Audio Precision's instruments are highly suited to automation, including AP's 2700 Series and ATS-2, which can be programmed using their extensive built-in AP Basic language. For additional flexibility and integration, both instruments can also be controlled using LabVIEW and other languages. This month's knowlege base article by Director of Technical Support Joe Begin gives tips for finding the right ActiveX commands to use in these situations.
When writing AP2700 and ATS applications with the AP Basic macro editor, you can quickly locate automation commands with the built-in Microsoft IntelliSense auto-complete typing feature. But if you are programming in LabVIEW or other languages, where do you find the ActiveX automation commands needed to control a SYS-2700 or ATS-2 audio analyzer? Here are a couple of tips:
Basic Extensions Help
The 2700 or ATS Basic Extensions Help, located under the Help menu, has detailed information on virtually every ActiveX automation command available. That’s because AP Basic itself uses ActiveX automation to control the 2700 or ATS-2 audio analyzer, and the AP Basic commands are very well organized and documented in the help system. The listings on the right side of the help dialog are hyperlinks to detailed information about each command.
Using Learn Mode
Learn Mode is a great feature available to AP Basic users. While in Learn Mode, your actions and the settings you make are recorded and converted into the corresponding AP Basic commands. But even if you’re using a programming language other than AP Basic, Learn Mode can help you find the ActiveX commands needed to control features of the AP2700 or ATS2 software.
For example, suppose you are using LabVIEW with AP2700 and you want to find the ActiveX commands needed to set the Digital Output to PSIA. To find the commands using Learn Mode, first start recording your actions by clicking the Start Learn Mode button on the toolbar.
While Learn Mode is active, the mouse pointer changes to an icon of a cassette tape. Now, open the Digital I/O panel ...
... and change the Output control to PSIA.
To stop Learn Mode, click the Stop Learn Mode button on the toolbar. Now, look at the code in the Macro Editor panel. As you can see, the system automatically inserted the AP Basic commands corresponding to the actions you took while in Learn Mode.
By looking at the AP Basic commands that were automatically generated, you can easily tell that the ActiveX command to set the digital output to PSIA is <AP.S2CDio.OutConnector = apbPSIA >. The corresponding LabVIEW code is shown below.
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