Case Studies

Visual and Audible Alarm Synchronization Tester

Posted in Infrastructure, LabVIEW, Test & Measurement Automation


DMC designed and implemented a system for performing automated testing of visual (strobe) and audible (alarm) signal appliances to ensure that these devices comply with UL and ANSI standards.

The strobe light testing involved monitoring strobe flashes over an extended period of time to verify that the flashes of multiple strobe appliances remain synchronized within a certain timing tolerance.  The audible alarm testing involved monitoring the sound output from multiple appliances to verify that the signals of multiple devices remain synchronized and that they match a specified temporal pulse pattern.


The test control software application was developed using the National Instruments LabVIEW development platform.  A single application supports both visual (strobe) and audible alarm synchronization testing.  These two different types of tests are available to configure and execute completely independently of each other.  Thus, the test station is capable of performing a strobe flash synchronization test by itself, an audible alarm synchronization test by itself, or both types of tests at the same time.

The front panel of the test station enclosure provides BNC connector jacks for all relevant data acquisition channels for easy connection / disconnection of probes/sensors.

The primary interface provides the operator with the ability to select which tests they wish to run, start and stop those tests, and configure the pass/fail grading parameters that should be applied to evaluate the performance of the device under test (DUT).

After each strobe light or audible alarm synchronization test is completed, the test system evaluates the data acquired during the test and evaluates it according to the test grading specifications for that device.  Various test setup parameters (like test duration, etc.) and grading parameters (such as max and min pulse widths/periods, etc.) can be adjusted by the user through a password protected “Engineering Parameters” interface.  This allows flexibility to perform stricter or more lenient tests of devices to accommodate changing test specifications.

After the data acquired during a test has been analyzed and graded according to the specified parameters, the final results of the most recent test are displayed on the monitor of the test station and are logged to a summary report file.  This file is given a descriptive name to link it to the time the test was performed and the serial number (or other unique identifier) of the device that was tested.   The report file is generated in a PDF format to allow for easy subsequent printing of these results. 

The Visual and Audible Alarm Synchronization Tester also supports the ability to verify its measurement of input signals against a known, calibrated, trusted reference instrument in order to validate the measurement capabilities of the test system.

Customer Benefits

  • Automation: Executing tests (of any duration) is fully automated, requiring a single "Start Button" press to begin the testing process
  • Flexibility: Engineering Parameters interface allows authorized users to change grading pass/fail criteria to accommodate varying performance specifications
  • Accuracy: High performance data acquisition hardware capable of capturing analog input samples at 250 kS/s with 16-bit resolution
  • Dual Functionality: Single test station can perform visual (strobe) or audible synchronization tests independently of each other, and simultaneously if desired
  • Cost Effectiveness: Utilizing single PC and single DAQ card to enable testing of two different device types reduces net hardware costs for each test station
  • Results Accessibility: Auto-generated PDF reports make results easy to view across platforms or print as a proof of performance certificate