Magnet Stimulus Tool

Industry: Medical Devices


Most implantable medical devices leverage a reed switch for basic communication with the device after implant by utilizing a simple handheld magnet. Sometimes this is for a backup to standard RF communications and sometimes it is for simple patient-initiated interaction.

From the perspective of device verification testing, this presents a unique test case. Unlike most device functionality to be verified, this asynchronous external event can be applied at any point during the device's normal cycle. The device firmware may be in a sleep state or even performing a critical task when the magnet application is detected. In order to build confidence beyond the diligence already put into the product design, automated device verification testing is typically the best approach to confirming the safe and proper functionality of the device.


The NI PXI-5122 high speed digitizer was used to capture a synch pulse from the device under test. Due to NI's advanced signal routing, the PXI-5122 was able to hardware trigger a preconfigured analog waveform from a PXI-6289 multifunction DAQ card. This waveform simply contained one small pulse that was incrementally moved in the waveform with each iteration of the test. The pulse enabled a FET that functioned as a switch between the power supply and the electromagnet in the test fixture. All the while, thanks to the NI driver and hardware utilization of direct memory access, double buffered continuous acquisition occurred on multiple channels using the same PXI-6289 multifunction card. As a result, the software was able to monitor the various signals on the device under test real time, and ensure appropriate responses resulting from the magnet application.


Using the test application created by Optimation, the medical device manufacturer can now confidently verify the behavior of the device with regard to magnet application. Furthermore, new product development efforts or sustaining engineering efforts that iterate the product design can repeat the testing to ensure faults have not been introduced.
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  • Medical Devices

  • Controls Engineering
  • Software Engineering

  • Test Systems

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