Selecting the Right T&M Equipment for Medical Electronics

An overview of essential test parameters and technological improvements in test and measurement of medical devices

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Proper maintenance of medical electronic devices is critically important. Medical equipment are expected to comply with many predefined standards, which require active T&M involvement to ensure accurate readings for remedy or diagnosis. All medical instruments—be it an ECG machine, an ultrasound machine or even a pacemaker—have their specific set of test devices. These devices are constantly improving by incorporating better technologies.

Optimal functioning of medical electronic devices depends on the environment, electrical capacity and operational processes. To know whether an equipment is being handled effectively, environmental parameters such as humidity, temperature, sound level, voltage, current and pH need to be measured. That is where basic T&M devices like thermometers, pH meters, voltmeters, ammeters and humid sensors come into play.

To improve user experience, test equipment are becoming smaller in size, shedding their bulky and space-consuming form factor. There are many more important upgrades in T&M equipment for medical devices, some of which are given below.

Signal testing

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Electromedical hardware design is following the path of miniaturisation. Medical devices are increasingly using electronic chips with micro-actuators and micro-sensors. T&M has evolved accordingly by incorporating more test probes and going digital. Signal analysers and digital oscilloscopes are being modified with features fit for medical electronics.
Real-time functioning of medical devices is different from other electronic instruments.

General-purpose devices can be tested by injecting known signals as test cases and verifying the output on an average to assure proper functioning in real life. But medical devices may need to monitor signals that vary every millisecond (like a person’s heartbeat). Keeping this in mind, one of the most important features of medical T&M devices is their ability to measure single-shot signals.

A single-shot feature is essential to differentiate signal-to-noise ratio and get accurate readings. This ensures that the medical equipment being used is capturing correct signals under critical setups. Test setups for medical devices like ECG and EEG machines greatly benefit from these features.

T&M manufacturers are making their instruments more modular and compact. Amitesh Kumar, senior business development specialist, Liquid Instruments, cites an example: “One of the innovations in our test setup is an arbitrary waveform generator, which allows users to enter any equation including waveforms that can be analogous to the complex signal models generated by the human body in different test profiles. You need not have a computer with a catalogue full of different waveforms. This greatly speeds up report generation.”

Electromagnetic compliance

Electromagnetic compliance (EMC) plays a crucial role in electromedical design and test. Electromagnetic interference (EMI) can disturb device readings or even render the device dysfunctional. Thus EMC testers are in great demand for electromedical testing.

Sumit Sharma, marketing manager, Good Will Instrument Co., mentions, “Earlier, T&M manufacturers used to provide only spectrum analysers for EMC testing. Now, the trend is to offer a package of pre-compliance EMI testing and EMC evaluation together. It includes all the necessary accessories and probes to analyse whether the device is compliant to set EMC regulations, and, if there is any abnormality, to identify the source of abnormality.”

Anritsu’s MS2830A signal analyser
Anritsu’s MS2830A signal analyser

Madhukar Tripathi, sales manager, Anritsu India, cites an example from their T&M roster: “Anritsu offers EMI test setups using spectrum analyser MS2712E or MS2830A for medical electronics devices. MS2830A signal analyser comes with an EMI pre-compliance test feature.”

Wireless chip testing

With wireless connectivity trending in medical devices, T&M equipments are required to evaluate connectivity modules on chips. Separate equipment are available for Wi-Fi modules, Bluetooth chips and GSM chips.

Test sets capable of analysing Bluetooth modules of medical devices are in demand. Tripathi mentions, “We have upgraded our Bluetooth test set to provide better evaluation.

The device supports T&M for basic rate, enhanced data rate and Bluetooth Low Energy (BLE) measurements. It analyses transmission power, frequency, modulation and receiver sensitivity. The equipment has improved to the level where a single button can initiate a measurement script. Also, these can test a medical device in less than 10 seconds.”

Current flow and pressure testing

Insulation is an important safety aspect in medical electronics. Thus it becomes an essential test parameter. A spokesperson from Tektronix mentions, “Measuring leakage current of medical electronics devices is very important since these devices are often in contact with the human body. So, leakage current testers are greatly utilised by medical instrument testers.”

Saumil S. Patel of Spectrum Medtech adds, “Measuring the pressure of medical devices is very important for optimal maintenance. We use specific pressure-measuring instruments. Device pressure can be evaluated in two parts: low pressure and high pressure. For medical devices used in angiography and angioplasty, the low pressure should be around 450 pounds per square inch (psi) and the high-pressure reading should stay within 1200psi.”

The ProSim 8 ECG device tester from Fluke
The ProSim 8 ECG device tester from Fluke
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