In the master's thesis, the design and implementation of a multi-functional device for testing the safety of medical devices and systems are presented.
First, we introduced basic concepts and extracts from the IEC 60601 and IEC 62353 standards, which describe the requirements for testing medical devices. Basic concepts and measurement concepts, as well as other information on measured electrical quantities, are presented. A good understanding of relevant standards is crucial for initiating the design of the measuring part of the instrument.
In the second part, the measurement circuits or input adaptation circuits are presented in more detail. They are designed to capture measured quantities - voltage and current. The input adaptation circuit is followed by an appropriately designed amplification stage for digital acquisition and further digital processing of the observed signal.
The most commonly measured quantity in device testing is leakage current. In the presence of the first fault in the tested device, a dangerous voltage may appear on the touchable conductive part. When such a part is touched, a certain current will flow through the human body. To detect the current that would flow through the human body from touch, the so-called standard model of the human body is used. Therefore, when we connect the measurement clips of the instrument to the actual parts of the tested device, the instrument with the designed input section appropriately detects, processes, and displays the leakage current.
In the design of measurement instrument circuits, various development tools are highly beneficial. When designing the relay matrix that connects the measurement clips of the instrument to internal meters and signal sources, it is crucial to have a comprehensive record of all measurement functions depending on the state of the relays or vice versa. A systematic approach not only facilitates easier development but also greatly simplifies the subsequent detection and correction of errors or the modification of existing measurement paths.
In the case of a multi-functional instrument, we deal with several different signals or measurement ranges of these signals. It is necessary to list all signals and required measurement ranges to appropriately determine the input adaptation stage of the signal and the amplification stage between the input adaptation circuit and the analog-to-digital converter.
The complexity of the relay matrix and the multitude of electrical quantities dictated the development of a simple application that can be upgraded, where design procedures for the instrument are clearly collected in one place. Thus, an application in the MS Excel environment was created, allowing the collection of procedures for multiple different instruments.
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