USB-väylän suojaerotus sairaalakäyttöön ; Medical Isolation for USB

Price is an important criterion when new medical measurement instruments are purchased. Because of price competition manufacturers wish to use commercial off-the-self (COTS) products as much as possible. Regular office computers are well-suited for displaying and organizing patient measurement information. The most convenient way of connecting measurement devices to a computer would be via Universal Serial Bus (USB) or Ethernet plug, as they can be found from every modern computer. This thesis examines how USB could be used in a safe manner to connect a medial measurement instruments to regular office computer. Electrically operated medical instruments must have double insulation in order to protect the patient and medical personnel. In practice double insulation means that the device could be used safely even in case of 4 kV voltage applied to the mains power side. The easiest way to achieve the desired level of safety is to have electrical isolation with high breakdown voltage. Regular computer power supplies are normally not isolated. Changing the supply would not suffice if the computer is used also for other than medical instrumentation tasks. The isolation may be accidentally bypassed by for example connecting a non-isolated printer to the computer. Normally it is good to have isolation also between separate measurement units. In order to connect a medical instrument safely to a computer via USB there must be isolation either in the device or on the bus. This thesis presents an isolation implementation for the USB-signal within the device. With minor changes the isolation can be implemented also in USB-cable. The prototype isolation works in full-speed USB, which is 12 Mb/s version. Other speeds of the bus are also considered. All the changes needed to support speeds in the range of 1.5 - 480 Mb/s are described. ; Sairaalaympäristöön tarkoitettujen potilasmittalaitteiden hinta on usein merkittävä tekijä uusia laitteita hankittaessa ja voi ratkaista valinnan kahden tasapuolisen laitetoimittajan välillä. ...