Understanding Smart Sensors - Nomads.usp

194 Understanding Smart SensorsTransmittersingle-transistorblocking oscillatorSequentialmultiplexerswitchCapacitortemperaturesensorInertial-drivenpower supplyTelemetry linkLoop antennaDisplayandrecordFrequency totemperatureconverterReceiverFigure 8.12 Piston temperature telemetry system.Temperature-dependent frequencies are generated between 250 kHz and500 kHz for the data channels.Ambulatory monitoring of critically ill patients or patients requiringreal-time diagnostics for analysis purposes has increased the use of medicaltelemetry. This telemetry can be short range within a hospital floor, or longrange for an entire wing. Most telemetry is within the 174–216 MHz (VHF)frequency band for ultra-low power transmission. Higher power requirementsuse an alternative UHF band (450–470 MHz) and require licensing.Real-time monitoring of noninvasive blood pressure, partial pressure ofoxygen, and peripheral pulse provide additional diagnostic and assessmentinformation on many cardiac and respiratory patients. Electrocardiograms(ECGs) and the partial pressure of oxygen can be monitored by two cigarettepack-sizedunits weighing a total of only 380g [30]. A central station receivesthe data, analyzes the data for anomalies, and routes waveform data andparameter data to additional analysis or recording equipment. Consolidatingseveral patients into one remote station can lower hospital costs by reducing thestaff for intensive care and postoperative units, as well as provide an improvedlevel of patient care. More data can be accumulated and analyzed with less