Mindray VS-800, Service Manual

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Principles of Operation
2-19
2.4.3 TEMP
Body temperature can be taken with two different methods according to the temperature probe
used. One method is direct measurement with which the temperature is measured by thermal
equilibrium. Therefore, thermistor, platinum resistance or mercury can be used in the temperature
probe. Direct temperature measurement is the standard method for measuring body temperature
and it is commonly used for clinical diagnosis. With this method, we can obtain accurate
temperature reading, however, it takes longer time since we need time for reaching thermal
equilibrium. Another temperature measuring method is indirect, which uses thermal radiation of
human body to obtain body temperature. Thus, the probe can be an infrared sensor. Indirect
temperature measurement takes shorter time but the measurement error is greater
Direct temperature measurement can be classified as continuous monitoring and predictive
measurement. Continuous monitoring thermometer continuously monitors body temperature and
displays the temperature reading in real time by applying the temperature probe to the measured
site. Since it takes time for heat conduction between the human body and the thermometer,
continuous monitoring takes relatively longer time to reach the final temperature, normally 3
minutes in oral mode and 5 minutes in axillary mode. In predictive thermometer, a heating device
is connected with the temperature detector. Time for reaching the thermal equilibrium between the
temperature probe and the measured site is shortened with the heating device before temperature
measurement. Additionally, the temperature at which thermal equilibrium is reached is predicted
according to the temperature curve of the probe in given time. Since the final temperature of the
measured site can be obtained without taking time for reaching the thermal equilibrium, measuring
time can be shortened effectively.
The predictive TEMP mode provide both continuous monitoring (in MONITOR mode) and
predictive measurement (in PREDICT mode).