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Understanding operating temperature limit specifications for pressure transducers14th October 2007 If the process pressure you are measuring has a dynamic temperature range, determining whether a pressure transducer is going to tolerate the temperatures it will be subjected to will ensure a longer service life and prevent premature failure. There are two main temperature ranges that should be considered before commencing a search for a pressure sensor. First is the variation in media temperature where you will need to determine the likely minimum and maximum temperature of the process. How often the temperature extremes are reached will have a bearing on the life and accuracy of the pressure transducer. A pressure transducer that experiences frequent temperature extremes puts more stress on the fabricated components which for many pressure transducers include industrial adhesives, brazed welds, glass to metal seals and O ring seals. If the temperature extremes are infrequent it may not be necessary to ensure accuracy to maximum or minimum temperature since they are not typical process temperatures and therefore the pressure transducer accuracy is unlikely to be that critical at the temperature extremes. When specifying pressure transducers you will normally find a media operating temperature range and a compensated temperature range somewhere in the technical data sheet. To ensure reliability the temperature extremes of the process should not exceed the manufacturer's quoted operating temperature for the pressure transducer. Excessive high temperatures can affect materials used in the construction, causing them to crack or melt or more subtlety a temporary or permanent change in the pressure transducer's performance. Very low temperatures can also cause cracking due to thermal stressing and any oil fillings used to isolate a sensing diaphragm behind an isolation membrane will wax at low temperatures affecting the dynamic response of the pressure sensor. The process temperature limits for which it is important to ensure pressure measurement accuracy should be within the compensated temperature range, since this defines the limits over which the temperature errors are verified by the manufacturer. The second temperature range to consider is the ambient temperature range. For many pressure transducers the sensing technology will withstand a higher temperature than the signal conditioning electronics which are more isolated from the media in the back of the pressure transducer housing. Some manufacturers will quote a separate temperature range for the media and the ambient environment so that it is possible to use the pressure transducer with process media temperatures that are outside the limits of the ambient temperature range of the pressure transducers conditioning electronics. If the ambient temperature range is exceeded the vulnerable components could be active micro-electronic components which become unstable at high temperatures. The solder used to mount the electronic components might melt causing short circuits or an integral cable used to terminate the electrical connection could be compromised if the recommended ambient temperature limits are exceeded. Related Products Temperature measurement instrumentation High media temperature pressure transducers Combined temperature and pressure measuring instrumentation Associated Articles Accuracy factors for pressure transducers |
Site Last Updated: 03/09/10
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