|
When to use a pressure transducer with a millivolt output
11th July 2007 The mV output is the least processed out of all the different types of pressure transducer output and it is particularly suited to low power consumption and high dynamic response applications. If you have an unlimited power supply you will be free to select any output signal without having to be concerned about power consumption. However if it is a battery powered application where measurements are to be made over a long period of time, power consumption of the output signal is going to be a significant deciding factor. The millivolt output signal tends to have the lowest power consumption especially those with high input impedance. Also millivolt output pressure transducers have very few active components and therefore there is negligible warm up time allowing the sensor to be pulsed at regular intervals to further reduce power consumption. This makes the millivolt output pressure transducer ideal for incorporating into field instruments such as water level data loggers which have to operate in locations which are remote and often without power.
If you are trying to measure dynamic pressures which are changing very quickly you will need a pressure sensor that has an output signal with a frequency response that is ideally an order of magnitude higher in frequency than the process variable being measured. Although many output amplifiers now have frequency responses in the kHz range this may still not be enough for some applications. Millivolt output pressure transducers provide the highest frequency response for any given pressure sensor technology because there is typically no signal conditioning electronics fitted. Therefore the response of a millivolt output signal is only limited by the natural frequency of the sensing diaphragm and not by any other components.
Millivolt output levels vary depending on the core sensing technology or more specifically the gauge factors of the strain gauges that make up the wheatstone bridge circuit which most mV output pressure transducers use to convert the mechanical movement of the diaphragm into an electrical signal. Pressure transducer technologies such as bonded foil or thick film strain gauge have relatively low mV outputs typically 20-30 mV at full scale pressure whereas silicon and thin film strain gauges have typically 100 mV output at full scale pressure. The majority of mV output signals are ratiometric to supply voltage. There will be a limit on the range of supply voltage which can be used so that self heating effects and diminishing signal to noise ratios do not impact on the pressure transducers performance. Due to the low voltage level of millivolt output signals they are not generally the best solution over long distances and therefore are mainly used on test rigs or inside an instrument where the cable lengths are relatively short between the signal conditioner and the pressure transducer.
Pressure Measurement Resource Links Explain an IP rating for ingress protection Explanations for pressure measurement terms Create a pressure sensor specification
Home
> News > |
Site Last Updated: 10/05/08
Tools
Resources
Pressure Measurement Glossary - Find explanations of terminology used for specifying and using pressure instruments
Contact
News
RSS
|
