Metal Capacitive Differential Pressure Sensors and Transducers
Targeting the measurement (down to 0.016bar) of low differential pressure with high static pressure (up to 320bar), BCM SENSOR has developed metal capacitive differential pressure sensors (model 115C) and transducers (model 315M).
The 115C sensor is in fact a differential capacitance system, which is composed of two stationary capacitance plates and in between there is a movable diaphragm as the third capacitance plate. These three plates form the so-called differential capacitance system of two capacitors. When two pressures are introduced to two sides of the movable diaphragm, the difference in these two pressures will cause a displacement of the movable diaphragm and, as a result, change the capacitances of the two capacitors at the same time. This change in capacitances depends on the difference between the two pressures: the bigger in the difference between the two pressures, the more changes in the capacitances of the two capacitors. Therefore, model 115C functions as a differential pressure sensor with differential capacitance as its output signal.
The metal parts of the 115C sensor are made from specially developed stainless steel (SS) and its cells are filled with low-temperature-effect oil, which transfers the two pressures from two 316L SS isolating diaphragms to the movable diaphragm.
For different applications, different oil is filled in the 115C sensor. For general purpose, a standard type-A oil is filled while a type-B oil will be filled for oxygen industry and a type-C oil more suitable for tobacco industry.
When the 115C sensor must be contacted with pressure medium of strongly corrosive, its two isolating diaphragms will be made from Tantalum, Hastelloy-C, or Monel on request, instead of 316L SS.
The 315M transducer is an assembly of the 115C sensor and a metal housing via welding technology, in which a temperature sensor (e.g., a thermal diode or a Pt100) is integrated inside the metal housing. This metal housing facilitates 315M to be installed in a pair of flanges (option: which can be equipped with a three-way manifold), to introduce two pressures onto the two isolating diaphragms of the 115C sensor. Therefore, the 315M transducer can measure simultaneously both differential pressure and temperature of pressure medium at same point of industrial process systems. The electrical interface of the 315M transducer can be made according to customer requirements (e.g., a M12 connector).
The typical applications of 115C and 315M are listed below:
- built smart differential pressure transmitters,
- flow measurement systems,
- hydraulic systems,
- process control systems,
- liquid level control systems,
- biomedical instruments,
- OEM equipment.