Pressure transmitters, also known as pressure transducers, are instruments that convert pressure from liquids, vapors, and gasses into analog electrical signals. These transducers are found in countless devices — including accelerometers, finger-touch key switches, and computer graphic input tablets — designed for a variety of industries, such as factory automation, food processing, skid mount building, and many more.
Pressure transmitters typically come in three types with varying voltage, depending on the application: millivolt, amplified voltage, and 4-20 mA. The transmitter converts electricity when the strain gauges of the diaphragm deform due to a pressure deflection. The strain gauges yield an electrical output directly proportional to the amount of pressure that was input into the transmitter.
An important characteristic of high quality pressure transmitters is overload capacity. Capacitive sensors have a near-zero temperature coefficient, can be optically transparent, and detect flow, motion, and acceleration within a device. Some engineers believe that this technology is sensitive to humidity, noise, instability, and nonlinearity, but with specialized design knowledge we can sidestep these concerns.
How They Work
Like the strain gauges in a pressure transmitter, capacitive sensors are strain-based. Standard sensors are parameter modulated in a half-bridge, push-pull configuration with a conductive spring member in the center. When pressure acts upon a sensor’s isolated spring member, the capacitance of one side of the push-pull symmetry configuration increases while the other side’s capacitance decreases.
In pressure transmitters with non-isolated capacitive sensors, the support structures allow the measurand to touch the spring member, causing it to deflect as a result of pressure. Depending on the pressure acting upon the spring member, it will deflect towards or away from the support structures.
Benefits of Capacitive Sensors
Capacitive sensors extend the performance and longevity of a device over time. Advanced models such as overload ceramic capacitance sensors offer resiliency for pressure transmitters to resist corrosion and abrasion, while also enabling superior technical performance and signal transmission.
Some specific capabilities of capacitive sensors include:
- Detecting material compositions
- Precise measurement of microscopic movements as small as 10-14 m
- Ratiometric position measurement to improve stability
- Measuring bandwidth acceleration and linearity
- Increasing device integration through signal processing
Endress+Hauser provides a global network of sales and service representatives for a variety of instrumentation, much of which requires pressure transmitters and capacitive sensors.
For more information, click here to view our product line of pressure switches and transducers.