How Weston Aerospace Vibrating Cylinder Pressure Sensors Work
The Weston Aerospace vibrating cylinder air pressure transducer is designed to measure absolute air pressure using the vibrating element principle, providing a frequency output from which pressure is computed.

The pressure is applied to a thin-walled metal cylinder, which is set into motion at its natural frequency by electromagnetic drivers. As the air pressure inside the cylinder changes, the resonant frequency of the cylinder also changes. This frequency is detected by electromagnetic pick up coils which feed it back to the drive circuitry so as to maintain the resonant state. The ‘new’ resonant frequency can then be equated to the absolute pressure.

During manufacture the transducer is calibrated by measuring the resonant frequency (time period), and diode voltage (temperature) across a matrix of 77 data points (11 pressures, 7 temperatures), covering the full working pressure and temperature ranges.

A ‘curve fit’ equation is then used to produce a pressure calculation algorithm. Each and every transducer has a uniquely defined set of constants used in an equation of the following general form:

Where:

P = Calculated pressure
S = Scaling factor for chosen system of pressure units
K = Unique transducer calibration constants
X = Modified diode voltage variable
Y = Modified frequency (time period) variable

The pressure calculation may be performed in real time by the customer’s processor or alternatively a look up table can be generated using the above equation for storage in non-volatile memory.

A Digital Pressure Module is now available, which houses the transducer in an enclosure together with conditioning electronics and a microprocessor, that computes the pressure computation and configures the output in RS232 or RS485 data format.