MEMS vacuum transducer created for cost-effective OEM integration

Posifa Technologies has launched its new PVC4000 series MEMS Pirani vacuum transducer. Created for cost-effective OEM integration, the device comprises a surface-mount MEMS Pirani sensor and microcontroller-based measuring electronics — all contained in an ultra-compact PCB assembly that features a connector-terminated wire harness.

The sensor element is based on the company's second-generation MEMS thermal conduction chip, which functions under the principle that the thermal conductivity of gas is proportional to its vacuum pressure. The transducer's microcontroller-based measuring electronics amplify and digitise the sensor's signal, giving output via an I2C interface. The interface also enables users to store calibration data in the microcontroller used by a built-in piecewise linearisation algorithm to give calibrated output.

To compensate for differences in thermal conductivity due to changes in ambient temperature, the device provides a temperature compensation algorithm, which takes its input from a built-in temperature sensor. Also, a pulsed excitation scheme, where the sensor chip is heated for about 100ms and then turned off for one second, stops signal drift due to self-heating and also lessens the power consumption of the transducer.

The transducer is ideal for digital vacuum gauges. For these applications, the device combines low power consumption with very fast response times of <1.2s and a wide effective range from 1millitorr (0.13Pa) to 1atm (760torr, or 101 Pa).