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Machine Design

Differential Pressure Gage

The HPS Series 901 Plus (901P) Loadlock Transducer combines a MicroPirani sensor for absolute pressure with a piezosensor for both differential and absolute pressures, resulting in the functionality of three sensors in a single transducer.

The MicroPirani sensor is made of a 1-mm-sq silicon chip, letting measurements be made in small volumes. The sensor can read pressures down to 10 -5 Torr. The MicroPirani sensor minimizes effects of convection and can be mounted in any position without compromising accuracy. The piezosensor ensures correct atmospheric-pressure measurements under varying barometric conditions. The piezosensor measures from -760 to 760 Torr from atmosphere. In addition, it offers gas-independent absolute pressure measurement from 50 to 1,000 Torr with an error of less than 1%. The 901P includes RS-485 or RS-232 digital communication for real-time adjustments and monitoring. Although fully digital, the 901 Plus provides analog output. The analog output is based on pressure readings of both MicroPirani and piezosensors, so the transducer provides highly accurate direct-pressure measurements throughout the entire pressure range. For process control, the 901P has three independent setpoint relays. Each relay can be assigned to the differential piezomeasurement or the combined MicroPirani/piezomeasurement.

MKS Instruments,
5330 Sterling Dr., Boulder, CO 80301,
(800) 345-1967,

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