128A MKS Instruments High Temperature Absolute Pressure Transducer

The MKS Instruments 127A / 128A Absolute Pressure Transducers are capacitance manometers designed to provide accurate, reliable, and repeatable pressure measurements in the range from 1000 Torr (1000 mmHg) to less than 0.1 Torr or micron (10-5 mmHg). These transducers utilize the latest balanced bridge signal conditioning technology to provide accuracy and stability previously unavailable in low cost capacitance manometers.

The Type 127 and Type 128 transducers are specifically designed to meet the needs of vacuum process systems, where environmental and process conditions are particularly demanding. Both units expose only Inconel to the process, which permits use with corrosive or dirty gases, and eliminates contamination of the process with gauge materials. Measurements are independent of gas composition; the 127 and 128 transducers measure true total pressure, regardless of the gas species or whether it is a pure gas or a gas mixture. Temperature control of the sensor minimizes the effects of ambient or process temperature variations typically encountered in process line environments. The 127 transducer has the sensor temperature controlled at 45° C; the 128 transducer has the sensor temperature controlled at 100° C.

RFI shielding is standard to prevent interference from RF or noisy electrical environments. Both units comply with the European EMC Directive 89/336/EEC which governs electromagnetic compatibility. The units are protected against damage due to overpressure such as when the unit is venting to atmosphere between process cycles. The overpressure limit is 35 psia, maximum, for all ranges except 0.1 Torr range which is 20 psia, maximum.

Both the 127 and 128 transducers are compatible with the Type PDR-C power supply/readout units and closed-loop pressure/flow control systems such as the MKS Type 250 Pressure/Flow Ratio Controller or the Type 152/252 Exhaust Valve Controller. In addition, the 127 and 128 transducers work with many commercial ±15 VDC power supplies, and standard digital volt meters (DVMs).

The 127 and 128 transducers utilize the same construction and operation procedures. The 127 unit is controlled at 45° C and has a black case. The 128 unit is controlled at 100° C and has a gray case.