• Switzer Instrument Limited

Pressure Transmitters

Switzer Instrument Ltd offers a new series of Electronic Pressure Transmitters incorporating the latest thin film technology combined with high stability electronics. They are rugged in design and offer an economical alternative to conventional transmitters. Gauge pressure of liquids, gases, vapours and fluids of most corrosive nature can be measured to provide linear 4-20 mA output signal. Process industries generally require different types of hardware for measurement, transmission, indication and alarm generation. These new transmitters have an option to provide indication and alarm function besides transmission in any combination or all features in a single instrument. They also provide features available with any other design such as a very high direct line accuracy, high turndown ratio capability, full temperature compensation, low mechanical drift with ambient and process temperature changes - all achieved through highly stable electronic circuit design. The transmitters also incorporate excellent RFI immunity as well as protection against accidental voltage reversal. The accuracy Is overall ?0.2% of adjusted span throughout its turndown capability. The primary pressure sensing element for the detection is a silicon wafer on which ion implanted piezo-resistive elements are configured in a bridge form. The bridge elements are laser trimmed to unity ratio of corresponding arms. The sensing wafer is suitably protected by SS315 or Monel or Hastelloy diaphragms. When the diaphragm is subjected to pressure, the stress on silicon wafer produces a strain fleying the bridge to give an electrical output which is sensed by an excitation DC source of constant current. The sensor is temperature compensated to ensure minimal drift with ambient and process temperature changes. The mV output signal of the sensor is suitably conditioned by the electronics using the latest integrated circuits. Output is 4-20 mA proportional to pressure. The minimum voltage compliance is 12 V. The highly stable electronics facilitate excellent external load characteristics at different supply voltages. Pressure ranges are available from a lowest value of 10 m bar to as high as 1000 bar. Transmitters are available in a variety of enclosures made of cast SS or aluminium which are weather and flame-proof for use in hazardous industrial environments. Intrinsically safe versions and transmitters with materials of construction conforming to NACE MR-01-75 for sour gas service are the additional optional features. The transmitter can be installed directly on the pressure line due to its compact size.