HPS 421 MKS Instruments Cold Cathode Ionization High Vacuum Gauge Controller

The MKS Instruments HPS SensaVac Series 421 Cold Cathode Ionization Vacuum Gauge System is part of MKS/HPS SensaVac family of vacuum gauge for industrial and research use. The MKS Instruments HPS SensaVac vacuum gauges cover pressure range from atmosphere to 10^-11 Torr. The MKS Instruments HPS SensaVac Series 421 Cold Cathode Ionization Vacuum Gauge System features digital and anlog Pirani gauges, thermocouple gauge, hot and cold cathode ionization gauges, and the unique MODUCELL Pressure Sensor/Vacuum Switch. Features in some of the units are simple to use controls with front panel access, exclusive leak detection mode with audio and bar graph, liquid crystal, LED and analog meter displays, user selectable units of measure, adjustable process control set points, analog outputs and operation on all common line voltages and frequencies. The SensaVac gauge tubes are rugged and may be mounted in any position. They are interchangeable without calibration.

The MKS Instruments HPS SensaVac Series 421 Cold Cathode Ionization gGauge controller is microprocessor based for versatility and added functions. Color coding relates switch position to the functions of the two push button switches making most of the operations of the controller self-evident.

The liquid crystal display (LCD) makes possible the presentation of more information than a typical luminescent display. It is visible in a wide range of lighting situations and over a wide viewing angle. Depending upon the function selected, it shows pressure in exponential notation, the units of measure in use, a 30 segment zero center bar graph for leak detection, status of the two set points and diagnostic information. the display is updated four times per second when the controller is operated on 60 Hz power.

Two independently adjustable set points are standard . The set points are m=nonvolatile and remain unchanged after turn-off or power failure. Te controller are set within their operating range by turning the rotary switch to the desired set point, 1 or 2, which displays the pressure value at which the respective set point is activated. The UP and DOWN push buttons are used to adjust this value. this provides an unambiguous and repeatable method of adjusting set points.

The controller provides an analog output signal accessible at a rear panel connector. The 0 to 8 volt (1 volt per decade) signal is proportional to the Log₁₀ pressure. To enable a computer to distinguish between vacuum with zero output, and the case where the analog output is zero because the power is off or the unit is defective, a one volt offset can be selected if desired, using DIP switch inside the controller. This makes the analog output at and below 1x 10^-10 Torr equal to one.

Every time the unit is turned on or switched to TEST, it performs a sequence of tests to verify correct operation. Certain malfunctions and controller faults are shown by an error code. The correct operation of all elements of the display is also tested.