These MKS HPS series 421 cold cathode ionization gauge controllers 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 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.

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 log 10 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. On the rear of the control unit are a 9 pin D-sub, SHV, and SMA connectors. The D-sub connector is for the pressure output signal and process relays, while the SHV and SMA connect the high voltage and ion current signal to the tube, respectively.

See the available download section below for the MKS HPS 421 users and operations manual in pdf format.