LEYBELOD 850-400-G1 Multi-channel vacuum gauge controller

This guide provides the technical breakdown of the Leybold / Inficon 850-400-G1. also known as the PG3 Vacuum Gauge Controller.

This device is a legacy industry standard for measuring and controlling vacuum levels in industrial and laboratory settings.

1.  Product Description

The 850-400-G1 (PG3) is a multi-channel vacuum gauge controller originally developed under the Leybold-Heraeus/Inficon brand.

It is designed to interface with Pirani vacuum gauges (thermal conductivity sensors).

The unit serves as a central hub that provides power to the sensors, processes their analog signals, and displays the pressure readings on an analog or digital scale (depending on the specific faceplate configuration).

It is highly regarded for its reliability in "rough" to "medium" vacuum ranges.

2.  Technical Parameters

Model: 850-400-G1 (PG3 Series)

Measurement Range: Typically $1 times 10^{-3}$ mbar to $1000$ mbar (depending on the Pirani sensor used).

Input Channels: Supports dual (2) Pirani gauge inputs.

Power Supply: 110V / 120V AC (Standard version).

Output Signal: Analog output for data logging or PLC integration.

Control Interface: Often equipped with adjustable set-points (switching relays) for process control.

Display: Multi-scale indicator for precise pressure monitoring.

3.  Product Advantages & Features

Modular Design: Features plug-in modules (such as Pirani input cards) that allow for easy maintenance or replacement.

Dual Channel Monitoring: Allows the operator to monitor pressure at two different points in a vacuum system simultaneously.

Robust Analog Circuitry: Known for stability in environments with high electromagnetic interference (EMI).

Set-Point Relays: Integrated switching contacts allow the controller to automatically trigger valves or pumps when specific pressure levels are reached.

Ease of Use: Simple calibration potentiometers on the front panel for "Zero" and "Atmosphere" adjustments.

4.  Application Cases

Load Lock Systems: Monitoring the pressure in entry chambers for semiconductor processing.

Vacuum Packaging: Controlling the vacuum levels in food or industrial sealing machines.

Coating Systems: Used as a safety interlock controller to ensure high-vacuum pumps (like turbopumps) only start after the backing pressure is low enough.

Freeze Drying: Monitoring the sublimation process in pharmaceutical or food laboratories.

5.  Related & Other Models

The 850 series includes various controllers optimized for different sensor technologies:

850-610-G2: A Cold Cathode (Penning) vacuum gauge controller for higher vacuum ranges ($10^{-2}$ to $10^{-9}$ mbar).

PG3 Digital: The modernized version of the 850-400-G1 featuring a digital LED/LCD readout.

Inficon VGC Series (VGC012 / VGC401): The modern successors to the legacy PG3 line, offering touchscreen interfaces and fieldbus communication (Profinet/EtherCAT).

Compatible Sensors: Primarily used with TRIVAC pump systems and Thermovac (TM20/TM21) Pirani gauges