This is a cold cathode ionisation Gauge consisting of two electrodes anode and cathode.
This is a cold cathode ionisation Gauge consisting of two electrodes anode and cathode. A potential difference of about 2.2 KV is applied between anode and cathode through current limiting resistors. A magnetic field is introduced at right angles to the plane of the electrodes by a permanent magnet having nearly 800 gauss magnetic field which will increase the ionisation current.
The electrons emitted from the cathode (gauge head body) of the gauge head are deflected by means of magnetic field applied at right angles to the plane of the electrodes and are made to take helical path before reaching the anode loop. Thus following very long path, the chance of collision with gas molecule is high even at low pressures. The secondary electrons produced by ionisation themselves perform similar oscillations and the rate of ionisation increases rapidly. Eventually, the electrons are captured by the anode and equilibrium is reached when the number of electrons produced per second by ionisation is the sum of positive ion current to the cathode and the electron current to the anode and is used to measure the pressure of the gas.
The Cold Cathode Penning gauge is designed on this detection method to read vacuum from 10-2 to 10-6 m.bar. The vacuum reading efficiency is enhanced by utilizing cross coupled static magnetic and electron fields of the gauge head. The gauge is stabilized to high voltage DC power supply of about 2 KV. The ionization current in terms of vacuum can be noted from the front panel micro-ammeter. All the high voltage points in the penning gauge are well insulated to eliminate any accidental contact by the user.