The Hg tube on the plate is used for recording the Franck–Hertz curve. It is a replaceable high-vacuum tube filled with mercury, which evaporates when the tube is heated in a heating oven.
| Heater | 0–7 V, max. 150 mA |
| Grid voltage | 0–60 V |
| Retarding voltage | 0–3 V |
| Tube dimensions (mm) | l = 130, d = 28 |
All units adapted for 110V/60Hz. Contact us for volume pricing and grant assistance.