Potentiometric liquid-level measuring device

BM 500 – Potentiometric liquid-level measuring device
  • Hygienic installation
  • Completely made of stainless steel
  • Maintenance / seal-free installation

The BM 500 level gauge operates on the potentiometric measuring principle and is designed for use in all electrically conductive products with a minimum conductivity of 1 µS/cm (e.g. distilled water).

This method is particularly suitable for measuring levels in small vessels containing viscous, pasty or heavily caking products. The electronic evaluation unit is integrated in the connecting head and supplies a level-proportional output signal of 4 … 20 mA.

The HWM 500 hygienic process welding sleeve ensures installation in conformity with standards of hygiene. Due to its high temperature resistance (140°C / 285°F), the BM 500 is eminently suitable for CIP cleaning and sterilizing processes.


  • Fruit juice
  • Ketchup
  • Beer
  • Toothpaste
  • Dairy products

Measuring principle

The measuring principle is comparable to that of a slider potentiometer, with in this case the liquid representing the slider pick-off.

An alternating current is applied to a stainless steel tube to cause a drop in voltage via the electrical resistance of the tube (cf. slider path). The conductive wall of the vessel forwards the tapped voltage conducted through the liquid to a high-resistance amplifier. Based on the supply voltage, this yields the ratio between the depth of immersion and the total length of the tube. 

Together with the high-resistance pick-off, this ratio explains why the measuring system is independent of the conductivity of the product. Sticky deposits merely form a parallel connection with the anyway very low-resistance tube. What is measured, therefore, is only the actual product between tube and vessel wall.