Detecting liquid levels with conductive Level Rod Probes

Introduction:

Liquid levels in process and stor- age tanks need to be measured and monitored, since unwanted variations in these levels 

(due to evaporation or removal of the pro- cess liquids) must be corrected. In this respect, there are two different general tasks:

• control of the level in order topermit automatic execution of process operations (such as dosing of liquids)

Possible deposits of encrustation between the tips of the probe can be avoided by ensuring that the difference between the 

probe-rod lengths is at least 60 mm.

The levels of non-conductive or poorly conducting liquids, in which level rod-probes cannot be used, can be controlled and 

monitored by our float switches.

The level rod-probes are available in many different versions:

• with two to five rods for detec-tion of one to four different levels

• with or without an integratedtemperature sensor.

A suitable electronic controller applies a low alternating voltage to the probe rods. A current then flows from the electrically 

conductive tips of the rods and through the conduc- tive liquid to the reference electrode, called the ground rod. The electrical 

circuit is closed. If the liquid level drops below the tip of a probe rod, the related electrical circuit is opened. The electronic controller detects the two states “current” and “no current”.

The ground rod must be at least as long as the longest rod. An addi- tional ground rod must be provided for level rod probes coated 

with PTFE-Compound, if the distance between the tips of the minimum and maximum rods is more than 1000 mm.

Anticorrosion Pigments, Inkjet Receptive Coating, Matting Agent