Reed level sensor: Defining the measuring range flexibly

A float-based level sensor with a reed chain is really a widely used and comparatively economical solution for continuous level measurement in vessels. Users can define its measuring range flexibly within a given range. This article describes what must be taken into account.
With a reed-chain level sensor, the guide tube includes a defined number of reed contacts, with respect to the measuring range. These are combined to form a measuring chain. The contacts react to the magnetic field of the float, which moves within the guide tube good liquid level.
Accuracy depends on the distance between the contacts
The accuracy of this energy-free level monitoring depends, subsequently, on the distance between your individual contacts: the smaller it is, the more accurate the measurement. เพรสเชอร์เกจ in WIKA?s RLT series, for instance, enables measuring ranges with contact distances between 3 and 24 mm. However, a reed chain cannot be stretched along the entire amount of the guide tube. It is because you can find ?dead bands? at both ends of the tube, i.e. sections that the float will not detect because of design constraints (see graphic).
The graph shows how the maximum possible measuring range (M) having an air-handling series level sensor is defined: Guide tube length (L) minus dead band (T) and 100 % mark (X).
Maximum measuring range isn’t a must
The measuring range of a level sensor therefore lies between the two dead bands specified in the data sheet. Within this range, it could be freely defined. However, it is by no means essential to utilise the maximum possible measuring range in all applications. pressure gauge octa of the amount of contacts to the measuring task also has an economic advantage: The reed chain is one of the most expensive components in a level sensor.
Example ? pressure gauge 10 bar run monitoring
For dry run monitoring in an oil tank of a compressor, for instance, only the lower portion of the guide tube is needed for the measurement. In cases like this, top of the measuring point of the application form (100 % mark) is set correspondingly low. It marks the distance to the sealing face of the process connection. The measuring range is thus defined by the next equation:
Measuring range length M = guide tube length L ? dead band T ? 100 % mark X
Consequently, the measuring range for detecting a maximum level is set starting from the sealing face. In cases like this, the guide tube could be adapted to along the measuring range.
Note
Further information on the RLT series level sensors can be found on the WIKA website. Assuming you have any questions, your contact will gladly assist you to.
Also read our articles
Level sensors ? the agony of choice
What do dead bands mean with a float switch?
There are also out more about float-based level measurement utilizing a reed chain in the following video:

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