A float-based level sensor with a reed chain is a widely used and comparatively economical solution for continuous level measurement in vessels. Users can define its measuring range flexibly within a given range. ไดอะแฟรม ซีล describes what needs to be taken into account.
With a reed-chain level sensor, the guide tube contains 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 the energy-free level monitoring depends, in turn, on the distance between the individual contacts: small it is, the more accurate the measurement. pressure gauge octa in WIKA?s RLT series, for example, enables measuring ranges with contact distances between 3 and 24 mm. However, a reed chain can’t be stretched across the entire length of the guide tube. This is due to 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 is not a must
The measuring selection of an even sensor therefore lies between your two dead bands specified in the info sheet. Within this range, it might be freely defined. However, it is by no means necessary to utilise the utmost possible measuring range in all applications. The exact adaptation of the number of contacts to the measuring task also has an economic advantage: The reed chain is one of the most expensive components in an even sensor.
Example ? Dry 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 this instance, top of the measuring point of the application (100 % mark) is defined correspondingly low. It marks the length to the sealing face of the procedure connection. The measuring range is thus defined by the following 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 determined beginning with the sealing face. In this case, the guide tube can be adapted to along the measuring range.
Note
More info on the RLT series level sensors are available 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?
You can also find out more about float-based level measurement utilizing a reed chain in the following video: