Separate interface from measurand
The phrase 4–20 mA describes a signal range. To interpret it, identify the measured variable, units, scaling and sensor geometry. A local probe near one nozzle sees its immediate surroundings. Wiring that signal to an analog input does not give the probe visibility of the whole tank.
A simple counterexample
Imagine a sensing tip installed 0.30 m above the bottom of a 2 m tank. With the same liquid fully covering the tip, the tank could contain a surface at 0.50 m or 1.80 m. Unless the specified sensing principle measures that change in surface position, a local covered response cannot distinguish those two heights. Scaling the PLC display from zero to 100 percent would therefore create an unsupported level indication.
A numerical sensor response can still be useful. It can help observe differences between validated local process states or reveal changes that deserve investigation. This usefulness is separate from continuous level measurement.
Check what the actual PL20 version provides
Baumer lists a digital push-pull output and a 4–20 mA output for the specific PL20S-11534.133013.G07020020000 product page. That is evidence for that variant, not a promise about every PL20 or legacy LBFS. Obtain its current manual to establish the assigned analog variable, configuration, pinout and fault behavior.
Choose the correct instrument for inventory
If the requirement is changing surface height, volume or inventory, evaluate a continuous-level measurement system and the vessel geometry. If the requirement is a high or low permissive, evaluate a point switch. Both may be useful in one installation, but their signals should be named accurately in the PLC and operator display.
What to confirm for your application
- Measured variable, units and scaling
- Exact variant and supported operating mode
- Pinout and analog-input compatibility
- Fault indication and displayed engineering units
- Whether inventory or only local presence is required
References
Baumer — PL20S-11534.133013.G07020020000, product-specific technical data
Endress+Hauser — Basics of continuous level measurement
Technical guidance. Verify the current order-code documentation and your plant requirements before applying a recommendation.