Water Reservoir Level Control Laboratory
Industrial Instrumentation, Signal Conditioning, PLC Control, and Process Automation
Water Reservoir Level Control Laboratory
This case study documents a functional water-level control platform developed for vocational PLC and automation education.
The system combines industrial instrumentation, electronic signal conditioning, PLC programming, electromechanical actuation, and a physical water process. It was designed as a modular and replicable laboratory rather than as a single demonstration prototype.
Authentic Engineering Problem
The original design used an industrial 4–20 mA water-level sensor, while the available PLC accepted voltage-based analog inputs. Rather than replacing either component, the laboratory uses an intermediate signal-conditioning stage to preserve the industrial sensor while making its signal compatible with the available control hardware.
The small physical reservoir introduced a second constraint: the usable sensor output initially occupied only approximately 1 V to 1.9 V, wasting much of the PLC analog-input range. The conditioning circuit therefore expands the effective measurement span to approximately 1–10 V, improving usable resolution while maintaining proportionality to water level.
Electrical noise and process dynamics also produced unstable readings and excessive pump cycling. The implemented solution combines hardware filtering with software hysteresis and temporal logic.
Functional System Path
Water Level → 4–20 mA Sensor → Signal Conditioning → PLC Analog Input → Scaling / Decision Logic → Relay Output → DC Pump → Reservoir
This complete path allows students to connect instrumentation theory to an observable physical process.
Educational Role
The project integrates concepts from electronics, electromechanics, and programmable control. Students encounter analog signals only after developing a foundation in PLC safety, I/O wiring, sourcing/sinking, sequential control, timers, counters, and digital sensors.
Laboratory 11 explicitly bridges the transition from digital to analog control and prepares students for the project by organizing the signal path as:
Sensor → PLC Input → Raw Value → Converted Value → Ladder Decision → Output Action