Scale the tank level

The brief

Client

Ashcombe Water

Site

Storage tank T-301

Work order

AW-2609

Industry

Water treatment

Task code

PLC-09

Difficulty

Intermediate

Type of work

Programming

Turn raw analog counts into a level, pick the pump set points from a recipe, run the fill pump between them, raise high and low alarms that do not chatter, and treat a broken transmitter cable as a fault.

What you do

1. Read the client brief and the tag table: 11 tags, 4 inputs and 4 outputs.
2. Write the logic in ladder, Structured Text or SFC.
3. Press Simulate and watch the plant answer your program.
4. Run the factory acceptance test and fix what fails.

Skills you practise

• Analog scaling (integer maths)
• Compare and MOVE
• Level control with hysteresis
• Alarms with a dead band
• Signal fault (live zero) handling

What the test checks

The factory acceptance test runs 7 numbered tests against your program. The numbers in the brief are drawn per learner. The tests are:

• Scaling: 4 to 20 mA becomes 0 to 1000
• Clamping: Level stays between 0 and 1000
• Recipes move the right set points
• Pump runs between the start and stop levels
• High alarm with a dead band
• Low alarm with a dead band
• A broken wire is a fault, not an empty tank

In this lab

• Ladder, Structured Text and SFC in one studio
• A plant that answers: motors, tanks, conveyors
• Numbered tests mark your program