Practice missions
Practise in
0 XP
Practice missions
Mission 71 · Pro PLC programming exercise

Read it at a glance

Answer 'is it all right?' in one second, in plain words.

Turn the air handler's cluttered overview into one an operator understands in a second: its status in words where the eye lands first, values with their normal band, and nothing they don't need. Then write the status number the screen turns into words.

This mission is part of ProTry the full course, every mission and the expert challenges free for 7 days. No card needed.
The 3D air handling unit this mission runs on Pro mission
Test replay

Starting, then running on target

Test 1 of 3
Set by the testChecked by the testStep 6 of 6 · 420 ms
Level
Applied
Time
About 25 min
Reward
+300 XP
Rig
3D air handling unit
Siemens editors
Ladder (LAD), SCL
Rockwell editors
Ladder, Structured Text
Beckhoff editors
Structured Text
Course stage
37. Operator screens 2: read it at a glance
Automatic tests

What the tests check

  1. The top-left corner shows the unit's status in plain words.
  2. The supply temperature shows on a bar with its normal band, to one decimal place.
  3. The overview shows only the values that say whether all is well.
  4. UnitStatus is 4 on FrostAlarm and 5 on FanFail; frost wins if both are on.
  5. UnitStatus is 0 off, 1 while State is 10 or 20, and 2 while running on target.
  6. UnitStatus is 3 only after 30 s in State 30 with SupplyTemp more than 2.0 °C from .
  1. Try it Use the buttons below the model and watch the rig respond.
  2. Test solution Every check runs on your code in one press.
  3. Replay If one fails, step through it one scan at a time to see why.
Why it matters

Where you’d see this on site

One person watches every air handler in a building from one screen, with about a minute to spare for each.

If the overview needs studying, a frost trip waits until people complain about the cold, and by then the coil may have split.

Where you'd find thisFresh air at 21 °C, without freezing the coil

Every office, hospital and factory has air handling units on the roof or in a plant room. The controller starts them in a safe order, proves the fan is really moving air, and holds the supply temperature with a PI loop.

  1. DamperOpens first
  2. FilterCleans the air
  3. CoilPI heatingYou are here
  4. FanProven by airflow
On a real site: places, parts and safety
  • Offices, schools and hospitals
  • Factories and warehouses
  • Clean rooms and laboratories

Fan starts are interlocked to the damper: a fan against a closed damper can collapse ductwork.

Frost protection overrides everything: stop the fan, close the damper, open the valve.

The sizes, timings and cutaways are teaching choices, not a drawing of any one real installation.

Keep going

Next in the course