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Mission 37 · Pro Analogue instruments exercise

Catch a broken wire

Spot a failed transmitter and stop trusting its number.

If LT-101’s wire breaks, its signal fails. Turn SignalFault ON while LevelRaw is below –691 (3.6 mA or less) or 29376 or more (21 mA or more). While SignalFault is ON, keep LevelPV at its last good value and stop the fill pump. PumpOn runs only while Fill is ON, LevelPV is below 80% and SignalFault is OFF.

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The 3D process tank this mission runs on Pro mission
Test replay

Good readings scale and fill

Test 1 of 5
Set by the testChecked by the testStep 4 of 4 · 240 ms
Level
Applied
Time
About 20 min
Reward
+300 XP
Rig
3D process tank
Siemens editors
SCL, LAD, FBD
Rockwell editors
Structured Text, Ladder, FBD
Course stage
22. Don’t trust a dead signal
Automatic tests

What the tests check

  1. SignalFault comes ON at both ends: below –691 counts, and at 29376 counts or more.
  2. While the signal has failed, LevelPV holds its last good value and PumpOn is OFF.
  3. When the signal comes back, SignalFault clears and LevelPV follows the tank again.
  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

A forklift catches a transmitter cable on a tank skid. The screen still shows the last level while the tank keeps filling.

A frozen number looks real. The programme must spot the failed signal, flag it and stop anything it controls before the tank overflows.

Where you'd find thisMaking one batch of drink

At a drinks factory, valves let measured amounts of water and syrup into a mixing tank. An electric mixer blends them into one batch. An outlet valve then sends the drink to a holding tank. Filling machines bottle it from there.

  1. Ingredient tanksHold the water and syrup
  2. Mixing tankFill, mix and measure one batchYou are here
  3. Holding tankKeeps the finished drink ready
  4. Bottle fillerPuts the drink into bottles
On a real site: places, parts and safety
  • Drinks factory — blending water and syrup
  • Paint factory — mixing ingredients into a consistent colour
  • Water-treatment works — preparing a measured chemical mixture
  • Brewery — heating water for washing equipment

A full tank does not close its own inlet. Water keeps arriving until the valve closes, so an open inlet can flood the room.

A heater that is not covered by liquid can overheat. Real tanks have separate safety devices as well as the PLC programme.

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

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