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These 10 free C-309 questions are organized by exam domain, so you can see how each part of the Programmable Controller Systems 2 (C-309) blueprint is tested. Reveal the answer and explanation under each question.
A valve-positioning test specifies linear reverse action: 20 mA means fully closed and 4 mA means fully open. At a PLC request of 30% open, the measured output is 15.2 mA and independent travel feedback is 30% open. How should this test point be recorded?
Correct answer: D - Pass this point: current and travel agree with the configured reverse action.
A nonisolated differential analog input accepts a 0-10 V difference, but its specification also requires each terminal to remain between −10 V and +10 V relative to analog common. Measurements show AI+ at +13 V and AI− at +9 V, a difference of 4 V. Which assessment correctly applies the input specifications?
Correct answer: B - The connection is outside specification because AI+ exceeds its permitted voltage relative to common.
A 4-20 mA pressure input is intended to represent 0-200 kPa. With the field circuit disconnected, direct injection at the analog input produces these results: 4 mA → raw 0 → PLC 40 kPa; 12 mA → raw 16,000 → PLC 120 kPa; 20 mA → raw 32,000 → PLC 200 kPa. All three raw values match the configured module specification, and the HMI agrees with the PLC. Where does this evidence place the conversion error?
Correct answer: C - The PLC uses the wrong lower endpoint when converting raw data to pressure.
Under an approved test procedure, a technician replaces a two-wire transmitter with a loop calibrator to command test currents through the existing field wiring and passive PLC input. The external 24 V loop supply remains connected. Which calibrator function matches this externally powered connection?
Correct answer: A - SIMULATE mA, regulating loop current while drawing power from the existing supply.
A mixer must start with a speed setpoint of 35% after each STOP-to-RUN transition, but operators may change it afterward. An accepted HMI entry of 60% briefly appears and then returns to 35%. The PLC contains an unconditional assignment of 35% on every scan. A FirstRun flag is true only for the first normal scan after that transition. Which revision satisfies both operating requirements?
Correct answer: B - Condition the 35% assignment with FirstRun so it executes once per transition.
An authorized technician must replace a pneumatic actuator inside a machine’s crush zone. The HMI is on Stop, the software MCR zone is disabled, and the displayed motion commands are zero. Electrical and pneumatic energy isolators are available and lockable. Under OSHA 29 CFR 1910.147, what is still required before entering the hazard area?
Correct answer: D - Apply the equipment-specific lockout procedure, control stored energy, and verify isolation before starting work.
A temperature-setpoint subroutine copies RequestedTemp into a separate WorkingTemp tag, caps WorkingTemp at 80 °C, and returns the result into AcceptedTemp. It makes no other writes to RequestedTemp or AcceptedTemp. Before the call, RequestedTemp is 95 °C and AcceptedTemp is 60 °C. What should the caller see when the subroutine returns?
Correct answer: A - RequestedTemp remains 95 °C; AcceptedTemp becomes 80 °C.
An HMI lamp labeled RUNNING illuminates as soon as an operator presses Start, even when the PLC withholds the motor run command because a permissive is absent. The drive supplies a verified RunningFeedback tag that indicates actual operation. What change would make the lamp report what its label promises?
Correct answer: A - Bind the lamp to the drive’s verified RunningFeedback tag.
A tank high-level alarm activates at 80% or above and clears at 74% or below. It activates at 83%, an operator acknowledges it, and the level then falls to 77%. Screen A shows all active alarms; Screen B shows all unacknowledged alarms, including cleared events. No other filters apply. Where should this event appear now?
Correct answer: C - Screen A only; the event remains active and is acknowledged.
A tank-level display retains its last value of 18% after the input quality changes to BAD. The PLC has inhibited filling because the measurement is invalid, and no independent current level is available. The operator needs a message that explains the inhibition without presenting an old value as a current measurement. Which message is appropriate?
Correct answer: C - “Level signal invalid; last known value 18%. Filling inhibited.”
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