Siemens Level 1 Electrical #2

To measure electrical …

• current, the ammeter must be in series with the current path.

• voltage, you must disconnect a component lead or a wire before you connect the voltmeter.

• resistance, connect the ohmmeter across the component without disconnecting the supply voltage.

• resistance, the ohmmeter must be placed in series with the component.

• none of the above.

As shown below, a through-beam sensor with fiber-optic cable is used to detect parts on a work piece carrier. If no part is present, the sensor sends a high signal to the PLC. Which of the following statements about the operation of the sensor are correct? Two answers are correct.

• Power failure of the light emitter is evaluated as “work piece not present”.

• The presence of the work piece can only be detected if the light beam is visible.

• It is not possible to detect completely transparent work pieces.

• Fiber-optic cable break on the receiver side is evaluated as “work piece not present”.

• A broken fiber-optic cable at the light emitter is evaluated as “work piece present”.

An automotive application involves an inductive sensor that detects the crankshaft position to adjust the fuel control system. The result of a test measurement at the output of the sensor is shown below. The magnitude (Vpp) and rotational speed are …

• ≈ 1.2 V, 1000 r.p.m.

• ≈ 1.2 V, 3000 r.p.m.

• ≈ 12 V, 1200 r.p.m.

• ≈ 1.2 V, 12,000 r.p.m.

• ≈ 12 V, 300 r.p.m.

Which of the following statements about the functionality of the emergency lighting circuit, as shown below, are correct? Two answers are correct.

• In the event of main power failure, the emergency lamp is not lighted.

• The lamp will be connected to the storage battery as long as the relay remains de-energized.

• As long as the main power is available, it energizes the relay coil.

• Since the relay coil is energized, the N.C. contact is open and the emergency lamp is lighted.

• In the event of main power failure, the secondary of the transformer keeps the battery charged through the rectifier.

Which statements about the mode of operation of a reflective light barrier shown below are correct? Two answers are correct.

• If no object is present, the reflector must absorb the light emission.

• The interruption of the light beam by an object causes the output of the sensor to switch.

• Failure of the transmitter is evaluated as “object present”.

• No voltage between BN(1) and BU(3) is evaluated as “no object present”.

• An advantage is that both transparent and reflecting objects can be detected.

If an object were caught in the upward movement of the car window, stalling the motor, what effect would this have on the window control circuit for a car door shown below? Two answers are correct.

• Increase in voltage drop across sensing resistor R

• Decrease in motor current IMotor

• Increase in motor current IMotor

• Decrease in voltage drop across sensing resistor R

• Decrease in Analog Output Signal

By looking at the given measuring results of the electrical circuit shown below, determine the type of failure in the circuit.

• There is a short between A and B.

• There is a short between B and GND.

• There is a open between D and -Vs.

• Between A and B is an open circuit.

• Between A and + of Vs is an open circuit.

In the control system shown below, after PLC output X.0 is “ON” and K4 is energized, the voltage measured across …

• terminal K4-14 and K4-24 should be 0V.

• terminal K4-13 and K4-14 should be 24V.

• terminal K4-23 and K4-24 should be 24V

• terminal K5-14 and K5-24 should be 24V.

• terminal K5-13 and K5-23 should be 0V.

In the mechatronic subsystem shown below, when the forward contactor is activated and Motor M rotates, which of the following statements could be true if the carriage does not move in the forward direction?

• The friction plates in the clutch are loosely set.

• The friction plates in the clutch are tightly set.

• The contacts of reverse contactor K2 are accidentally closed.

• There is no output signal from limit switch 2.

• Limit switch 2 is not properly adjusted.

A lamp circuit is shown below. It is assumed that one of the three bulbs is burned out. Which of the following conclusions are correct? … Two answers are correct.

• The open branch of the circuit does not change the voltage across all parallel branches.

• When an open circuit occurs in a parallel branch, the total current delivered by the source increases.

• When an open circuit occurs in a parallel branch, the total current delivered by the source remains the same.

• When an open circuit occurs in a parallel branch, the total current delivered by the source decreases.

• The open branch of the circuit decreases the voltage across all parallel branches.