EEL 4658 Elements of Industrial Control Test # 1 Spring 2018 Name 1. The trigger

Question

EEL 4658 Elements of Industrial Control Test # 1 Spring 2018 Name 1. The trigger time for an SCR with a capacitor at its gate ranges from a) o deg to 45 deg b) 0 deg to 90 deg c) O deg to 180 deg d) 180 deg to 360 deg 2. The major disadvantage of using a photoelectric sensor using the opposed sensing method is: a) Cannot detect transparent objects b) Not good for small object detection c) Short sensing distance d) All of the above For measuring level from 0 to 4 meters in a tank, it is installed some ultrasound device, consisting of a transmitter and a receiver, and installed at the 4 m level. It was send a testing signal, received 20 msec latter. Take the sound speed in the air as 340 m/sec. The water level in the tank is: 3. a) 0.6 m b) 3.4 m c) 2.3 m d) 1.7 m0 4. Assu ming the values of all resistors connected to a difference op-amp are the same, what is the output voltage when +3 V is applied to the inverting input and +1 V is applied to the noninverting input. a) +1 V b) +2 V c) +4 V d) -2V

Explanation / Answer

Question 1.

Answer:(c)

trigger time for an scr with capacitor at its gate ranges from 0 to 180 degree. during negative cycle .capacitor charges in negative direction. but when capacitor voltage crosses threshold voltage of gate thyristor turns on capacitor discharges.

Question 2 .

Answer:(d)

opposed mode sensors are used for large detecting range and not for small or transparent objects.

Question:3

Answer:(b)

speed = Distance / Time

340 = distance / 20 ms

distance = 6.8

distance = going distance +coming distance =6.8

or 2*S = 6.8

or S = 6.8/2

or S= 3.4 meter

Question :4

Answer: (d)

  output of difference V0 = - R/R(Vinverting - Vnon inverting)

V0 = - (3-1)

V0 = -2 volt

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