1.To measure the closest distance of 72cm using laser ranging, the timing circui

Question

1.To measure the closest distance of 72cm using laser ranging, the timing circuit should be able to resolve ____ time difference.

Select one:

a. 120 ns

b. 240 ns

c. 2.4 ns

d. 1.2 ns

2. For ultrasonic method of level measurement, consider two cases-

(i) The transmitter(Tx) and receiver(Rx) are mounted at the bottom of the tank, submerged in the liquid,

(ii) Tx and Rx are mounted at the top of the tank outside the liquid

then the time taken by the sound wave to travel from Tx to Rx and the liquid level are ____ proportional for case (i) and ____ proportional for case (ii) respectively.

Select one:

a. directly, directly

b. inversely, inversely

c. directly, inversely

d. inversely, directly

3. A stepper motor has 100 per step and must rotate at 250 rps. What input pulse rate, in pulses per second, is required?

Select one:

a. 150 pulses/s

b. 9000 pulses/s

c. 9000 pulses/min

d. 150 pulses/min

Explanation / Answer

1) Answer : C :2.4 ns

Laser is a light with velocity = 3*108 m/s

measuring distance = 72 cm = 0.72 m

Time difference = measuring distance / velocity of laser = 0.72 / 3*108 = 0.24*10-8 second = 2.4 ns     .......1

2) Answer : a : directly,directly

It doesn't matter where Tx and RX are kept at bottom or top of the tank as soundwaves from the Tx need to travel through liquid and are reflected at the boundary and then again reflected waves travel through liquid and are received by RX. Hence time taken is directly proportional to level in oth cases.

3) None of the given options.

Stepper motor has 100 steps and it must rotate at 250 rps.

for one revolution pulses required are 100 as motor has 100 steps.

Therefore to rotate at 250 rps stepper motor should have 250*100 = 25000 pulses/ second

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.