Английский язык для судовых электромехаников (Кущ, Воловник) - страница 36

The primary aims of control are to reduce the inefficiencies inevitably associated with human machine minding. A complete elimination of human judgement is quite impracticable. However highly developed an automatic system may become the skill and experience of the trained operator will still be essential.

20 20

Home exercise. Choose a suitable title for the story and give reasons for your choice. Be prepared to dwell on the subject expanding the examples from the story.

Now I feel I must tell you how Thomas Alva Edison (1847—1931) made one of his greatest discoveries. It happened like this.

One summer evening in 1879 a glow worm sat on a pear which Mr, Edison was about to eat. This incident set him thinking for a time. T|hen he exclaimed joyfully: “Of course! Now I know!”, and . . . the electric bulb was invented.. .

Hometask: Ex. 10, 15, 20.

The third class period

21 3

Listen to the\ sentences and define in each of them the meaning of the word “set”.

1. Clear input permits to reset counter at any time. 2. Data inputs and load input are for presetting counter to desirable initial number before counting of clock pulses. 3. The table shows the technical data of standard electrical equipment sets. 4. The level of the voltage is set by the voltage adjusting potentiometer.

Listen to two recorded texts about wattmeters. Which of these texts contain the most interesting information for electricians? Compare the description of these two wattmeters.

A

A wattmeter is used to measure the value of power. It is connected to the circuit directly. A wattmeter consists of coils: two fixed coils and a coil which moves in the magnetics field produced by the fixed coils.. Wire used for the coils must have a high resistance. The fixed coils are in series with the load, the moving coil is connected across the line in series with a resistance. When a wattmeter is used, the reading on its scale shows the value of power being used.

В

The text from ex. 23, Section I, Unit 2, Figure 4 will help you.

Fig. 4. Operation of the wattmeter

23 6

Fulfil or explain the following:

1. Name inputs of synchronous counters.

2. Name outputs of synchronous counters.

3. Explain the sequence of operations of the counters.

4. Diagram the construction and principle of operation of the counters.

24 5

Record your answers on a tape.

1. What should be done before counting of clock pulses?

2. What feature allows the counters to be used as module-N dividers?

3. How would you know that you have the direction of counting correctly determined?