## Measuring devices

### I.Read and learn the following words.

Of the same type or design – одного й того ж типу або дизайну
identical moving units may be used for either meter – однакові рухомі частини можуть використовуватись для будь-якого з цих вимірювальних приладів
positive or negative lead – позитивний або негативний підводжувальний провідник
in series – послідовно
is the product of – є витвором
direct reading – безпосереднє значення
otherwise the readings will be incorrect – у протилежному випадку показання були б невірними
is to be measured – повинна вимірюватись
as high as possible – як можна вище
a drop in potential – падіння потенціалу
across the circuit – в данних точках ланцюгу
by means of – за допомогою
the instantaneous values – миттєві значення
in this instance – у цьому випадку
consumed by it – їм потрбляемим
due to - через
at any instant – у будь який момент

### II. Read and translate the text.

Ammeters and Volt meters. - Ammeters measure the current flowing in a circuit and normally have scales which are graduated or calibrated in amperes, milliamperes or microamperes.

Voltmeters are used to measure the potential difference between two points in a circuit. The calibration of voltmeters is usually in volts, millivolts or microvolts.

The main difference between the two instruments of the same type or design is in the resistance of the operating coil, identical moving units may be used for either meter. An ammeter is connected in the positive or negative lead in series with a circuit and, therefore, must have a low resistance coil, otherwise the readings will be incorrect as the coil would absorb an appreciable amount of power.

A voltmeter is connected in parallel across the points of a circuit where the difference of potential is to be measured. The resistance of the operating coil must, in this instance, be as high as possible, to limit the amount of current consumed by it, or else a drop in potential due to the meter would occur and the pointer indication would not represent the true potential difference across the circuit.

Wattmeters - The measurement of the power in a D. С circuit at any instant can be achieved by means of an ammeter and voltmeter as the power in watts is the product of the current and the voltage. With A.C. circuits, however, the instantaneous values are always changing. To measure A.C. power correctly, therefore, it is necessary to use the third instrument to measure the phase difference. The normal practice, however, is to combine these three instruments in one which will give a direct reading of power in watts.

### III. Answer the following questions.

1. What does the ammeter measure?
2. In what scales are graduated?
3. What does the voltmeter measure?
4. The calibration of voltmeters is usually in volts, millivolts, or microvolts, isn’t it?
5. What is the difference between the two instruments of the same type?
6. How is voltmeter connected?
7. What does the wattmeter measure?
8. What is necessary to use to measure a.c. power correctly?

### IV.Translate the text.

Електроінструменти: як правило, в інструментах електрика використовується для вироблення механічної енергії, проте є такі інструменти, які виробляють теплову енергію: паяльник, калорифер.

### V. Translate from English into Ukrainian.

To measure the current, calibrated in amperes, to measure the potential difference, the calibration of voltmeters, negative lead, a low resistance coil, an appreciable amount of power, the resistance of the operating coil, a drop in potential, the measurement of the power, a.c. power, to measure the phase difference, the instantaneous values.

### VI. Complete the sentences using the appropriate variants.

Microamperes negative lead microvolts a circuit be as high as possible a d.c. circuit a circuit
1. The calibration of voltmeters is usually in volts, millivolts or ………………………………
2. Voltmeters are used to measure the potential difference between two points in ……………
3. Scales are graduated or calibrated in amperes, milliamperes or ……………………………..
4. An ammeter is connected in the positive or …………………………………………………
5. The resistance of the operating col must …………………………………………………….
6. Ammeters measure the current flowing in ………………………………………………….
7. The measurement of the power in ……………….at any instant can be achieved by means of an ammeter and voltmeter.