1. An electronic energy meter makes use of _______

IC

Transformer

CRO

Multimeter

Answer.1. IC

Explanation:

Electronic Energy Meter is based on Digital Micro Technology (DMT) and uses no moving parts. So the EEM is known as “Static Energy Meter” In EEM the accurate functioning is controlled by a specially designed IC called ASIC (Application Specified Integrated Circuit).

The basic IC incorporated in the electronic meter is SA2007P. The SA2007P is CMOS mixed-signal A/D integrated circuit that performs energy as well as power calculations.

2. Full load Unity power factor adjustment in energy meter involves _________

Adjusting the loads at unity power factor

Applying rated voltage to pressure coil and a p.f. of unity for current coil

Only applying rated voltage to pressure coil

Only a p.f. of unity for the current coil

Answer.3. Only applying rated voltage to pressure coil

Explanation:

Full load Unity power factor adjustment in energy meter involves applying rated voltage to pressure coil. The current coil is provided with a current at the unity power factor. Rated voltage is applied to the pressure coil. Errors are kept minimum and the position of the brake magnet is so adjusted that the disc rotates at the correct speed.

3. In electronic energy meter the measurement of energy involves _________

Inductance and capacitance measurement

Power consumption and time duration

Resistance measurement and voltage drop

Current consumption and voltage drop

Answer.2. Power consumption and time duration

Explanation:

In an electronic energy meter, the measurement of energy involves power consumption and time duration.

The measurement of energy can be divided into two parts. Basically, energy is defined as the total power delivered or consumed over a time period. So the measurement of energy can be done by measuring the power and time over which it is consumed.

4. Low power factor adjustment in energy meter involves _________

The power factor at lower loads

Rated voltage to pressure coil and a p.f. of 0.5 for current coil

Applying rated voltage to pressure coil

p.f. of 0.5 for the current coil

Answer.2. Rated voltage to pressure coil and a p.f. of 0.5 for current coil

Explanation:

Low power factor adjustment in energy meter involves applying rated voltage to pressure coil and a p.f. of 0.5 for the current coil.

This compensation is provided to overcome the errors due to incorrect phase angle between the supply voltage and shunt magnet flux φp.

Rated voltage is applied to the pressure coil. The current coil is provided with a current at 0.5 p.f. lagging. Till the disc rotates at the correct speed, the lag device is adjusted.

5. Average power in electronic energy meter is _________

Product of voltage and current

Product of average current and voltage

Product of instantaneous voltage and current

Product of absolute voltage and current

Answer.3. Product of instantaneous voltage and current

Explanation:

In an electronic energy meter, the average power is equal to the voltage across the load and instantaneous current through it.

By using a potential divider, the supply voltage is brought to the required level.

This voltage is then scaled appropriately in the required range by using a voltage scaling device. While the current scaling device scales the load voltage which is proportional to the load current.

6. Light load adjustment in energymeter involves _________

Applying rated voltage across the pressure coil

Adjusting a light load

Applying rated current across the transformer

Applying rated voltage across the current coil

Answer.1. Applying rated voltage across the pressure coil

Explanation:

Inspite of the proper design of the bearings and registering mechanism, there is bound to exist some friction. Due to this, the speed of the meter gets affected which causes the error in the measurement of the energy.

Disc rotation of the energy meter is adjusted in such a way that the correct speed is maintained. The pressure coil is supplied with the rated voltage and the current coil is provided with only about 5 % of the full load at u.p.f.

7. What is the role of a multiplier in an electronic voltmeter?

It multiplies the voltage and frequency

Divides the alternating voltage and current

Supplies instantaneous voltage and current

Multiplies alternating voltage and current

Answer.4. Multiplies alternating voltage and current

Explanation:

In an electronic energy meter, the average power is equal to the voltage across the load and instantaneous current through it.

By using a potential divider, the supply voltage is brought to the required level.

This voltage is then scaled appropriately in the required range by using a voltage scaling device. While the current scaling device scales the load voltage which is proportional to the load current.

Both these scaled voltages are connected to voltage and current multiplier units. This unit outputs the current as a result of the product of a.c. voltage and current. The current is proportional to the load and depends on line voltage hence remains constant.

8. The digital data in the Electronic voltmeter is converted into

Power Value

Average Value

Digital Value

Instantaneous Value

Answer.2. Average Value

Explanation:

In an electronic voltmeter, the ‘Input Data’ (Voltage) is compared with a programmed “Reference Data’ (Voltage) and finally a ‘Voltage Rate’ will be given to the output. This output is then converted into ‘Digital Data’ by the AD Converters (Analogue- Digital converter) present in the ASIC.

The Digital Data is then converted into an “Average Value”. Average Value / Mean Value is the measuring unit of power. The output of ASIC is available as “Pulses” indicated by the LED (Light Emitting Diode) placed on the front panel of the electronic energy meter.

9. Frequency of oscillation in an electronic energy meter depends on __________

Output current of multiplier

Output voltage of multiplier

Output power of multiplier

Input resistance of multiplier

Answer.2. Output current of multiplier

Explanation:

In an electronic energy meter, the average power is equal to the voltage across the load and instantaneous current through it

As the voltage-controlled oscillator is basically voltage to frequency converter, it produces a square wave output.

The frequency of this square wave is proportional to the output current of the voltage-current multiplier.

Thus the power-dependent current and the frequency-dependent current decide the value of the consumed energy.

10. The advantage of the electronic energy meter is

High sensitivity

No friction loses

less loading effect

All of the above

Answer.4. All of the above

Explanation:

The advantages of the electronic energy meter are as follows :

High sensitivity

No friction losses

Less loading effect

Low load, full load, power factor, and creeping adjustments are not required.