Voltmeter, Ammeter, Watt meter and Energy meter are four pillars of electrical energy and are most important devices used in electrical engineering field. You can't imagine any application in electrical engineering without voltage, current, energy and power measurement. Voltmeter, Ammeter, Watt meter and Energy meter connections and basics are discussed here.
If you are an electrical engineer than you must know how to connect various electrical instruments in a circuit, Specially measuring instruments. The most common instruments or measuring apparatus you must know about are Voltmeter, Ammeter, Energy meter and Watt meter.
Voltmeter : -
Voltmeter is a device that is used to measure voltage or potential difference across two given points. Essentially a voltmeter is nothing but a galvanometer with infinite resistance connected in series . This makes the resistance of an ideal voltmeter infinite .
Voltmeter is connected in parallel, this is shown below : -
As shown in image a voltmeter is connected in parallel or in shunt configuration, due to voltage division in series.
If we connect it in series high resistance of voltmeter will make the circuit insulating and no current will flow and the system will stop working.
Voltage Division in Series
If two resistances are connected in series the voltage given to the complete system is divided across resistances.
Let us consider two resistances with resistance R1
, then total resistance of series configuration will be given by
R = R1
and Voltage across each resistance is give by
is voltage across R1
is voltage across R2
The below Figure shows this more clearly.
Ammeter : -
It Measure current ( general term ) or rate of flow of charge ( Technical meaning ) between two points on a conductor.
An Ammeter is connected in series because it has low resistance and current remains same in series so the amount of current flowing through load will be same as that of Ammeter and hence Ammeter will give the exact reading. Connection of an ammeter is shown below with circuit diagram : -
Here in the circuit A is the Ammeter connected in series with Battery B and Load L to measure the current I.
Watt Meter : -
A watt meter Measures power consumed by an apparatus in a given time. Normally watt meter gives reading in watt or kilowatt.
A Wattmeter have two coils one is current coil and other is voltage coil. The power is product of Voltage across the load and current flowing through the load i.e. P=V/*I
Connection of watt meter is shown below : -
The Current coil is connected in series as current remains same in series (concept of Ammeter) and potential coil is connected in parallel as voltage remains same in parallel (concept of Voltmeter)
For Energy Meter Connection, Basics and Types visit Energy Meter: Basics and Connection in a Circuit