Prinsip Kerja Ammeter dan Jenis-jenis Ammeter

Bayanin Ammeter

Kamar yadda a sani, sunan "meter" ana da mu'amala da tsarin kimiyyar. Meter shi ne aikin da zai iya kimiyyar hanyar na musamman. Kamar yadda a sani, tsohon karamin shine Ampere. Ammeter ya nufin Ampere-meter wanda ke kimiyyar ma'anar Ampere. Saboda Ampere ne tsohon karamin, ammeter ya fi tsaye cewa meter ko aiki wanda ke kimiyyar karamin.

Tsarin Amfani da Ammeter

Tsarin ammeter mafi so kuwa ake da takwadu da kyau da kuma inductive reactance da kyau. Idan haka, me kana so kuwa? Ba zan iya ajiye ammeter a fadin? Amsa a nan shine cewa ake da takwadu da kyau saboda ake bukata zuwa voltage drop da kyau a cikinsa, kuma ya kamata a jiye a series connection saboda karamin ce ta dace a cikin circuit na series.

Saboda takwadu da kyau, za a samu karfin gwaji da kyau, kuma idan a jiye a fadin, zai zama path na short circuited kuma duk karamin zai ci gaba a cikin ammeter, kafin ya haɗaɗa karamin da kyau, zai iya sautar aikin. Saboda haka, ya kamata a jiye a series. Don ammeter mai ban sha'awa, ya kamata ake da takwadu zero don haka za a samu voltage drop zero, kuma karfin gwaji a cikin aikin za a samu zero. Amma ban sha'awa ba a yi da shiga ba.

Matsayin ko Turutan Ammeter

Daga baya, akwai abubuwan ammeter da ake samu, su ne –

1. Permanent Magnet Moving Coil(PMMC) ammeter.

2. Moving Iron (MI) Ammeter.

3. Electrodynamometer type Ammeter.

4. Rectifier type Ammeter.

Daga baya, idan ake yi kimiyyar hanyar turutan, akwai –

1. DC Ammeter.

2. AC Ammeter.

DC Ammeter suna da PMMC instruments, MI zai iya kimiyyar AC da DC karamin, Electrodynamometer type thermal instrument zai iya kimiyyar DC da AC, induction meters ba a yi da shiga ba saboda haraji mai yawa, inaccuracy a kimiyyar.

Bayanin Abubuwan Turutan Ammeters

PMMC Ammeter

Principle PMMC Ammeter:
Idan ake jiye karamin a conductor da ake baka a magnetic field, mechanical force zai gudanar da conductor, idan ake jiye a moving system, da movement na coil, pointer zai zuwa scale.
Explanation: Daga sunan, an samu permanent magnets da ake amfani da su a wannan measuring instruments. Yana da kyau don kimiyyar DC saboda deflection proportional to the current, kafin a kashe direction na karamin, deflection of the pointer zai kashe, kuma an yi da shiga don kimiyyar DC. Wannan irin aikin ana nufin D Arnsonval type instrument. An samu linear scale, low power consumption, high accuracy. Mafi kyau shine kimiyyar DC quantity, haraji mai yawa, etc.
Deflecting torque,

Where,
B = Flux density in Wb/m².
i = Current flowing through the coil in Amp.
l = Length of the coil in m.
b = Breadth of the coil in m.
N = No of turns in the coil.
Extension of Range in a PMMC Ammeter:
An samu range of measurement a wannan type of instrument. Akwai masu yanayin da ke so kuwa ake buƙaci ammeter don kimiyyar karamin mai yawa, kuma akwai wasu da ke so kuwa ake yi da shiga constructional feature, amma ba haka, ake buƙaci shunt resistance in parallel kuma range of that instrument zai yin, wani halin da ake bayar da ita.

In the figure I = total current flowing in the circuit in Amp.
Ish is the current through the shunt resistor in Amp.
Rm is the ammeter resistance in Ohm.

MI Ammeter

Shi ne moving iron instrument, an amfani da shi don AC da DC, an amfani da shi don biyu saboda deflection θ proportional square of the current, kafin a kashe direction na karamin, yana nuna directional deflection, further they are classified in two more ways-

1. Attraction type.

2. Repulsion type.

Its torque equation is:
Where,
I is the total current flowing in the circuit in Amp.
L is the self inductance of the coil in Henry.
θ is the deflection in Radian.

1. Attraction Type MI Instrument Principle:
   Idan ake jiye unmagnetised soft iron a magnetic field, zai gudanar da coil, idan ake jiye a moving system and current is passed through a coil, it creates a magnetic field which attracts iron piece and creates deflecting torque as a result of which pointer moves over the scale.

2. Repulsion Type MI Instrument Principle:
   Idan ake jiye two iron pieces da same polarity by passing a current than repulsion between them occurs and that repulsion produces a deflecting torque due to which the pointer moves.
   The advantages of MI instruments are they can measure both AC and DC, cheap, low friction errors, robustness etc. It is mainly used in AC measurement because in DC measurement error will be more due to hysteresis.

Electrodynamometer Type Ammeter

This can be used to measure both i.e. AC and DC currents. Now we see that we have PMMC and MI instrument for the measurement of AC and DC currents, a question may arise – “why do we need Electrodynamometer Ammeter? If we can measure current accurately by other instrument also?”. The answer is Electrodynamometer instruments have the same calibration for both AC and DC i.e. if it is calibrated with DC, then also without calibrating we can measure AC.

Principle Electrodynamometer Type Ammeter:
There we have two coils, namely fixed and moving coils. If a current is passed through two coils it will stay in the zero position due to the development of equal and opposite torque. If somehow, the direction of one torque is reversed as the current in the coil reverses, an unidirectional torque is produced.
For ammeter, the connection is a series one and φ = 0
Where, φ is the phase angle.

Where,
I is the amount of current flowing in the circuit in Amp.
M = Mutual inductance of the coil.
They have no hysteresis error, used for both AC and DC measurement, the main disadvantages are they have low torque/weight ratio, high friction loss, expensive than other measuring instruments etc.

Rectifier Ammeter

Principle of Rectifier Ammeter:
They are used for AC measurement which is connected to secondary of a current transformer, the secondary current is much less than primary and connected with a bridge rectifier to a moving coil ammeter.

Advantages:

1. It can be used in high frequency also.

2. Uniform scale for most of the