Ammeter Design A meter designed to measure electrical current is popularly called an "ammeter" because the unit of measurement is "amps." In ammeter designs, external resistors added to extend the usable range of the movement are connected in parallel with the movement rather than in series as is the case for voltmeters.
Full Answer
What makes a good ammeter?
An ideal ammeter has zero resistance. A “clamp-on” ammeter measures current through a wire by measuring the strength of the magnetic field around it rather than by becoming part of the circuit, making it an ideal ammeter.
How is an ammeter designed?
Ammeters, as well as voltmeters and ohmmeters, are designed with the use of a sensitive current detector such as a galvanometer. An ammeter is placed in series with a circuit element to measure the electric current flow through it.
What does an ammeter tell us about a circuit?
An ammeter (abbreviation of Ampere meter) is an instrument used to measure the current in a circuit. Electric currents are measured in amperes (A), hence the name. For direct measurement, the ammeter is connected in series with the circuit in which the current is to be measured.
Does a good ammeter have high resistance?
Hence, voltmeter have very high resistance, and an ammeter have low resistance for accurate measurement of potential difference and current should be used.
What factors affect the accuracy of the ammeter readings?
Factors That Affect The Accuracy of MeasurementsWrong values. Calibration of any instrument must be completed exactly as instructed. ... Wrong calibrator. ... Ambient conditions.
How do you determine the resolution of an ammeter?
2:274:37Resolution of Instrument l How to Determine Resolution l Electrical ...YouTubeStart of suggested clipEnd of suggested clipNow one scale division is equal to 1 divided by 5 that means 0.2 ampere now the instrument can readMoreNow one scale division is equal to 1 divided by 5 that means 0.2 ampere now the instrument can read up to 1 4th of scale division that means 0.2 into 1 by four zero point zero five ampere.
How does an ammeter affect the circuit being measured?
Ammeters measure the current through components. To measure the current going through a component, the ammeter is connected in series with the components we want to investigate. Resistors in series experience the same current (Figure 3). Typically, ammeters have negligible resistance, so they do not affect the circuit.
How does an ammeter determine amperage?
Ammeter Function Ammeters work to measure electrical current by measuring the current through a set of coils with a very low resistance and inductive reactance.
What is the reading accuracy of ammeter?
A 0 - 10 A ammeter has a guaranted accuracy of 1.5% of full scale reading. The current measured by the instrument is 2.5 A.
Should an ammeter have a high or low resistance?
An ammeter is an instrument for measuring the electric current in amperes in a branch of an electric current. It must be placed in series with the measured branch, & must have very low resistance to avoid significant alternation of the current it is to measure.
Why is it that an ammeter was designed with low resistance?
If the resistance of the ammeter would be high, the total resistance would be high. This would decrease the amount of current flowing through the circuit. Hence, in order to avoid the change of current flowing in a circuit. The resistance of an ammeter should be as small as zero.
Does an ammeter have high or low resistance?
Hint: Ammeter is a device which is used to measure the amount of current passing through the circuit, and it is connected in series with the circuit. As stated, the ammeters have low resistance.
What is the diagram of ammeter?
In circuit diagrams, the symbol for an ammeter is a circle with a capital A inside. Ammeters vary in their operating principles and accuracies. The D'Arsonval-movement ammeter measures direct current flowing through a coil suspended between the poles of a magnet with accuracies of from 0.1 to 2.0 percent.
How do you make a dc ammeter?
If we place a resistor in parallel with the Permanent Magnet Moving Coil (PMMC) galvanometer, then the entire combination acts as DC ammeter. The parallel resistance, which is used in DC ammeter is also called shunt resistance or simply, shunt.
What is the formula of ammeter?
i=VRTherefore the formula for the value of the electric current measured by an ammeter is i=VR. Note:Ohms law states that the current though a conductor is directly proportional to the potential difference provided the temperature remains the same. It is to be noted that a galvanometer can also be used as an ammeter.
How do you write current meter?
DIY Current Meter Using ArduinoSupplies. Components required: ... Step 1: Story. There are many methods to measure the DC current. ... Step 2: Shunt Resistor: ... Step 3: Amplification: ... Step 4: Amplification Factor Calculations: ... Step 5: Why 1volt for 1ampere: ... Step 6: Circuit Diagram: ... Step 7: PCB Files:More items...
Why do ammeters have resistors?
Ammeter Design. In ammeter designs, external resistors added to extend the usable range of the movement are connected in parallel with the movement rather than in series as is the case for voltmeters. This is because we want to divide the measured current, not the measured voltage, going to the movement, and because current divider circuits are ...
Why do ammeters have parallel resistance?
This is because we want to divide the measured current, not the measured voltage, going to the movement, and because current divider circuits are always formed by parallel resistances.
Where is the shunt resistor on an ammeter?
In real life, the shunt resistor of an ammeter will usually be encased within the protective metal housing of the meter unit, hidden from sight. Note the construction of the ammeter in the following photograph:
What is the amp rating of a Stewart-Warner meter?
Although the D’Arsonval meter movement itself probably has a full scale rating in the range of milliamps, the meter as a whole has a range of +/- 60 amps.
What is a battery meter?
Connected to the battery charging circuit of an automobile, this meter is able to indicate a charging condition (electrons flowing from generator to battery) or a discharging condition (electrons flowing from battery to the rest of the car’s loads).
Can an ammeter have more than one range?
As is the case with multiple-range voltmeters, ammeters can be given more than one usable range by incorporating several shunt resistors switched with a multi-pole switch:
Can shunt resistors be used in real circuits?
However, such a tiny error is generally well within acceptable limits of accuracy for either a simulation or a real circuit, and so shunt resistors can be used in all but the most demanding applications for accurate current measurement.
What is Ammeter?
Ammeters were laboratory instruments that depended on the earth’s magnetic field for operation. In the 19th century, the ammeter with the ability of accurate measurements, which could be mounted in any position was invented.
Why is low resistance offered by ammeters?
Low resistance is offered by the ammeter because: Input current passes completely through the device. Low voltage drop takes place across the device. The ammeter has an inbuilt fuse that protects the device from heavy current. If substantial current flows through the ammeter, the fuse will break.
What is swamping resistance?
An ammeter is a thermally sensitive device that is affected by internal as well as external environmental conditions. Temperature contributes to the reading of the device. The resistance having a zero temperature coefficient is known as the swamping resistance. When swamping resistance is connected in series with the ammeter , it decreases the effect of temperature on the ammeter .
What is moving iron ammeter?
In the moving iron ammeter, the coil freely moves between the poles of a permanent magnet. This ammeter can measure both the alternating and direct current.
Does an ammeter have low resistance?
Ammeter always offers low resistance, and zero internal resistance is offered by an ideal ammeter. In general, it has feeble internal resistance. Low resistance is offered by the ammeter because:
Example 1: Finding the Potential Difference across Two Parallel Branches in a Circuit with a Galvanometer
The circuit diagram represents a galvanometer combined with a shunt resistor. The emf of the source connected to the galvanometer and the shunt is 3.0 V. The circuit does not represent a circuit in which the galvanometer and shunt correctly function as an ammeter.
Answer
In the diagram for this question, we have a circuit containing a galvanometer in parallel with a shunt resistor. In this case, the resistance of the galvanometer has not been explicitly included as a resistor in the circuit diagram, but we know that it does have some resistance.
Equation: The Resistance of a Shunt Resistor in an Ammeter
Suppose we have an ammeter consisting of a galvanometer with a full-scale deflection current 𝐼 and a resistance 𝑅 connected in parallel with a shunt resistor.
Example 2: Finding the Required Resistance of a Shunt Resistor in an Ammeter
A galvanometer has a resistance of 15 mΩ. A current of 125 mA produces a full-scale deflection of the galvanometer. Find the resistance of a shunt that when connected in parallel with the galvanometer, allows it to be used as an ammeter that can measure a maximum current of 12 A. Answer to the nearest microhm.
Answer
Let’s begin by drawing a circuit diagram and labeling the values that we have been given.
Equation: The Measurement Range of an Ammeter
Suppose we have an ammeter consisting of a galvanometer with a full-scale deflection current 𝐼 and a resistance 𝑅 connected in parallel with a shunt resistor of resistance 𝑅 .
Example 3: Calculating the Measurement Range of an Ammeter
A galvanometer has a resistance of 12 mΩ. A current of 150 mA produces full-scale deflection of the galvanometer. A shunt is connected in parallel with the galvanometer to convert it into an ammeter. The resistance of the shunt is 70 µΩ. What is the greatest current that the ammeter can measure? Answer to one decimal place.
What is an ammeter?
Ammeter, instrument for measuring either direct or alternating electric current, in amperes. An ammeter can measure a wide range of current values because at high values only a small portion of the current is directed through the meter mechanism; a shunt in parallel with the meter carries the . Ammeter, instrument for measuring ...
Why do ammeters measure a wide range of currents?
An ammeter can measure a wide range of current values because at high values only a small portion of the current is directed through the meter mechanism; a shunt in parallel with the meter carries the . Ammeter | measurement instrument | Britannica. BrowseSearch. QuizzesGamesOn This Day.
What is the accuracies of a thermal ammeter?
In the thermal ammeter, used primarily to measure alternating current with accuracies of from 0.5 to 3 percent, the measured current heats a thermoconverter (thermocouple); the small voltage thus generated is used to power a millivoltmeter.
