A frequency meter is a device used to quantify oscillations in hertz (Hz), or the rate at which a recurring event happens. They are the indicating devices that measure the frequency of electrical energy. This electrical energy is usually created by different circuits as waves or signals.
Moving coil frequency meters operate based on differences in the electric current drawn by parallel connections between inductive and non-inductive circuits. Let’s find out more about frequency meters and their types.
Now that you know the concept, you may be eager to know the different types of frequency meters. Although different versions can be found, three types of frequency meters are more popular than others. Examples include the moving iron frequency meter, the electrodynamic frequency meter, and the vibrating-reed frequency meter.
The meters have two fixed coils and a moving iron fastened to the spindle. The following is the operating concept of these meters.
This meter depends on changes in the electric current drawn by parallel circuits that are both inductive and non-inductive. The current from these circuits flows when the frequency changes in terms of value.
The magnetic axes of the two stationary coils, A and B, which make up this frequency measurement device, are perpendicular to one another. A long, soft iron needle is pegged at their centers. This circuit maintains its balance at the supply frequency that has to be measured.
Coil A contains a sequence of resistance Ra and reactance La in parallel. Coil B includes a series of resistance Rb and reactance Lb in parallel. The series inductance reduces waveform inaccuracies in the instrument indication by suppressing higher harmonics in the current waveform.
When you connect the supply to the meter, coils A and B generate opposing torques while electricity passes through them. The current in coil A increases and it decreases in coil B in response to an increase in supply frequency. The iron needle is located closer to coil A’s magnetic axis. For low frequencies, coil A’s current reduces and coil B’s current increases.
These meters measure very small amounts in addition to measuring massive levels of frequency.
Moving coil frequency meters or electrodynamic frequency meters are ratiometer types of instruments. These meters are employed to determine the frequency of both excessively low and high voltage ranges. They offer accurate frequency readings and are made up of a rectifier circuit and two moving coils.
This frequency meter has two moving coils connected and positioned to each other at right angles on a shaft. Also, a pointer is attached to this shaft. The bridge rectifiers of these two moving coils are coupled. The bridge rectifier of the first moving coil, C1, which is coupled to the DC supply, is connected in series with a capacitor in this circuit. Direct current, also known as rectified current, travels to the bridge rectifier and the second coil C2 via a series resistance.
These meters rely on a capacitor and resistance value. The ranges of these frequency meters are 40–60 Hz, 1200–2000 Hz, and 8000–12000 Hz. Now, let us see how frequency is measured with this device.
When you connect the frequency to the supply, the rectified currents I1 and I2 pass through the moving coils C1 and C2. These coils’ torques become equal but point in different directions when they reach their rest positions.
These frequency meters provide a large voltage range as well as a low voltage range of operation.
The distortions that rectifiers produce lead to an incorrect frequency measurement.
It is an instrument used for measuring the frequency of different electric circuits. It contains seven vibrating reeds. Each reed has a distinct value. These reeds vibrate when you connect the meter to the supply for frequency measurement. Each reed has variations in vibration. A reed with more vibration compared to other reeds is considered the frequency reading of an electric circuit or supply.
This meter contains thin flat steel reeds positioned alongside and close to the electromagnet. A laminated armature and a winding coupled to a resistance in series make up the electromagnet. The AC supply, whose frequency has to be monitored and measured, stays connected to this winding. The metallic reeds are 0.5 mm thick and 4mm wide.
These metal reeds are placed in a row and have flexible bases that support the electromagnet’s armature. The color of these reeds is white. On a scale, these reeds remain grouped according to increasing frequency.
The frequency readings on these vibrating reed metros range from 47 Hz to 53 Hz and 57 Hz to 63 Hz.
It is necessary to connect the meter to a supply to measure the circuit’s frequency. The supply that will be used for measuring frequency stays connected to the electromagnet. Every half cycle, the electromagnet applies an attracting force to every reed since its magnetism alternates at the same frequency.
Each reed begins to vibrate, but due to mechanical resonance, the reed with the double frequency vibrates at its highest amplitude. The vibration of other reeds is so small that they are unobservant.
These measuring devices have an array of uses in different sectors. For example, many businesses use industrial frequency meters in radio frequency and microwave applications to tune transmitters and display rapidly changing frequencies.
Companies that use radio devices employ frequency meters to figure out the exact pitch of the instrument. Similarly, these devices have their uses in power applications to tune AC motors as well as other AC devices.
Frequency meters have become an integral part of our lives. From microwave devices to power applications, we have these useful measuring instruments for our betterment. If you are out in the market to buy a gadget featuring a frequency meter, check its power, abilities, and accuracy to make the best out of the item you choose.
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1. Who uses frequency meters?
Communication engineers and electrical engineering businesses wisely use these measuring devices.
2. How to buy the right frequency meter?
Accurate frequency measurement is critical to maintain the performance of electrical systems. So, look for a device with high resolution and better accuracy to ensure precise readings. Additionally, check the warranty and ease of usage options.
3. What are the uses of a digital frequency meter?
A digital meter is a general-purpose instrument that shows the frequency of an electrical signal to an accuracy of three decimal places. It counts the number of events occurring within the oscillations during a given time interval
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