A frequency counter is an electronic instrument, or component of one, that is used for measuring frequency. Since frequency is defined as the number of events of a particular sort occurring in a set period of time, it is generally a straightforward thing to measure it. Electronics is the controlled manipulation of the flow of electrons; as defined by KAOS, A.K.A. TCBHM, in 1974. ... Captain Nemo and Professor Aronnax contemplating measuring instruments in Twenty Thousand Leagues Under the Sea In physics and engineering, measurement is the activity of comparing physical quantities of real-world objects and events. ... Sine waves of various frequencies; the lower waves have higher frequencies than those above. ...

Hobbyist frequency counter circuit built almost entirely of TTL logic chips.

Most frequency counters work simply by using a counter which accumulates the number of events. After a preset period (1 second, say), the value in the counter is transferred to a display, and the counter is reset to zero, to begin accumulating the next sample period. If the event being measured repeats itself with sufficient stability of frequency, and this frequency is considerably lower than that of the clock oscillator being used, the resolution of the measurement can be greatly improved by measuring the time required for an entire number of cycles, rather than counting the number of entire cycles observed for a pre-set duration. The internal oscillator which enables the frequency counter to measure time is called the timebase, and must be very accurately calibrated. Image File history File links Download high resolution version (1955x1425, 350 KB) Summary This is a hobbyist-built main circuit in a 6. ... Image File history File links Download high resolution version (1955x1425, 350 KB) Summary This is a hobbyist-built main circuit in a 6. ... In general, a counter is a device which stores (and sometimes displays) the number of times a particular event or process has occurred often in relationship to a clock signal. ...

If the thing to be counted is already in electronic form, simple interfacing to the instrument is all that is required. More complex signals may need some conditioning to make them suitable for counting - most general purpose frequency counters will include some form of amplifier, filtering and shaping circuitry at the input. Other types of periodic event that is not inherently electronic in nature will need to be converted using some form of transducer. For example, a mechanical event could be arranged to interrupt a light beam, and the counter made to count the resulting pulses. The term amplifier as used in this article can mean either a circuit (or stage) using a single active device or a complete system such as a packaged audio hi-fi amplifier. ... The term filter may refer to: A device to separate mixtures. ... A transducer is a device, usually electrical or electronic, that converts one type of energy to another. ...

Frequency counters designed for radio frequencies (RF) are also common, and operate on the same principles as lower frequency counters, but often have more range before they overflow. For very high frequencies, many designs use a high-speed prescaler to bring the signal frequency down to a point where normal digital circuitry can operate. The displays on such instruments take this into account so they still read true. If the measured frequency is too high for any prescaler, a mixer and a local oscillator can produce a suitable frequency to measure. A prescalar is an electronic device - sometimes no more than a chip - that essentially takes a frequency and reduces it by a pre-determined factor. ... In telecommunications a mixer is a frequency mixer. ... The Superheterodyne receiver (or to give it its full name, The Supersonic Heterodyne Receiver – usually these days shortened to superhet) was invented by Edwin Armstrong in 1918. ...

The accuracy of a frequency counter is strongly dependent on the stability of its timebase. Highly accurate circuits are used to generate this for instrumentation purposes, usually using a quartz crystal oscillator within a sealed temperature-controlled chamber, known as a crystal oven or OCXO (oven controlled crystal oscillator). For higher accuracy measurements an external frequency reference tied to a very high stability oscillator, such as a GPS disciplined rubidium oscillator may be used. Where the frequency does not need to be known to such a high degree of accuracy, simpler oscillators can be used. It's also possible to measure frequency using the same techniques in software in an embedded system - a CPU for example, can be arranged to measure its own frequency of operation provided it has some reference timebase to compare with. Quartz is amongst one of the most common minerals in the Earths continental crust. ... A crystal oscillator (sometimes abbreviated to XTAL on schematic diagrams) is an electronic circuit that uses the mechanical resonance of a physical crystal of piezoelectric material along with an amplifier and feedback to create an electrical signal with a very precise frequency. ... OCXO (short for Oven Controlled X-tal (Crystal) Oscillator) is a technique used for avoiding temperature changes that affect the resonance frequency of a piezoelectrical crystal. ... Over fifty GPS satellites such as this NAVSTAR have been launched since 1978. ... General Name, Symbol, Number rubidium, Rb, 37 Chemical series alkali metals Group, Period, Block 1, 5, s Appearance silvery white Atomic mass 85. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Intel 80486DX2 microprocessor in a ceramic PGA package A central processing unit (CPU), or sometimes simply processor, is the component in a digital computer that interprets instructions and processes data contained in software. ...

Frequency counter manufacturers:

• Agilent Technologies
• Anritsu
• Pendulum Instruments
• Phase Matrix
• Stanford Research Systems