by MetalDetector.com Staff
If you are new tometal detecting,pipe and cablelocating orground penetrating radar, you might wonder what people mean by operating frequency. This article explains in great detail what operating frequency is and what it has to do with locating underground metal and structures. Understanding the difference between alow frequency,high frequency, multi frequency and apulseinductionmetal detectorcan seem challenging at first glance. We will demystify frequency for you. Simply stated, you can improve your searches when you use the different operating frequencies. This article will help you understand how operating frequencysignalswork ingreater depth. Understanding frequencies will help you in your search for underground utilities,coins,jewelry, gold, or other metals.
Frequency is the number of waves per unit of time measured in kilohertz or kHz. This is the number of electronic waves passed through ametal detectorinto the ground when you are detectingmetal objects.An example of 12kHz frequencyis when ametal detectortransmits and receives 12,000 times every second.If asignalrepeats itself 15 times every second, its frequency is 15 Hz.
A typicalmetal detector's best frequency forcoinsjewelryand relics is between 5 kHz to 15 kHz. This is the range where you will find mostmetal detectorsfor general-purpose are tuned. Many models will include presetsearch modesthat alter the frequency to find specific types of targets, The range is also the easiest to manage formetal detectingnewbies. More specializedmetal detectorscan be purchased once you understand the basics and begin masteringmetal detectorsearches. If you are prospecting for gold nuggets operatingfrequencies rangesignificantly higher, typically in the 17 to 70 + kHz range is ideal.
Thelower frequencythe more easily your detector will locate iron and other lower conductivity metals typically found in underground pipes and cables, and relics. The higher the operating frequency, the more easily your detector will locate high conductivity metals like gold. While wearingwireless headphonesor high qualitymetal detectingheadphones you will most easily hear thesignalsyourdevicemakes as you search for treasures. Soft or marginalsignalsproduced by yourdeviceare typically difficult to hear with out headphones.
Frequency and Conductivity
Allmetal objectslocated in the ground conduct electricity in some way with different types ofmetal detectors. AVLFstyleindustrialmetal detectorsor even ahobbymetal detectordevicewill tell you thetype of metalit has found by how well itselectronicsconduct electricity and the frequencypulsesit passes into the ground. These are determined by the speed that thesignalsent back to thedevicedecays over time. Modernmetal detectorscan discriminate between metals to identify typically on anlcd screenthetype of metalit is. They can allow you to decipher the difference betweenferrous and non ferrousby usingdiscriminationto stop thedevicefrom picking upon them.Pulseinduction and beat frequency oscillatormetal detectorsmake use of the specific frequency ofelectromagnetic fieldorpulsespassed through the ground to locate the buried target. There are different advantages and disadvantages of various frequencies used formetal detection.
Low vs.High Frequency
Lower frequenciespossess longer wavelengths. They also havegreater depthaslow frequencieshave long waves that penetrate the ground more easily thanhigh frequencies.Low frequencyis the best way for high conductivity targetdetection. Items such as silver are easier to locate usinglower frequencies. Two of the main disadvantages of usinglow frequenciesis that they are not good at locatingsmall targets. In addition, it is difficult for finding gold but best for finding iron.
High frequenciesmetal detectors workwith shorter wavelengths thanlower frequencies. These are excellent for locatingsmall targets. Items such as small gold nuggets are ideal targets forhigh frequencies. Iron and ferrous metals arelow conductivitytargets andlow frequenciesare better of locating them than higher frequencies. The wavelengths achieve lessdepthwhen searching. You have a high accuracy in locating targets that are near the surface. Finally,high frequenciesare more sensitive toground mineralizationwhich can causeinterferencewhen searching. For this reason it is important toground balanceto filter out these minerals.
Metal DetectorFrequency Chart
In eachmetal detectorfrequency chartdiagrambelow, we have compared thefrequency and frequency type by technology and by brand. We have broken each chart down by Locator type, frequencydetectioncapability, sonde capability and sonde frequency.
Schonstedt Locators Operating Frequency Comparison Chart
This frequency chart above provides a detailed comparison of theSchonstedt models. By referencing this metal frequency chart you can easily select the best pipe and cable locator for your project.
Leica LocatorsOperatingFrequency Comparison Chart
This chart above provides an indepthcomparison of theLeica GeosystemsUtilityDetectionRadar, DD Utiltility Locator and Ultra Utility range ofdevices.
Goldak Locators Operating Frequency Comparison Chart
For this comparison above, we compare the options formetal detectorcoil frequency and sonde frequency for theGoldak productsrange. You can easily see theirsingle frequencyand multi frequency options.
Goldak EMS Markers & Locators Operating Frequency Comparison Chart
This finalmetal detectorfrequency chart above covers both the single and dual frequency EMS Marker and locator range ofdevices. This chart compares the unique operating frequency required for each type of utility location such as Power, Telephone andGas EMS markersetc.
Which Frequency Is Best ForMetal Detectors?
There are two types of frequencies:Single Frequencyoperation andMulti-Frequencyoperation.Single Frequencyis also known as continuous wave. It has one frequency selection and is typically found in mid frequencyVLFmetal detectorslike theGarrett Ace 400.Single Frequencyis often found in entry to mid leveldevices. Higher enddevicesmay include a range ofsingle frequencyoptions.
Multi-Frequencymodels are typically more advancedmetal detectordevices. They use more than one frequency at the same time. The first generation of these detectors used full band spectrum (FBS) frequency technology. The latest multi frequency models are fast and provide excellentdetection depth. These technologies include Fast Multi Frequency (FMF) and Simultaneous Multi Frequency (SMF). Models like TheLegend from Nokta Makroand theXP DEUS 2incorporate these newer technologies. If you are searching for underground utilities, acomplete utility locating systemthat operates at multiple frequencies may be a good option.
Location
If you are searching for targets at a deepdepth, then you want to use a low-frequencydevice. For example,coinsare usually close to the surface and have higher conductivity. The best frequency for searching forcoinsis 10 kHz and lower. If you are searching fortiny gold nuggetsor silvercoins, you will benefit frommetal detectorswith higher frequencies.
Target Size
Depending on the targetorientationin the ground, the larger objects benefit from higher frequencydevices. The best frequency to locate large objects is 7 kHz or higher. For smaller objects, the best frequency is 7 kHz or lower.Jewelryis one search item that varies in size.
Type of Metal
The frequency you choose will depend on thetype of metalyou are searching for. The best place to find ferrous metals and iron is at 10 kHz and higher. Gold can be found at 14 kHz and higher. At frequencies between 3 kHz and 7 kHz, silver,copper, andbrasscan be found. At frequencies between 4 kHz and 8 kHz, nickel andaluminumare most readily found.
Multi-Frequencyvs.Single-FrequencyMetal Detectors
The majority ofmetal detectorsaresingle-frequencydevices. They operate at only one frequency.Single-frequencydevicestypically operate at or under 10 kHz per second or above 30 kHz per second. A number of newerdevicescandetectat two or more frequencies at the same time. Thesemetal detectorsdevicesare called simultaneousmulti-frequencydetectors.Multi-frequencydetectors are reliable and more capable due to their range of targetdetection. Think ofmulti-frequencydevicesas having moresensitivitythansingle-frequencymetal detectors. Multi Frequency units are also popular for locating pipes and cables, specific frequency sondes and sewer camera frequencies. These models candetectbothlow conductivityand high conductivity targets at the same time. This offers a major step forward indetectiontechnology
What May Affect Frequency inMetal Detectors?
While ontreasure huntsor searching for buried utilities, there may be a number of factors that may affect the frequency of usingmetal detectors. When atreasure hunteror locating crew is on the lookout for items, it's possible to experienceinterferencewith the frequency due to a few things.
Ground Mineralization
Ground mineralizationhas an effect on the normal use of ametal detector.PulseInductionmetal detectorsare not affected by mineralization. However, alower frequencyis most often the best choice for a highly mineralized search area. A higher frequency will more likely be affected by the ground’s mineralization. Temperature fluctuations can also impact the frequency.Pulseinductionsends asignalto the ground via thesearch coil. Withpulseinduction (PI), a relatively powerful, momentary current magnetizes the ground. It is possible to precisely measure the time to zero volts in the absence of metal. This technology filters out or ignores the effects of soil minerals.
Search CoilSize
Formetal detectors, it is a general rule that the larger thesearch coil, the lower the frequency it produces. Conversely, the smaller thesearch coil, the higher the frequency it produces.Althoughlarge search coilsare great for ground penetration, they lacksensitivitydue to their size.Larger coils will cover a larger area with each sweep, and they will be able todetectmuch deeper objects.Smallersearch coilsare not as good at penetrating the ground as larger coils.The advantage of this is that they will have bettersensitivityand will be able to locate individual targets that are close to each other.
Concentric versusDouble-DSearch Coils
Concentricsearch coilsoffer the easiest pinpointing for beginners as they locate the target in the center of the coil. They are not as good at filtering out minerals in the grounds.Double-Dor DDsearch coilsare very good at reducing the impacts of minerals in the ground. For this reason they are the choice of most experienced users or for use in areas with lots of minerals and targets in the higherfrequency range. The DD coils pinpoint the targets closer to the heal of the coil.
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