from Terraplus

The KT-20 offers a complete handheld solution for mineral exploration, geological sampling, core logs or soil science. The instruments ability to record Magnetic Susceptibility, Conductivity/ Resistivity, Density, Induced Polarisation and Geospatial Position enables the Exploration Geophysicists to map and characterise samples effortlessly. The KT-20 supports a number of different sensors in order for the instrument to be optimised for a particular application. Both the coil shape and frequency can be varied by changing the sensor.

KT20 with circular dual frequency coil. Image courtesy of Terraplus.

Each instrument is supplied with a pre-installed calibration curve. The conductivity calibration is based off a multi-point algorithm to ensure accurate measurements between inductive and galvanic methods. The magnetic susceptibility calibration curve is derrived from samples with containing various concentrations of magnetite, enabling the KT20 to calculate an estimated direct iron ore concentration (%). Alternatively operators are able to formulate and save their own calibration curves.

The KT-20’s unique design enables users to interchange between the circular, rectangular or large 3F-32 field coil on the fly. The circular sensor has a large surface area and is recommended for grassroots exploration and measuring samples larger than 66 mm. Conversely, the rectangular sensor is ideal for measuring cores with diameters smaller than 66 mm.

The 3F‐32 sensor has a 32 cm diameter and features three frequencies that have been carefully selected to provide certain benefits for magnetic susceptibility and conductivity measurements. The 3F‐32 sensor is equipped with a telescopic pole and arm support enabling users to easily and comfortably take measurements while standing or walking. The KT‐20 with 3F‐32 sensor is an ideal instrument for field research. It can take a single measurement at a specific location, or continuously collect data to map an entire area. A GPS receiver is integrated into the KT‐20 console to provide location coordinates with the data. It also has a built‐in high resolution digital camera to visually document any sample of interest.

The KT-20 S/C is available with two dual-frequency sensors: 1/10 kHz or 10/100 kHz. Those focusing on magnetic susceptibility measurements will benefit from the 1/10 kHz sensor because the 10 kHz frequency provides a higher sensitivity, whilst the 1 kHz frequncy reduces the influence of a sample’s conductive properties on the measurements, in addition to providing a greater depth penetration (although with a reduced sensitivity). The 10/100 kHz is advantageous for conductivity measurements because the 100 kHz frequency increases the meter’s sensitivity to 0.1 S/m, while the 10 kHz has a greater depth penetration (although with reduced sensitivity).

Induced Polarisation measurements require the samples to be placed sample holder similar to a vice. The device is portable so samples can be processed and measured at base camp. The IP/Resistivity sensor can be supplied as a Standard and Pro model.

The Standard model calculates total chargeability (M_x) using two methods: 20 windows and Mx fit. The first measures total chargeability using the traditional 20 windows method. The second, Mx Fit, is an algorithm that measures total chargeability using several thousand windows instead of 20. The benefit of Mx fit is that it provides increased accuracy and confidence in the measurements.

The Pro model enables the user to analyse decay curves with up to 16,000 data points for any measurement time. Through these data points the decay curve is studied to calculate total chargeability (M_x) and initial chargeability (M_ip). Users can also customise their own chargeability windows (M_x_user) and time periods (t1 and t2). Furthermore, an extra early delay time (as fast as 2 ms after turn-off) allows the Pro model to collect data much earlier than before, providing users with new capabilities to improve their interpretation. The KT-20 IP Pro model includes all of the same capabilities as the Standard model.

Product Dimensions

Physical Dimensions (L x W x H) Weight
KT20 (instrument only) 26cm x 7.2cm x 6cm 0.35kg

Technical Specifications

Memory: 4 GB: 4,000 Total Records Stored.
Control: 5-Button Control with LED Illumination.
Data Input/Output: USB and Bluetooth.
Power Supply: 2 x Li-Ion Rechargeable Batteries.
Operating Frequnecy: 1kHz and 10KHz Dual Frequncy Sensor.
10kHz and 100KHz Dual Frequncy Sensor.
Single frequncy sensors are also available.
Operating Temperature: -20°C to 60 °C.
Sensors: Rectangular, Circular or large 32cm coil.
Transreflective Colour Display Dimensions: 76 x 47 mm
Transreflective Colour Display Resolution: 400 x 240 pixels
Circular Sensor Dimensions: 6.6cm
Rectangular Sensor Dimensions: 6.6 (L) x 3.2 (W) cm
3F-32 Ground Sensor Dimensions: 32cm
Rating: Rating: IP65
Internal GPS Accuracy: 2.0m
Internal GPS Receiver Satellite Accessibility: SBAS (WAAS, EGNOS, MSAS).
Built-in Camera: 2 Mega Pixels.
GeoView PC Software: Supports all Windows 32 or 64 bit operating systems.
GeoVision App: Android operating system (OS) must be version 2.3.3 or higher.

Data Sheet

Application Notes

Precision agriculture

The intensive nature of agricultural farming can result in a large amount of spatio-temporal variation in soil. Magnetic susceptibility can be used to detect iron-containing minerals which are found in soil, sediment and rocks. An elevated presence of heavy metals (eg from high traffic volumes) can be detected using magnetic susceptibility measurements. These heavy metals on agricultural land can affect food quality and safety; hence this method is becoming important for monitoring environmental pollution. The magnetic properties of soils have also been linked to the organic matter content, making this of particular interest to precision agriculture farmers.

The conductivity component can provide information about soil properties that affect crop productivity. These include organic matter level, salinity and drainage conditions. The porosity and hence also the density are influential factors too, as this will determine the volume of water that can be held in the pores. And finally the measured conductivity may be affected by colloids, specifically those associated with organic matter.

Mineral exploration

The KT-20 has the ability to accurately measure magnetic susceptibility, which is used extensively to determine the magnetic properties of rocks. This is vital for mineral exploration as magnetic susceptibility is related to the concentration and composition of magnetisable material contained in a sample. Magnetisable material includes magnetite, hematite, iron, titanium oxides and clay minerals (chlorite, smectite and glauconite). It can also display an estimated iron ore concentration (%) through the pre installed calibration curve.

The conductivity aspect of the KT-20 is particularly useful in mineral exploration because the target ore minerals generally have a high conductivity compared to the rock types with which they are associated. Metallic ore minerals can significantly affect the bulk resistivity/conductivity of a sample, even in small quantities.

The induced polarisation measurement with the KT-20 gives a dimensionless quantity known as chargeability. These measurements are influenced by minerals which conduct by electron flow, including pyrite and graphite. Clay minerals may also affect the IP measurements however this would be of a smaller magnitude.


Magnetic susceptibility in archaeology can be used to locate traces of previous human habitation, for example building foundations, field systems and areas of burning. The remains of a fire can affect magnetic susceptibility because silt particles and iron oxides can be transformed into very magnetic oxides through burning, and when the organic matter in soil burns it can change hematite to magnetite. Thus increased magnetic susceptibility hotspots could be due to large fires, hearths and kilns. If spikes are present in vertical sections of magnetic susceptibility data, this would indicate a burned layer. Magnetic susceptibility surveys are often used as a precursor to more in depth magnetic surveys. It is an effective way to determine areas of potential archaeological activity. The IP resistivity of samples can provide information on the presence of disturbed clay in an area which has previously been occupied by humans.


Magnetic susceptibility measurements can efficiently be used on soil and sediment samples to monitor anthropogenic pollution. These measurements can be used to identify polluted areas, and then to map these areas. Since the magnetic susceptibility is sensitive to ferromagnetic elements such as nickel, lead and zinc the KT-20 can be used to monitor pollution around industrial sites – both past and present. Heavy metal elements (iron, copper, manganese and nickel) have been shown to produce a correlation with magnetic susceptibility, indicating it is possible to use these as proxies for contamination.