KM-7 Magnetic Susceptibility Meter

The KM-7 magnetic susceptibility meter is an easy-to-use pocket device designed for measuring the magnetic susceptibility of rocks and drill cores. It is also suitable for selection of appropriate samples for precise measurements of their magnetic properties in the laboratory.

The KM-7 measures the magnetic susceptibility in the range of ± 999 x 10-3 SI units with automatic range change. The maximum sensitivity is 1 x 10-6 SI units. It is equipped with a memory to store up to 999 records. As the KM-7 is designed for field use, it has a robust construction that is dust and water-resistant. It can be worn on a wrist strap or in a leather case on a belt.

The fundamental component of the device is an LC oscillator, where the measuring coil is in the head of the device. The measurement is performed in two steps. The frequency of the oscillator is measured with the coil located in a distance from the rock (free space measurement), and then the coil attached to the rock surface. The susceptibility of the sample is calculated from the difference of the two frequencies,

Because the frequency of the LC oscillator is temperature-dependent, a three-point measurement is performed. The first measurement is made in free space, the second on the rock sample, and the third again in the free space. Thanks to the two measurements in the free space and knowledge of the time intervals between individual measurements, it is possible to determine the influence of the thermal drift of the LC oscillator and perform its compensation. Thanks to the compensation of the oscillator thermal drift, a high resolution of the measurement can be achieved.

The measured value of the magnetic susceptibility depends on the size and shape of the measured object because the KM-7 is calibrated for the ideal case where the measuring coil is applied during calibration to an absolutely smooth surface corresponding to a half-plane with magnetically homogeneous and isotropic properties. Therefore, for measurements on rough surfaces, the KM-7 is equipped with a pin, which gives more reliable results for measurements on uneven surfaces. When measuring with a pin, it is necessary to set the sensor configuration to the PIN mode.

The KM-7 magnetic susceptibility meter is also calibrated for measurements on drill cores. Measuring on drill cores is activated after setting the sensor configuration to the CORE mode and entering the drill core diameter. However, caution should be taken when measuring directly on drill cores, as the instrument may show false results if there is a residual metal material on the surface of the drill core from a drill.

The REMOTE SCAN mode can be used to measure the profile of drill cores. In this mode of operation, measurements are performed several times per second, and the measured values are transferred directly to a computer via USB or Bluetooth.

To measure an approximated distribution of the magnetic susceptibility, the SCAN measurement mode can be used. In the SCAN mode, the magnetic susceptibility of the sample is measured 3 times per second, and its value is displayed. In this mode, the measured values are not saved.

The KM-7 enables communication with an external device using Bluetooth wireless technology. This allows the KM-7 to connect to an external GPS receiver, which can send the NMEA messages using the Bluetooth SPP protocol. If the KM-7 is connected to such a GPS receiver, the location of the sample is saved with its value.

The KM-7 is supplied with the KMdata communication program, which is used for data transfer and a graphical display of measured values. The transferred data is immediately stored in the internal database of the program, where it can be viewed and sorted. The data can also be exported into a text file, which can then be used for further processing.

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