Introduction

Magnetic susceptibility corresponds to the ability of a material to be magnetized in an external field. Bulk (volume) susceptibility χ_vol can be directly related to the relative permeability (μ_r ) of a material: χ_vol = μ_r - 1 and where μ_r is the ratio of permeability of material/permeability of vacuum.

Figure 1. Magnetic susceptibility of common rocks (from Bartington User Manual)

Instrument settings

Instrument units 

The instrument is pre-set to display the susceptibility value directly in either SI or CGS units.

Numerical conversion from SI to CGS units (Table1) is accomplished by dividing the SI value by 4π, i.e. χ_CG = χ_SI/4π. The MS2 meter performs this function internally but by using the constant 0.4π to keep the numbers in a similar range of magnitude.

Table 1. Mass and volume magnetic susceptibility in SI and CGS units (from Bartington User Manual)

Instrument range selection

The instrument is pre-set to display the susceptibility value in either the 1.0 or 0.1 range. Table 2 shows the exponent value of the least significant digit (i.e. the last digit on the LCD) for each range. The units in Table 2 is for volume susceptibility.

Table 2. Exponent values for least significant digit in 1.0 and 0.1 ranges (from Bartington User Manual)

On the 0.1 range a decimal point will be displayed, effectively moving all the digits on the LCD to the left when compared with the 1.0 range. It should also be noted that one measurement in the 0.1 range will be an average of multiple readings taken over a period of 10 seconds.

MS2 Meter

The MS2 meter has front panel controls (Figure 2) and a rear panel (Figure 3).

Front panel (Figure 2):

1. ‘Measure’ push button, labelled ‘M’: permits sample readings to be taken.
2. Toggle switch: performs the same function as the push button but permits continuous measurements.
3. ‘Zero’ push button, labelled ‘Z’: permits ‘air’ readings to be taken. By performing a measurement to ‘air’ this control re-sets the instrument and brings subsequent measurements within the range of the display.
4. On/Off Switch: controls the internal battery supply and also permits the selection of either SI or CGS units.
5. Range multiplier switch: allows selection of either x1 or x0.1 sensitivity range. In the second case the result is shown to the first place of decimal and a 10-fold increase in measurement time provides additional noise filtering. The switch also activates the battery indicator.

Figure 2. MS2 meter, front panel.

Rear panel (Figure 3):

1. Power supply connector: the power adaptor plug should be inserted here.
2. RS-232 serial interface: an MS2 RS-232 cable can be inserted here and connected to a computer to allow control and communication using Bartsoft software.
3. Three-way rotary Switch: allows the user to select one of three RS-232 communication settings options.
4. Charging light: this LED will light up when power is connected and the MS2 battery is being charged.

Figure 3. MS2 meter, rear panel.

Taking measurements

Connecting a sensor

Connect the sensor to be used to the front panel socket of the MS2 meter with the supplied 50Ω TNC-TNC cable, and switch on by selecting either SI or CGS units (Figure 4).

Figure 4. Connecting a sensor to the MS2 meter

Calibration

Measuring a sample