3.1 SWITCHING ON
A short press on the ON/OFF key will turn the device on. The operating mode which was active when the device was last used, will be reactivated. A longer press of the button will turn the device off.
NOTE: If no measured value is recorded above 12.6 A/cm for about 5 minutes after switch-on, the device will switch off automatically.
3.2 BACKLIGHT
Once the device is turned on, a short press on the ON/OFF key will activate the backlight of the LCD display.
NOTE: using the backlight will significantly reduce battery life.
3.3 DISPLAY AND OPERATING ELEMENTS
Setup
Press and hold down the MODE (or RMS/PEAK) and ON/OFF keys together for approx. 2 seconds. This will take you to the setup menu so you can set the following:
Functions:
- RMS, PEAK, DC
- RMS, PEAK, DC, MAX, MIN
Measurement units: A/cm, kA/m, mT, G, Oe Press the MODE or RMS/PEAK key to cycle through the settings; select them by pressing the ON/OFF key. To cancel setup without saving any changes, press HOLD/RESET key.
NOTE: the LCD display backlight remains activated during setup.
RMS
The RMS function measures the true effective value (True Root Mean Square) of the magnetic field. The smallest measurable field strength in RMS mode is 2 A/cm; smaller field strengths will be displayed as ”<2 A/cm“.
NOTE: RMS will often only display the effective value of the alternating field proportion. The term ‘True RMS’ has been adopted here to differentiate the measurements in an arbitrary mixed field.
PEAK
The PEAK function displays the highest values of the positive or negative peak values for the actual magnetic field without a sign. This allows a quick assessment of the maximum field strength without considering the polarity.
DC
Displays the DC field proportion of an existing mixed field (the calculated median). This is an arithmetical median for symmetrical, alternating field parts which are displayed by a rotary coil instrument.
MAX/MIN
MAX: displays the maximum magnetic field strength value.
MIN: displays the minimum magnetic field strength value.
Magnetic field strength units
- A/cm
- kA/mm [1kA/m = 10 A/cm]
- Oe [1 Oe = 0.796 A/cm]
Magnetic flux density
The FSM-2 field strength meter primarily measures the magnetic tangential field strength H. It is related to the so-called magnetic flux density B according to:
B = μ0 • μr • H
Where [μ0 ] is a constant value (magnetic field constant).
The relative permeability [μr ] is dependent on the magnetic flux line of the material (μr = 1 is valid for a vacuum).
According to the above formula, the FSM-2 will convert the magnetic field strength H into the magnetic flux density B where μr = 1 will be a set value.
The following applies:
- 1 mT = 10 G (Gauss)
- 1 G ~ 0,796 A/cm ~ 1 Oe (Oersted)
Operational mode selection
With the FSM-2 in normal operating mode (not in setup mode), press the MODE or RMS/PEAK button (depending on the model) to cycle through the following display modes:
- RMS, PEAK, DC
- RMS, PEAK, DC MAX, MIN
The selected operating mode is displayed in the upper left corner of the LCD display.
Offset compensation (tare function)
A zero offset and the offset compensation are only useful for DC fields, although they must not exceed 12.6 A/cm.
To implement zero compensation, place the probe in a “field-free” location then press the HOLD / RESET button for approx. 3 seconds. Once the compensation is successfully completed, the FSM-2 will display a value of approx. 0.0 A/cm and the symbol 0-> will be displayed in the upper right corner to achieve the activated tare function.
You can now measure the changes in the magnetic field with regard to the location where the compensation was performed.
The compensation can be deactivated by pressing on the HOLD / RESET key again for approx. 3 seconds.
NOTE: the tare function can not be executed in RMS mode due to mathematical reasons.
TANGENTIAL FIELD PROBE
The tangential field probe can be permanently connected to the FSM-2 via the socket on top of the unit.
Hold the probe vertically and place the tip onto the surface being tested, ensuring that there is no gap between the sensor tip and the surface. The magnetic field component which comes into contact with the wide side of the sensor tip will be measured accordingly.
If the probe is rotated by 180° on its longitudinal axis while in DC mode, this will cause a sign reversal of the displayed value, because the magnetic field vector will now come into contact with the sensor tip on the other side.
NOTE: the sensor tip must be handled with care. It should never be used as a screwdriver or lever, as this will cause permanent damage to the sensor.
CALIBRATION
Using long-life robust components reduces the need for daily calibrating. A reference standard of 200 A/cm (part number 133042) is included to help you check the proper functioning of the device.
Tangential field probe FSM-2 with reference standard
The display accuracy of the FSM-2 should be periodically checked using a reference standard. To do this, lay the probe flat and flush with the groove of the reference standard, with the white point pointing upwards. There should be a reading of 200 A/cm ± 4% in the display. If the displayed value differs by more than 4% from the target value of 200 A/cm, send the FSM-2, with the probe and reference standard, back to Magnaflux for calibration. We recommend that you do this on an annual basis anyway.
