TECHNICAL DESCRIPTION AND OPERATING MANUAL ST131 <PIRANHA II> and ST131N
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4.4.4 OPERATION WITH MAGNETIC FIELD SENSOR ST131.MF.
Select
the
working
range
(0.01-31.25
KHz)
rotating
the
rotary
knob.
Operation is possible in two modes:
-
MAGNETOMETER (mode switch in position «MAG»)
-
DIFFERENTIAL (mode switch in position «GRD»)
4.4.4.1 "MAGNETOMETER" MODE.
In "MAGNETOMETER" mode the measurements produced of strength (induction) of the
magnetic field.
H = U/S (1)
B = 4pi*(10^-7)*H (2), where
U - output voltage;
S - conversion efficiency;
H - the magnetic field strength, A/m;
B – electromagnetic induction, T.
Output voltage is proportional to cos(φ), where φ - angle between the magnetic field intensity
vector and the magnetic axis.
4.4.4.2 "DIFFERENTIAL" MODE.
In the "DIFFERENTIAL" mode, field intensity difference is measured at two points on the
magnetic axis disposed symmetrically about the center.
In this mode the effect of distant powerful magnetic fields are significantly attenuated as well
as the influence of other interfering influences (acoustic, vibro-acoustic, etc.). Characteristic of this mode
is the attenuation coefficient of the homogeneous magnetic field (K).
K = 20lgU/Ug, (3), where
U - measured voltage in the "MAGNETOMETER" mode;
Ug - measured voltage in the "DIFFERENTIAL" mode.
In the frequency range of 0.3–100 KHz the value of K is over 30dB.
Using the ST131.MF sensor mainly due to the search of low-frequency spurious electromagnetic
radiation arising from the work of various electronics and office equipment (computers, communication
devices, sound systems, tape recorders, telephones, etc.).
Despite the high sensitivity of the sensor, the distance between the sensor and the examined
object should be as small as possible, almost until touching. Inspection should be done by moving the
probe along the surface of the object with the change of the spatial position.
The main variant of control is the sound through headphones.