Operation; Magnetic Field Measurements - TTI i-Prober 520 Manual De Instrucciones

Controls
The following controls are mounted on the control box.
Mode Switch
This three position slide switch adjusts the probe gain to obtain calibrated results in the three main
operating circumstances:-
FIELD
PCB TRACK Measurement of the current in a PCB track underneath the probe tip.
WIRE
Sensitivity
This control is active in the PCB TRACK position only, and is used to adjust the gain to suit the physical
width of the track being measured.
Trace position
This control adjusts the DC offset in the output signal to compensate for fields such as the earth's
magnetic fields. At high sensitivities this control has much more range than the Y position control of most
scopes.
Bandwidth Switch
This three position switch allows the user to choose the best compromise between signal bandwidth and
noise level. The three bandwidths are nominally 5MHz, 500kHz and 2Hz. The 2Hz position will almost
totally remove any visible effect of mains frequency fields at 50 or 60 Hz, but note that it is possible for the
probe to be invisibly overloaded by a large field at frequencies above the bandwidth limit.
Calibrator Switch
With the probe inserted into the calibration hole until it contacts the PCB it is subjected to the field from a
known current. The three position switch allows the selection of an AC (1kHz square wave) or DC current,
with the centre position being off. The procedure for using this to calibrate the sensitivity of the probe to
suit a particular track width is detailed below.
The calibration current should be switched off when not in use.
Overload indicator
The overload indicator will light either if the signal exceeds the clipping level of the output amplifier, or if
the magnetic field is so large that the system is saturated, which can cause the output signal to appear to
be within the operating range. In particular, this indicator should be monitored if AC coupling is used on
the scope, as it is still possible for DC fields to overload the probe.

Magnetic Field Measurements

The magnetic field is measured along the wider dimension of the probe tip. The scaling factor is 250µT
(micro-Tesla) per Volt, so the normal scope setting sequence gives 250µT/div at 1V/div, 500µT/div at
2V/div, and 1.25mT/div at 5V/div. More sensitive decades scale as expected. 250µT is 2.5 Gauss.
Alternatively the scale factor can be regarded as 200 Amps-per-metre per Volt, so the corresponding
scale factors are 200A/m/div, 400A/m/div and 1000A/m/div.
In either case the maximum output voltage is ±10V, corresponding to the maximum working field of
±2.5mT or ±2000A/m.
If the probe is held tip down (handle uppermost) with the
to give a positive output voltage, then the lines of flux are passing from a North pole on the left to a South
pole on the right. In the earth's magnetic field this means that geographic North is on the right.
Measurement of magnetic field.
Measurement of the current in a wire or cable, in conjunction with the toroid
attachment.
+
sign on the barrel facing the user, and oriented

Operation

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