Signal/Power Ground - Bartington Mag-03 Operation Manual

The current drain is independent of the power supply voltage and the unit will operate with supply
voltages down to ±8V. For a unit with a full scale range of ±100mT the output voltage for each axis
is 0.1V/mT of the field in the direction of that axis. As the output voltage swing is limited to slightly
less than the supply voltage, for a supply of ±8V the output will operate normally with any output
between +7.3V and -7.3V representing a field of 0.73 of the full scale value in each direction. The
scaling factor and linearity will remain at the normal value up to this saturation point. The output
will remain at the saturation level if the field is increased beyond this point.
Asymmetric supplies may be used provided that the minimum and maximum voltages are not
exceeded for either polarity.

10.4. Signal/Power Ground

Note: The two signal/power ground conductors are connected to a common point within the
sensor, and the power supply common (power 0 V) should be connected to only one of them.
The other signal/power ground conductor should be used as the signal output common (0V).
Each signal is then measured between the signal output conductor and the signal output
common. In this way, the signal output common carries no power supply currents.
Note: On long cables, the minimum current in the power ground conductor will give rise to
an appreciable potential difference between the power supply end and the sensor end of
the power ground conductor. The use of separate power and signal ground conductors will
ensure that this voltage is not included in the voltage measured between the signal output
and the signal common.
The product brochure shows the voltages between sensor and power supply. To ensure that the
power supply return current does not affect the analogue measurements in any way, observe the
following precautions:
A. A signal common line, separate from the power common line, should be connected between the
Mag-03 magnetic field sensor and any measurement or data acquisition system.
B. If the signal ground line is to constitute a system ground point then a fully floating power
supply must be employed, e.g. a pair of batteries or a fully isolated power supply. A number of
commercially available dc to dc converters fulfil the voltage isolation requirement adequately.
For this arrangement, only single ended analogue inputs to the data acquisition system are
required for the three axes.
C. If the power supply is to constitute a system ground point then the data acquisition analogue
inputs must be of the differential type. Each differential input can then be connected between
the remote end of the signal common line and the individual analogue outputs.
D. The above considerations also apply if more than one Mag-03 sensor is used.
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