Bartington MAG-03PSU, Operation & Maintenance Manual

Page: 4 / 21

OM0065 ISSUE 5 PAGE 4 of 21
1 INTRODUCTION
This manual describes the operation and maintenance of the
Mag -03PSU power supply unit. The
unit provides a battery backed power supply of
±
12 V for the Mag -03 series of three axis fluxgate
magnetic sensors. It also contains filters for the analog outputs of the sensor. The connector pin
allocation details are given in section 14 SPECIFICATIONS.
2 POWER
The
Mag -03PSU contains a 6 V, 1.1 Ah rechargeable battery. The battery is charged from the
240 V ac or 120 V ac mains adaptor supplied which provides a supply of 12 V dc. The battery
may be charged either intermittently or continuously, with the
Mag -03 sensor switched on or off.
The battery charger input to the power supply unit accepts a supply of 6 to 18 V dc and the
battery is charged via a temperature compensated constant voltage charger. A low battery alarm
sounds for a short period at switch-on and continuously if the battery voltage is below 5 V.
The
±
12 V supply for the Mag -03 series of magnetic field sensors is provided from the filtered
output of an isolated dc to dc converter rated at 1 W. The Mag -03PSU is connected to the Mag -
03 sensor through a 6 conductor cable, the screen of which is used for the 0 V power supply
return (common) line. (See Figure 1)
3 FILTERS
A low pass and a high pass filter are included in each of the channels for the signals from the X, Y
and Z axes of the sensor. The low pass filters provide a frequency response from dc to 4.5 kHz.
These filter remove the high frequency noise components of the signal from the sensor.
The high pass filters have a fixed low frequency cut off at 0.1 Hz and are intended to isolate the dc
or static field component so that the alternating components above this frequency can be measured
or analysed. Should static field measurements be of interest these filter sections can be linked out
using an internal jack. The enclosure of this unit has a two part construction and the lid can be
removed to gain access to these links. Instructions on filter selection are included on the inside of
the lid. (See Figure 4)
4 BUFFERS
After filtering, each analog signal is fed to the appropriate BNC connector via a low impedance
buffer. These buffers allow long cables and low input impedance data acquisition systems to be
used. The load should not be less than 1kohm resistance or greater than 200pF.
The output common return is also buffered to eliminate crosstalk due to signal currents sharing
the Va common return. A high impedance ac path is also provided between the Va common and
cable screen to improve ac noise performance.