If the distance from the sensor PCB to the bus bar is fixed the user still has the ability to vary the placement of the sensors relative to the center of the bus bar and one another. Figure 6-2 shows the errors vs the device spacing relative to the center of the bus bar. Each line represents a different distance from the bus bar to the sensor PCB.

The plots reveal that, as expected, if the PCB distance increases the noise error also increases regardless of device spacing. The amplitude errors in the lower half of the graph show that a device spacing less than 4 mm and 5 mm provide insufficient field strength for the devices to characterize at a PCB distance of 10 mm and 12 mm, respectively.

For the PCB distance of 2 mm (red line in the top half of the plot) as the device spacing increases beyond 10 mm the noise error begins to rise. At these farther spacings the sensors move to a region of mainly vertical field which means they see less signal due to the lack of field seen by the horizontal sensor. When the PCB is farther from the bus bar moving the device spacing to these farther distances (> 12 mm ) is not as much of an issue because the sensors will still be seeing field in both the horizontal and vertical directions.

Figure 6-2 Errors vs Device Spacing