OPERATION
4-13
4.5 Current Tracing (non-contact)
NOTE: Disconnect power from the board under test
before using TRACE.
Locating faults using TRACE
This method is effective in the following situations:
• Densely populated double sided PCBs.
• Environmentally coated PCBs.
• Cable looms with internal shorts.
• Shorts on multi-layer boards where the short is on an inner layer.
Use TRACE to detect the current flowing in tracks which cannot be probed using the Needle Probes, e.g.
a track running under an IC or in the middle layer of a multi-layer PCB. When using TRACE the current
must be supplied by the Drive Source leads.
The Drive Source drives a current and the resulting magnetic field is detected using the Current Trace
Probe.
The maximum voltage generated by the Drive Source is 550mV, which will not damage devices or turn on
silicon junctions. Its amplitude can be adjusted using the Drive Source control.
The sensitivity of the Current Trace Probe depends on the orientation of its tip. Minimum sensitivity occurs
when the black lines on the probe tip are either side of the PCB track carrying the current.
Turning the probe through 90°, so that the black lines are directly over the PCB track, gives maximum
sensitivity. This can be observed by the display reading and tone frequency increasing.
Connection and Sensitivity Adjustment
Connect the Drive Source leads across the shorted tracks and turn the Drive Source control fully
clockwise. The most effective way to use TRACE is to connect leads 10–20mm apart on the board under
test. Unless there is a good reason, do not put the leads at opposite corners of the board.
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