(Analyze) Current Measurement vs. Current Flow

We’re going to do a conductive locate using 4 kHz, and the output is 35 mA. At our transmitter, our signal is going to be able to go to the earth, to the cable in an easterly direction, and the cable in a westerly direction, as well as the service drop to the building (Figure 1). Here is our transmitter location (Figure 2).

We’re going to look at the current measurement reading of 4.94 mA and the digital depth of 1’11” (Figure 3). We’re going to take the far-end ground off of the cable that we’re locating (Figure 4). Watch the milliamps, and watch the signal strength. Both are significantly reduced by removing the cable’s far-end ground, but the digital depth does not change (Figure 5).

Current measurement (mA) is raw signal strength factored by depth. If depth is constant, but raw signal strength drops, current measurement must also drop. Raw signal strength is not affected by gain. Here, our signal strength is 73.2, and our current measurement reading on the receiver is 114 mA. We’re going to reduce the gain, and we know that will reduce the signal strength. What will it do to the current measurement reading? Nothing. Current measurement and the digital depth stay exactly the same, even though gain was reduced. Only the peak reading changes (Figure 6). 

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