Troubleshooting Basics 39

Step 1. Release the pointer lock. Step 2. Turn the selector knob until the highest current range appears in the scale window. Step 3. Press the trigger to open the jaws of the clamp and place them around a single conductor.

Step 4. Release finger pressure on the trigger slowly, keeping an eye on the scale while the jaws close around the conductor. If the pointer jumps abruptly to the upper range of the scale before the jaws are completely closed, the current is too high for the scale selected. Immediately remove the jaws from around the conductor, and use a higher scale.

Never encircle two or more conductors; only encircle one conductor as shown in Figure 1-1. If the pointer moves normally, close the jaws completely and read the current in amperes indicated on the scale.

Accuracy

When using clamp-on ammeters, follow these precautions to obtain accurate readings: 1. Be certain the frequency of the conductor being tested is within the range of the instrument. Most ammeters are calibrated at 70 Hz. 2. Magnetic fields can affect current readings.

To minimize this problem, try to avoid using

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