8
Another word of caution:
Whenever connecting to a live circuit, remember that the jaws of
a voltage test lead are much wider when they are open than when they are closed. The potential
to short or flash across two adjacent terminals or wires is a constant danger when connecting
to a live circuit. Depending on the current capacity of the circuit being shorted, arc flash and a
deadly explosion of molten material can result!
Once they are securely connected, the deluxe voltage leads are safe for steady voltages of the 600
Vrms rating of ATPOL II. The clamps of the deluxe voltage leads are rated for 1000V working voltage,
measurement category III. This is equivalent to measurement category IV for a working voltage of
600V, the rating of the ATPOL II.
ATP also sells a fused voltage lead set (order DFV). The safety advantage of fused leads is that if a
short occurs through the insulation of a lead to ground, the fuse in the handle should quickly blow out,
preventing the lead from vaporizing in an explosion of molten metal. The safety disadvantage of fused
leads occurs when the fuse is blown or is removed. The user will measure 0 volts on a live circuit and
may be tempted to lower his safety awareness, possibly resulting in shock or damage. The DFV
probes are rated for 1000V, measurement category III.
Current Probes
ATP provides a variety of probes for your use. They offer different measurement ranges, different sizes
and physical characteristics, and the ability to measure different types of current.
Probes such as the AT6001 are excellent choices to use with ATPOL II because they support all the
accuracy specifications of the product. For instance, the AT6001 has an accuracy of 0.5% whereas
many probes on the market have an accuracy of 2-3%. Also, the AT6001 maintains its accuracy for
frequencies up to 20,000 Hz. With our spectrum analyzer option (order FAO) it can be used to
measure frequencies up to 100,000 Hz riding on the power line. This allows accurate current and
power readings of distorted waveforms, accurate readings of harmonics, and the measurement of
current transients that other probes would not even detect.
Phase shift is also an important probe characteristic. The AT6001 has less than 1/2 degree of phase
shift across the frequency range when measuring currents above 50 amps and just 1.5 degrees at 5
amps. This means that instantaneous measurements of power are highly accurate, regardless of the
waveform shape. The phase shift characteristics of most other probes on the market are not this good.
This results in erroneous power and cost measurements and distorted waveforms. Please Note: To
diminish phase shift when measuring small currents, it is advisable to clamp onto multiple "turns" of the
same conductor in order to increase the effective current being sensed.
The AT6003 offers two advantages over the AT6001, but these advantages come at a cost. Its
advantages are that the AT6003 is a very small size (5.25
2.00
1.35 inches) and second, it offers
much greater sensitivity since it reads currents from 20 milliamps to 5 amps (as compared to the
AT6001 measuring 1 - 1,000 amps). The tradeoff is accuracy. The probe has a basic accuracy of 2%
and its phase shift varies by frequency and by amplitude. All told, you can expect to measure current to
a nominal 2.25% accuracy and power and cost to a nominal 3% accuracy using the AT6003 probe.
The AT6002 probe is the same compact size as the AT6003. The AT6002 measures from 0.1 to 100
amps at 2% accuracy. It is a good choice over the AT6001 if you wish to lock ATPOL II, its leads, and
current probes inside a power panel that you are monitoring. It is also a good choice when small size is
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