ACDC-620T Amprobe, ACDC-620T Datasheet - Page 52

• Manufacturer Part Number: ACDC-620T
• Description: DMM CLAMP-ON TRMS
• Manufacturer: Amprobe
• Type: Digital (DMM)r

Specifications of ACDC-620T

• Includes: Battery, Case, Test Leads
• Style: Clamp
• Display Digits: 4
• Display Type: LCD, Bar Graph
• Display Count: 4000
• Function: Voltage, Current, Resistance, Capacitance, Temperature
• Functions, Extra: Continuity, Diode Test
• Features: Auto Off, Hold, Min/Max/Ave, Sleep
• Ranging: Auto/Manual
• Response: True RMS
• Frequency: 45 Hz to 65 Hz
• Maximum Ac Current: 1 KA
• True Rms: Yes
• Voltage: 400 V/100 V
• Lead Free Status / RoHS Status: Contains lead / RoHS compliant by exemption
• Other names: 2730822

CURRENT HARMONICS THEORY
True-RMS current is very important because it directly relates to the amount of
heat dissipated in wiring, transformers, and loads. Most clamp-on meters
already in the field measure average current, not true RMS current, even if
this average value is displayed on a scale calibrated in RMS. These average-
sensing meters are accurate only for sinusoidal signals.
All current signals are distorted in some way. The most common is harmonic
distortion caused by non-linear loads such as office machines, medical equip-
ment, personal computers, or speed controls for motors. Harmonic distortion
causes significant currents at frequencies that are odd multiples of the power
line frequency. Harmonic current can cause a substantial load on the neutral
wires of wye-connected power distribution systems.
In most countries, 50Hz or 60Hz power distribution systems include 3-phase
delta primary - wye secondary transformers. The secondary generally pro-
vides 120V AC from phase to neutral, and 208V AC from phase to phase.
Historically, balancing the loads on each phase was a big headache for the
electrical system designer.
Typically, the vector addition of the phase currents in the transformers' neutral
wire is zero or quite low in a wellbalanced system. Typical devices that pres-
ent linear loading include incandescent lighting and small motors. The result is
essentially a sine wave current in each phase and a low neutral current at a
frequency of 5OHz: or 60Hz.
Devices such as TV sets, fluorescent lighting, video machines, and microwave
ovens are now commonly drawing power line current for only a fraction of
each cycle so that they cause non-linear loading and subsequent
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