METREL A 1018, User Manual

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A 1018, A 1019, A 1033 Current clamps
8
Clamp current transformer must always have a low impedance load on its
secondary side. This loading is realized with an A-meter (for current
sensors with current output). Current clamp with voltage output already
contains the load resistor and its output voltage is proportional to measured
current.
The N1:N2 ratio (primary to secondary winding turns ratio) defines the step-
down current ratio and sensitivity of current clamps. For N2 = 1000 the
sensitivity is defined as
1 mA / 1 A, i.e.: 1 mA of output current is generated from 1 A primary
current for
N1 = 1. The general formula for sensitivity are given below:
2
1
N
N
I I
m S

for current output, and
L m
R
N
N
I U
2
1

for voltage output.
N1 is always integer and means number of passes of conductor carrying
measured current through conductor opening of current clamp.
4.2. Typical applications
Some typical applications of current measurement for standard sensitive
current clamps
(A 1019, A 1033) in combination with appropriate measuring instrument:
-
Harmonic analysis,
-
Measuring electrical power,
-
Measuring current and energy consumption,
-
Functional testing of appliances, machines,
-
Measuring equipment inrush current, etc.
Additional applications related to low current measurements can be
covered with high sensitive type current clamps (A 1018):
-
Measurement of PE leakage current,
-
Measurement of differential current and/or current difference,
-
Contactless measurement of earth resistance,
-
Determining problems in lighting and grounding systems.