Clamp meters rely on magnetic induction to measure AC current non-contact. A current flowing through a wire produces a fluctuating magnetic field proportional to the current. A current transformer inside the clamp meter senses these magnetic fluctuations and converts it to an AC current reading. Clamp meters operate using a current transformer (CT) to pick up the magnetic flux generated by a current flowing through a conductor. The CT induces a proportional current on the secondary side which is measured and displayed digitally. Safety precautions for using clamp testers include not measuring current with probes inserted, setting the correct range, checking battery condition, and avoiding dropping the tester.

3. PARTS
OF
A
CLAMP
TESTER

4. Clamp meters rely on the principle of magnetic
induction to make non-contact AC current
measurements. Electric current flowing through
a wire produces a magnetic field. Since
alternating current frequently reverses polarity,
it causes dynamic fluctuations in the magnetic
field which are proportional to the current flow.
A current transformer inside the clamp meter
senses the magnetic fluctuations and converts
the value to an AC current reading. This type of
measurement is convenient for measuring very
high AC currents.

5. How Do Clamp Meters Operate?
In general AC clamp meters operate on the
principle of current transformer(CT) used to pick
up magnetic flux generated as a result of current
flowing through a conductor. Assuming a current
flowing through a conductor to be the primary
current, you can obtain a current proportional to
the primary current by electromagnetic induction
from the secondary side(winding) of the
transformer which is connected to a measuring
circuit of the instrument. This permits you to take
an AC current reading on the digital display(in the
case of digital clamp meters) as illustrated by the
block diagram.

6. SAFETY PRECAUTION IN USING CLAMP TESTER
Never measure current while the test probes are
inserted into the input jacks.
Be sure that the tester is set to the correct range setting
Always check the condition of its battery. Worn out
batteries will damage the internal setting of the tester.
Do not drop the tester