METREL A 1018, User Manual

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A 1018, A 1019, A 1033 Current clamps
7
3.2. Cleaning
Use a soft cloth moistened with soapy water or alcohol to clean non-
metallic surface of the current clamps
and leave them to dry totally before
using it.
Notes!

Do not use liquids based on petrol or hydrocarbons!

Do not spill cleaning liquid over the current clamps!
To clean jaw cut surfaces use slightly oiled soft cloth.
3.3. Service and calibration
It is essential that your clamp is regularly calibrated in order to guarantee
the technical specification listed in this User manual. We recommend 2-
year calibration interval.
Metrel encloses an original calibration certificate with every new instrument
and clamp.
For recalibration and repairs under or out of warranty time please contact
your distributor for further information.
4. Current clamp operation
4.1. Substitute electric model for current clamps
Equivalent circuit diagram for current clamp measurement:
Im
Is
I
Clamp
current transformer
Im
RL
Is
U
Clamp
current transformer
a)
b)
N1
N1
N2
N2
Symbols on circuit diagrams have following meaning:
Im Measured (AC) current, primary current
Is Measured current, current transformer secondary current
N1 Number of primary turns - normally N1=1 for current clamps
N2 Number of secondary turns (1000 for all types)
I A-meter
R
L
Measuring resistor
U V-meter