User manual

E-Clip 1 / E-Clip 2 Current Clamps
4
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
R
L
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