METREL A 1281 User manual

Multi range AC current clamps
(1000A / 100A / 5A / 0.5A)
A 1281
Instruction manual
Version 2.1, Code no. 20 751 696

Distributor:
Manufacturer:
METREL d.d.
Ljubljanska cesta 77
1354 Horjul
Slovenia
web site: http://www.metrel.si
e-mail: [email protected]
© 2014 METREL
Mark on your equipment certifies that this equipment meets the requirements of the EU
(European Union) concerning safety and electromagnetic compatibility regulations.
No part of this publication may be reproduced or utilized in any form or by any means without
permission in writing from METREL.

A 1281 Multi range AC current clamps
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Table of contents
DESCRIPTION OF CURRENT CLAMPS........................................................................5
CURRENT CLAMPS OPERATION.................................................................................6
OPERATION INSTRUCTIONS..............................................................................................6
SUBSTITUTE ELECTRIC MODEL FOR CURRENT CLAMPS .....................................................7
TYPICAL APPLICATIONS..............................................................................................7
POWER QUALITY MEASUREMENT.....................................................................................7
POWER MEASUREMENT ..................................................................................................8
LEAKAGE CURRENT MEASUREMENT.................................................................................8
Measurement of Leakage Current by Direct Method..............................................................8
Measurement of Differential Current and/or Current Difference...........................................8
Determining Problems in Lighting and Grounding Systems...................................................9
MAINTENANCE..............................................................................................................9
INSPECTION ...................................................................................................................9
CLEANING......................................................................................................................9
SERVICE AND CALIBRATION .............................................................................................9
TECHNICAL SPECIFICATIONS...................................................................................10
GENERAL.....................................................................................................................10
ACCURACY AND PHASE ERROR .....................................................................................11
TYPICAL PERFORMANCE CHARACTERISTICS ...................................................................11
ELECTROMAGNETIC COMPATIBILITY (EMC) ....................................................................12

A 1281 Multi range AC current clamps
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Symbols and Warnings
To ensure a high level of operator's safety during using of A 1281 Multi range AC current
clamps the following warnings has to be considered:

!
Do not use the current clamp if any damage is noticed!

!
Consider all generally known precautions in order to avoid risk of electric shock
while dealing with electric installations!

!
Do not extend hands over safety barrier to prevent of electric shock! Only
handles are allowed to be touched during measurement!

!
Symbol on the current clamp indicates the possibility of a hazardous live
condition if the operator ignores the required safety measures.

!
If the current clamps are used in a manner not specified in this User manual, the
provided protection can be impaired!

!
Only a competent, authorized person is allowed to carry out service intervention!

!
Do not connect clamp output elsewhere than to Metrel Power Quality Analyzer’s!
Symbol on the current clamp indicates the possibility to use the current clamp on
non-insulated conductors.
Current clamps are protected by double insulation.

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Description of current clamps
The A 1281 multi range current clamps are designed for measuring alternating currents on low
and medium power installations: 50 mA ÷ 1000 A.
They have electronic module, and can be connected only to Metrel Power Quality Analysers’,
series:
PowerQ (MI 2492)
PowerQPlus (MI 2392)
PowerQ4 (MI 2592)
PowerQ4 Plus (MI 2792)
Energy Master (MI 2883)
Power Q4 (MI 2885)
Power Master (MI 2892)
Power Master XT (MI 2893)
Clamps have four current ranges 0.5A, 5A, 100A and 1000A, which are selected directly by the
connected instrument. Embedded electronic module is powered directly from the connected
instrument and does not need any additional power supply.
The current transducer is housed in a plastic case that maintains double insulation as defined in
Main parts of the current clamps are shown on figure bellow:
1
2
3
4
5
1. handles,
2. safety barrier,
3. conductor opening,
4. clamps jaw,
5. cable connection with
connector.
Figure 1: Multi range AC current clamps

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Current clamps operation
Operation Instructions
Figure 2: Current clamps A 1281 - connection to the measuring instrument
Step 1
Connect A 1281 current clamps output connector to the appropriate (Metrel Power Quality
Analyzer) measuring instrument’s current input terminal. (See figure 2)
!
Do not connect clamp output elsewhere than to Metrel Power Quality Analyzers’
series of measuring instruments!
Step 2
Switch on the measuring instrument. Set Smart clamps and range on instrument’s measuring
setup. (For further information see Instruction manual of measuring instrument.)
Step 3
Clamp the probe around the current-carrying conductor(s) to be measured. Make sure that
probe jaws are tightly closed around the conductor(s).
!
Do not extend hands over safety barrier to prevent of electric shock! Only handles
are allowed to be touched during measurement!
!
Do not use the current clamp if any damage is noticed!
!
Consider all generally known precautions in order to avoid risk of electric shock
while dealing with electric installations!
Step 4
Make measurement. (For further information see Instruction manual of measuring instrument.)

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Step 5
Disconnect clamps from the conductor(s). Use all safety measures as described in step 3.
Substitute Electric Model for Current Clamps
Equivalent circuit diagram for current clamp measurement:
Im Is
1 : N2
I
U
Range selection:
- 500mA
- 5 A
- 100A
- 1000A
GND
U(I)
Instrument
Connector
Figure 3: Current clamps A 1281 - block diagram
Symbols on circuit diagrams have following meaning:
Im
Measured (AC) current, primary current
Is
Measured current, current transformer secondary current
N2
Number of secondary turns (N2 = 1000)
U(I)
Output voltage as function of current U = k * Im. Factor k depends on
selected current range as shown in table bellow:
Range (A)
k (V/A)
0,5
2
5
0,2
100
0,01
1000
0,001
Typical applications
Power Quality Measurement
A 1281 current clamps have linear response through wide frequency bandwidth (see Figure 8).
Therefore, they are well suited for:
Power Quality auditing,
EN 50160 or troubleshooting. Particularly for:
Current distortion measurement
Inrush measurement
Functional testing of appliances, machines, etc.
High precision (see Figure 6) and wide measurement range can cover most of practical LV
current measurements.

A 1281 Multi range AC current clamps
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Power Measurement
A 1281 current clamps have small phase shift (see Figure 7 and Figure 9) over wide frequency
range. Therefore, they are well suited for:
Power and energy measurements (active, reactive, apparent)
Power factor measurements
Power/Energy efficiency
Leakage Current Measurement
Measurement of Leakage Current by Direct Method
This method is used when measuring the current through one (embraced) conductor.
Figure 4: Leakage current measurement –direct method
Measurement of Differential Current and/or Current Difference
The differential method sums the current passing through two or more active (embraced)
conductors. If no current is leaking to earth, the sum of the currents passing through active
conductors must be exactly zero regardless of the load currents. If a leakage current is flowing
to earth, it must be equal to the difference in current between the conductors contained in the
current clamp (although, if alternative earth paths exist, this may not be equal to the current
passing through the PE conductor).
Note
Note that the direction of currents in the conductors must be considered if the differential
method is used.
Figure 5: Leakage current measurement –differential method

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Determining Problems in Lighting and Grounding Systems.
Faults in electrical installations and equipment can cause additional continuous or short-
lasting leakage currents. Typical faults that can cause increased leakage currents are:
Deterioration of insulation (because of pollution, moisture, corrosion). This is causing
a gradual increase of the resistive leakage current.
Faults in electronic equipment.
If the neutral and PE wiring are connected together anywhere in the installation this
can result in an improper current distribution through the neutral and PE conductors.
Note
Metrel Application note: Measuring of leakage current contain many practical aspects and
examples of leakage current measurement.
Maintenance
Inspection
To maintain operator safety and ensure reliability of the current clamp it is good practice to
inspect it on a regular basis. Check that the enclosure and optional connection are without
defects such as scratches or breaks.
Jaw surface must be clean. Pollution on jaw surfaces reduces the current clamp sensitivity.
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.
!
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.
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.
!
Only a competent, authorized person is allowed to carry out service intervention!

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Technical Specifications
General
Safety specification
Over voltage category: 600 V CAT III,
Pollution degree: 2
Double insulation
Environment conditions
Working temperature: -20 0C ÷ 55 0C
Storage temperature: -30 0C ÷ 70 0C
Temperature dependency (Note 1):
+/- 0.02 % of reading / °C
Humidity: 0 % ÷ 85 %,
Linearly decreasing for T > 35 0C
Altitude: 2000 m
Applied standards
Safety: EN/IEC 61010-1
EN/IEC 61010-2-32
EMC: EN/IEC 61326-1
Mechanical data
Jaw opening: 52 mm
Maximum conductor sizes:
Cable: < 50 mm
Bar: 1 bar 50 mm x 5 mm,
4 bars 30 mm x 5 mm
Housing flammability: UL94 –V-1
Dimension: 220 mm x 120 mm x 48 mm
Weight: 600 g
Note 1: No additional error in range 15 ºC – 25ºC,
for higher temperatures: Temp. error = (Temp - 25ºC) * Temperature dependency
for lower temperatures: Temp. error = (15ºC - Temp) * Temperature dependency

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Accuracy and Phase Error
Reference conditions:
Temperature: 23 0C 1 0C
Humidity: 60 %
Current range
Nominal current (INom)
0.5 A
5 A
100 A
1000 A
Current ratio
0.5 A/V
5 A/V
100 A/V
1000 A/V
Peak current
1.5 APEAK
15 APEAK
246 APEAK
1700 APEAK
Crest factor @ Nominal current
3,0
3,0
2,46
1,7
Accuracy
Current range*
50 mA ÷1 A
0.5 A ÷10 A
10 A ÷175 A
100 A ÷1200 A
RMS Current Accuracy
0.5 % of m.v.
0.5 % of m.v.
0.5 % of m.v.
0.5 % of m.v.
Frequency range
40 Hz ÷ 700 Hz (<0.50phase error)
700 Hz ÷ 2500 Hz (<30phase error)
Continuity of measurements
1000 A continuous
1200 A (40 min / 20 min intermitted)
Load impedance
< 1 kΩ
Working voltage
600 Vrms
Influence of neighbour conductor:
< 1 mA/A at 50 Hz
Influence of conductor position:
< 0.3 % at f < 400 Hz
*Accuracy for 0÷10% range is 0.1% ·INom
m.v. –measured value
Typical Performance Characteristics
-2,00
-1,50
-1,00
-0,50
0,00
0,50
0,0 2,0 4,0 6,0 8,0 10,0 12,0
Current (A)
Accuracy (%)
Figure 6: Accuracy vs. current (for 5A range)
0,00
0,20
0,40
0,60
0,80
1,00
1,20
1,40
0 5 10 15
Current (A)
Phase Error (°)
Figure 7: Phase error vs. current (for 5A range)

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0,00
0,50
1,00
1,50
2,00
2,50
10 100 1000 10000
Freqency (Hz)
Acurracy (%)
Figure 8: Accuracy vs. frequency (for 5A range)
0,0
0,5
1,0
1,5
2,0
2,5
3,0
10 100 1000 10000
Freqency (Hz)
Phase Error (°)
Figure 9: Phase error vs. frequency (for 5A range)
Electromagnetic Compatibility (EMC)
Current clamps A 1281 conforms to the directive 2004/108/EC for EMC, as defined by
EN-61326-1:
- Emission: Class B (domestic and industrial use).
- Immunity: Intended for use in industrial locations, but can also be used for
domestic purposes (Performance criteria B), with addition to the tables bellow:
Table 1: Immunity to radiated RF fields*
Range
Operational conditions
Disturbance < 0,2 %
Disturbance > 0,2 %
0.5A
0.05 A ÷ 0.5 A
322 MHz ÷ 1 GHz
80MHz ÷ 322 MHz
5A
0.5 A ÷ 5 A
250 MHz ÷ 1 GHz
80MHz ÷ 250 MHz
100A
10 A ÷ 100 A
80 MHz ÷ 1 GHz
–
1000A
100 A ÷ 1000 A
80 MHz ÷ 1 GHz
–
* Field strength: 10V/m, Modulation: AM, 80%, 1 kHz
Table 2: Immunity to Magnetic field*
Range
Operational conditions
Disturbance
0.5A
0.05 A ÷ 0.5 A
< 6 % of m.v.
5A
0.5 A ÷ 5A
< 0.5 % of m.v.
100A
10 A ÷ 100 A
< 0.2 % of m.v.
1000A
100 A ÷ 1000 A
< 0.2 % of m.v.
*Field strength: 30 A/m, Modulation: AM, 80%, 1kH.
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