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State of the ARTART Series
Unique, IP67, flexible and thin 1 kV Rogowski coil
• Rated insulation voltage 1 kV CATIII• Accuracy class 0.5 without calibration• 2mm hole to pass security seal
• Electrostatic shieldwww.lemcity.com

Products_sheet_ART_accuracy.indd 1

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23.12.2016 15:42:45

IEC 61869: Class Accuracy
Instrument transformer
LEM FLEXIBLE ART ROGOWSKI COIL FOR MEASURING AC
LEM ART Class 0.5 (IEC 61869-2) is the most accurate coil on the market!
The recently released ART series has improved the transfer ratio accuracy compared with the former series; the tolerance is reduced from1% to 0.5% (class 0.5). A new manufacturing process is used to reduce the centered transfer ratio and the positioning errors. Here below is
an example of statistics on 130 pieces ART B22 D125 batch issued from the new process.
Positioning error

3030

25

25

20

20

Frequency

Frequency

Centered transfer ratio

15
10515
10
5

00
-0.6

-0.4

-0.200.2

Class

0.40

.600.1

0.20.30.40.5ClassAverage 0.2% and maxi 0.4% at 20°C
Example: ART B22 D125
Sample: 130pcs
Target: 0.4%
Average: 0.175%
Min: 0.07%
Max: 0.30%
Xb-3xσ: 0.02%
Xb+3xσ : 0.33%

Class accuracy 0.5% at 20°C
Example: ART B22 D125
Sample: 130pcs
Target: +/- 0.5%
Average: -0.039%
Min: -0.22%
Max: 0.16%
Xb-3xσ: -0.28%
Xb+3xσ : + 0.20%

The LEM ART Rogowski coil has the most accurate manufacturing process on the market!
The ART has an output of 22.5mV/kA @50Hz within 0.5% with measuring load RL=10 kOhms. The LEM manufacturing process of the ART
takes into account the internal resistance in order to guarantee the output accuracy under the rated load. ART is avoiding the use of additional
resistors for the trimming.
Why is the 22.5mV/kA output voltage of the ART so low?
Because the cross section of the coil (ART is the thinnest coil on the market) and the internal resistance RS will remain low. RS is a crucial
point to master the accuracy on absolute value as well as over temperature: the higher the RS, the higher the potential error (provided by theresistive devider RS/RL). Taking into account RS uncertainty (typically 9%) and the very high temperature coefficient of copper (4000ppm/K).
It is a fact that increasing the transfer ratio of Rogowski coils with a higher cross section results in a higher internal coil resistance (Graph 1).
Let’s take the example of a Rogowski coil for which the cross section is increased up to 500mV/kA. The following curves (Graph 2 and 3)
illustrate the impact of RS on the accuracy versus the increasing transfer ratio.
1. Internal resistance RS (W) vs transfer ratio:

2. Potential Output error (%) vs transfer
ratio with load RL = 10kW

3. Temperature coefficient (ppm/K) vstransfer ratio with load RL = 10kW

From 140W @22.5mV to 650W @500mV

From -0.1% @22.5mV to -0.56% @500mV

From -80 ppm/K @22.5mV to -280 ppm/K @500mV0.1

1400-0.1

Output error (%)

1000
800

650
600
400
200
0022.5-0.5-0.56-0.9-1.1

-1.5
500

1000

Transfer ratio mV/kA @ 50Hz-150-200-250- 280-0.7-1.3ARTART-100-0.3

1200

Resistance (Ω)

-50

ART
Temp. coefficient in ppm/K

1600

022.5-300-350-400-450-500

500

1000

Transfer ratio mV/kA @ 50Hz

022.55001000

Transfer ratio mV/kA @ 50Hz

Simulation details: Increasing output to 500mV/kA (15mm cross section, diameter 250mm, 0.1mm wire, fix step winding and 60°C temperature variation)

Products_sheet_ART_accuracy.indd 223.12.2016 15:42:47