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Application Note
CS5480/84/90 Measurement Accuracy
vs. IEC Standards
1. Introduction
Cirrus Logic’s CS5480, CS5484, and CS5490 energy measurement ICs benefit from on-chip, high-performance, 24bit ADC converters in conjunction with its digital calibration and compensation algorithms. This application note presents accuracy results from testing the CS5480. The CS5484 and CS5490 uses the same core technology as the
CS5480. Testing results of the CS5484 and CS5490 show nearly identical results.
The CS5480 has world-leading accuracy over an extensive, dynamic range. This application note cites measurements of active energy, reactive energy, and IRMS load performance acquired from the CS5480 using three different
types of current sensor: Rogowski coil, current transformer (CT), and shunt. A comparison between the CS5480
measurements and the IEC 62053 standards is presented. This comparison shows that the CS5480 meets IEC
62053-22 class 0,2S standards for active energy and IEC 62053-23 class 2 standards for reactive energy. Comparison with the ANSI C12.20 standard is not included in this application note because the ANSI standard is less stringent than the IEC 62053 standard, so it is implied that the CS5480 meets it.
2. Test Setup
The following diagram illustrates the connections between the PPS400.3 power source, PRS400.3 power reference,
current sensor, CDB5480U board (+3.3V DC power supply), and a host PC.
+3.3V DC Power Supply
+3.3V
PC
GND
VIN 1+
J4
N3
RS232
U3
422K
422K
422K
422K
Un
RX
1K
M
C
U
USB
CDB5480U GUI
GND
27n
Power Source
VIN 1-
CS5480
PPS400.3
J1
I3
RS232
TX
27n
LINE 1
U3
Ib
V+
Current
Sensor
IIN1-
GND
GND
V-
IIN1+
100
27n
27n
27n
N3
100
Power Reference
IIN1-
1K
27n
1K
CAMCAL®
for
WINDOWS
DO1
IIN1+
PRS400.3
SH2003
I3
CDB5480U
METER
Energy Pulses
Figure 1. Test Setup Connection Diagram
Cirrus Logic, Inc.
http://www.cirrus.com
Copyright Cirrus Logic, Inc. 2012
(All Rights Reserved)
MAR’12
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The Cirrus Logic CDB5480U demonstration board and current sensor form a single-phase, two-wire energy meter.
The CDB5480U software is installed on a host PC and used to configure, calibrate, and control the meter using the
USB port. The software collects the measurement results from the CS5480 registers once per second. CAMCAL®
for WINDOWS software controls the MTE Meter Test Equipment AG PPS400.3 power source and PRS400.3 power
reference using two COM ports. CAMCAL performs the active and reactive accuracy test procedure automatically.
The active or reactive energy pulses provided by the CS5480 drive the on-board LED using energy pulse output
DO1. The energy pulses are sensed by photoelectric scanning head SH2003 and directed back into PRS400.3. The
accuracy of the active and reactive energy is then measured by PRS400.3 and sent to the CAMCAL software. The
meter constant is 2000 impulses/kWh, or 2000 impulses/kVarh.
IRMS accuracy is manually calculated and based on a 10-second average using the IRMS register values. The IRMS
register is read once per second using the CDB5480U software.
2.1 Calibrations and Meter Types
Prior to the accuracy test, the following calibrations and compensations were performed:
•
Gain calibration
•
AC offset calibration
•
Phase compensation
•
Active and reactive power offset correction
Using the CDB5480U board with different current sensors forms different types of meters. To test the accuracy of
the CS5480, the following meters were formed:
•
Rogowski coil meter, where Un = 240V and Ib(max) = 2 (80A) at 50Hz
•
Current transformer (CT) meter, where Un = 240V and Ib(max) = 2.5 (100A) at 50Hz
•
Shunt meter, where Un = 240V and Ib(max) = 2.5 (100A) at 50Hz
All accuracy tests were conducted at room temperature. Influences from ambient temperature and self-heating are
not included.
Refer to Application Note 366, entitled CS5480/84/90 Power Meter Calibration, for more information about calibrations and compensations.
Refer to the CDB5480U data sheet, entitled CDB5480U Engineering Board and GUI Software, for more information
about the CDB5480U board.
Refer to the CS5480 data sheet, entitled Three Channel Energy Measurement IC, for more information about the
CS5480.
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3. Accuracy Test with Rogowski Coil, Un = 240V and Ib(max) = 2(80A) at 50Hz
Pulse PA3202NL is used as the current sensor. The secondary output voltage of PA3203NL is 416μV/A at
50Hz. When the meter is applied with the maximum load current, Imax = 80A, the Rogowski coil secondary output is approximately 33mVRMS, which is below the CS5480 maximum I-channel input range when setting the
PGA for current channel 1 (I1) to 50x.
High-pass filter (HPF) is enabled on the voltage channel: V1FLT[1:0] = ‘01’
Integrator is enabled on the current channel: I1FLT[1:0] = ‘11’
IIN 1100Ω
1KΩ
J1
Current
27nF
IIN1-
27nF
V+
Rogowski Coil
PA3202 NL
GND
GND
CS5480
VIIN1+
27nF
100Ω
27nF
1KΩ
IIN 1+
Figure 2. Connection between Rogowski Coil and CS5480
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3.1 Accuracy Results for Active Energy Load Performance
0.6
Note: CS5480, where Un = 240 V, Ib(max) = 2 (80 A) at 50 Hz
Percent Error (%)
0.4
0.2
0
IEC 62053-22 Class 0,2S Spec, PF = 1
-0.2
IEC 62053-22 Class 0,2S Spec, Lagging PF = 0.5 or Leading PF = 0.8
-0.4
-0.6
0.01
0.1
PF = 1
Lagging PF = 0.5
1
Load Current (A)
10
100
Leading PF = 0.5
Figure 3. Active Energy Load Performance vs. IEC 62053-22 Class 0,2S Standard
Power Factor
PF = 1
Lagging PF = 0.5
Leading PF = 0.5
Load Current (A)
80
8
0.8
0.16
0.08
0.04
0.03
0.02
80
8
0.8
0.16
0.08
0.04
80
8
0.8
0.16
0.08
0.04
Current Dynamic Range (x:1)
1
10
100
500
1000
2000
3333
4000
1
10
100
500
1000
2000
1
10
100
500
1000
2000
Error
0.04%
0.04%
0.04%
0.04%
0.07%
0.05%
0.06%
0.02%
0.05%
0.05%
0.04%
0.06%
0.05%
0.06%
0.04%
0.04%
0.05%
0.04%
0.05%
0.07%
Table 1. Active Energy Load Performance
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3.2 Accuracy Results for Reactive Energy Load Performance
3
Note: CS5480, where Un = 240 V, Ib(max) = 2 (80 A) at 50 Hz
Percent Error (%)
2
1
0
-1
IEC 62053-23 Class 2 Spec, sinࢥ = 1
-2
IEC 62053-23 Class 2 Spec, sinࢥ = 0.5
-3
0.01
0.1
1
10
100
Load Current (A)
sin ࢥ = 1
Lagging sin ࢥ = 0.5
Leading sin ࢥ = 0.5
Figure 4. Reactive Energy Load Performance vs IEC 62053-23 Class 2 Standard
Power Factor
sin = 1
Lagging sin = 0.5
Leading sin = 0.5
Load Current (A)
80
8
0.8
0.16
0.08
0.04
0.03
0.02
80
8
0.8
0.16
0.08
0.04
80
8
0.8
0.16
0.08
0.04
Current Dynamic Range (x:1)
1
10
100
500
1000
2000
3333
4000
1
10
100
500
1000
2000
1
10
100
500
1000
2000
Error
0.00%
0.01%
0.01%
-0.02%
-0.02%
-0.01%
0.00%
-0.03%
0.23%
0.24%
0.17%
0.21%
0.16%
0.22%
-0.20%
-0.20%
-0.26%
-0.23%
-0.25%
-0.24%
Table 2. Reactive Energy Load Performance
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3.3 Accuracy Results for IRMS Load Current Performance
0.3
Note: CS5480, where Un = 240 V, Ib(max) = 2 (80 A) at 50 Hz
Percent Error (%)
0.2
0.1
0
-0.1
-0.2
-0.3
0.1
1
10
100
Load Current (A)
Figure 5. IRMS Load Current Performance
Load Current (A)
80
8
0.8
0.16
0.08
Current Dynamic
Range (x:1)
1
10
100
500
1000
IRMS Register Value
(10-Second Average)
0.60011034
0.06009873
0.006001252
0.001200491
0.000600857
IRMS Error
0.02%
0.02%
0.02%
0.04%
0.14%
Table 3. IRMS Load Current Performance
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4. Accuracy Test with Current Transformer CT, Un = 240V and Ib(max) = 2.5(100A) at 50Hz
Taehwatrans TZ76V is used as the current sensor. The CT has the turn's ratio of 2500:1. Use 4Ω as the load
resistor. When the meter is applied with the maximum load current, Imax = 100A, the secondary output voltage
is (100/2500) × 4 = 0.16 VRMS, which is below the maximum I-channel input range when setting the PGA for
current channel 1 (I1) to 10x.
High-pass filter (HPF) is enabled on the voltage channel: V1FLT[1:0] = ‘01’
High-pass filter (HPF) is enabled on the current channel: I1FLT[1:0] = ‘01’
IIN 1-
1KΩ
J1
Current
27nF
1KΩ
IIN1-
V+
CT
TZ76V
CS5480
4Ω
VIIN1+
27nF
1KΩ
IIN 1+
1KΩ
Figure 6. Connection between Current Transformer CT and CS5480
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4.1 Accuracy Results for Active Energy Load Performance
0.6
Note: CS5480, where Un = 240 V, Ib(max) = 2.5 (100 A) at 50 Hz
Percent Error (%)
0.4
0.2
0
IEC 62053-22 Class 0,2S Spec, PF = 1
-0.2
IEC 62053-22 Class 0,2S Spec, Lagging PF = 0.5 or Leading PF = 0.8
-0.4
-0.6
0.01
0.1
1
10
100
Load Current (A)
PF = 1
Lagging PF = 0.5
Leading PF = 0.5
Figure 7. Active Energy Load Performance vs IEC 62053-22 Class 0,2S Standard
Power Factor
PF = 1
Lagging PF = 0.5
Leading PF = 0.5
Load Current (A)
100
10
1
0.2
0.1
0.05
0.03
0.025
100
10
1
0.2
0.1
0.05
100
10
1
0.2
0.1
0.05
Current Dynamic Range (x:1)
1
10
100
500
1000
2000
3333
4000
1
10
100
500
1000
2000
1
10
100
500
1000
2000
Error
0.04%
0.03%
0.04%
0.03%
0.04%
0.01%
0.03%
0.09%
-0.02%
0.07%
0.11%
0.11%
0.09%
0.05%
0.08%
0.00%
-0.04%
-0.08%
-0.14%
-0.14%
Table 4. Active Energy Load Performance
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4.2 Accuracy Results for Reactive Energy Load Performance
3
Note: CS5480, where Un = 240 V, max = 2.5 (100 A) at 50 Hz
Percent Error (%)
2
1
0
-1
IEC 62053-23 Class 2 Spec, sinࢥ = 1
-2
IEC 62053-23 Class 2 Spec, sinࢥ = 0.5
-3
0.01
0.1
1
10
100
Load Current (A)
sin ࢥ = 1
Lagging sin ࢥ = 0.5
Leading sin ࢥ = 0.5
Figure 8. Reactive Energy Load Performance vs IEC 62053-23 Class 2 Standard
Power Factor
sin = 1
Lagging sin = 0.5
Leading sin = 0.5
Load Current (A)
100
10
1
0.2
0.1
0.05
0.03
0.025
100
10
1
0.2
0.1
0.05
100
10
1
0.2
0.1
0.05
Current Dynamic Range (x:1)
1
10
100
500
1000
2000
3333
4000
1
10
100
500
1000
2000
1
10
100
500
1000
2000
Error
-0.05%
-0.03%
-0.01%
-0.03%
-0.02%
-0.06%
-0.06%
-0.07%
0.28%
0.16%
0.11%
0.09%
0.06%
-0.08%
-0.29%
-0.21%
-0.15%
-0.16%
-0.16%
-0.32%
Table 5. Reactive Energy Load Performance
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4.3 Accuracy Results for IRMS Load Current Performance
0.3
Note: CS5480, where Un = 240 V, Ib(max) = 2.5 (100 A) at 50 Hz
0.2
Percent Error (%)
0.1
0
-0.1
-0.2
-0.3
0.01
0.1
1
10
100
Load Current (A)
Figure 9. IRMS Load Current Performance
Load Current (A)
100
10
1
0.2
0.1
0.05
0.03
Current Dynamic
Range (x:1)
1
10
100
500
1000
2000
3333
IRMS Register Value
(10-Second Average)
0.59990938
0.059996352
0.00600099
0.001200253
0.000600082
0.000300026
0.00018006
IRMS Error
-0.02%
-0.01%
0.02%
0.02%
0.01%
0.01%
0.03%
Table 6. IRMS Load Current Performance
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5. Accuracy Test with Shunt, Un = 240V and Ib(max) = 2.5(100A) at 50Hz
A 100μΩ shunt is used as the current sensor. When the meter is applied with the maximum load current,
Imax = 100A, the voltage output from the shunt is 10mVRMS, which is below the maximum I-channel input range
when setting the PGA for current channel 1 (I1) to 50x.
High-pass filter (HPF) is enabled on the voltage channel: V1FLT[1:0] = ‘01’
High-pass filter (HPF) is enabled on the current channel: I1FLT[1:0] = ‘01’
IIN 1-
1KΩ
J1
Current
Shunt
100μΩ
27nF
IIN1-
V+
CS5480
VIIN1+
27nF
IIN 1+
1KΩ
Figure 10. Connection between Shunt and CS5480
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5.1 Accuracy Results for Active Energy Load Performance
0.6
Note: CS5480, where Un = 240 V, Ib(max) = 2.5 (100 A) at 50 Hz
0.4
Percent Error (%)
0.2
0
IEC 62053-22 Class 0,2S Spec, PF = 1
-0.2
IEC 62053-22 Class 0,2S Spec, Lagging PF = 0.5 or Leading PF = 0.8
-0.4
-0.6
0.01
0.1
1
10
100
Load Current (A)
PF = 1
Lagging PF = 0.5
Leading PF = 0.5
Figure 11. Active Energy Load Performance vs IEC 62053-22 Class 0,2S Standard
Power Factor
PF = 1
Lagging PF = 0.5
Leading PF = 0.5
Load Current (A)
100
10
1
0.2
0.1
0.05
0.03
0.025
100
10
1
0.2
0.1
0.05
100
10
1
0.2
0.1
0.05
Current Dynamic Range (x:1)
1
10
100
500
1000
2000
3333
4000
1
10
100
500
1000
2000
1
10
100
500
1000
2000
Error
0.02%
0.01%
0.02%
0.00%
0.06%
0.06%
0.05%
0.03%
-0.02%
0.02%
0.02%
-0.03%
-0.02%
0.04%
-0.01%
0.01%
-0.04%
-0.09%
-0.03%
0.04%
Table 7. Active Energy Load Performance
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3
Note: CS5480, where Un = 240 V, Ib(max) = 2.5 (100 A) at 50 Hz
2
Percent Error (%)
1
0
-1
IEC 62053-23 Class 2 Spec, sinࢥ = 1
-2
IEC 62053-23 Class 2 Spec, sinࢥ = 0.5
-3
0.01
0.1
1
10
100
Load Current (A)
sin ࢥ = 1
Lagging sin ࢥ = 0.5
Leading sin ࢥ = 0.5
Figure 12. Reactive Energy Load Performance vs IEC 62053-23 Class 2 Standard
Power Factor
sin = 1
Lagging sin = 0.5
Leading sin = 0.5
Load Current (A)
100
10
1
0.2
0.1
0.05
0.03
0.025
100
10
1
0.2
0.1
0.05
100
10
1
0.2
0.1
0.05
Current Dynamic Range (x:1)
1
10
100
500
1000
2000
3333
4000
1
10
100
500
1000
2000
1
10
100
500
1000
2000
Error
-0.01%
-0.01%
-0.02%
-0.05%
0.02%
0.06%
0.06%
0.03%
0.20%
0.17%
0.19%
0.09%
0.11%
0.05%
-0.22%
-0.20%
-0.23%
-0.26%
-0.27%
-0.35%
Table 8. Reactive Energy Load Performance
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5.2 Accuracy Results for IRMS Load Current Performance
0.30
Note: CS5480, where Un = 240 V, Ib(max) = 2.5 (100 A) at 50 Hz
Percent Error (%)
0.20
0.10
0.00
-0.10
-0.20
-0.30
0.1
1
10
100
Load Current (A)
Figure 13. IRMS Load Current Performance
Load Current (A)
100
10
1
0.2
0.1
Current Dynamic
Range (x:1)
1
10
100
500
1000
IRMS Register Value
(10-Second Average)
0.599839375
0.059990012
0.00599035
0.001199412
0.000599265
IRMS Error
-0.03%
-0.02%
-0.02%
-0.05%
-0.12%
Table 9. IRMS Load Current Performance
6. Summary
The CS5480 supports three current sensors: Rogowski coil, current transformer, and shunt. It achieves 0.1% accuracy over 4000:1 dynamic range at PF = 1 for active energy and sin ϕ = 1 for reactive energy. The active and reactive
energy load performance exceeds IEC 62053-22 class 0,2S specifications and IEC 62053-23 class 2 specifications,
respectively. The CS5480 is the best-in-class analog front-end device for high-accuracy electricity meters with extensive load range: Imax / Ib ≥ 40.
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7. Revision History
Revision
Date
REV1
MAR 2012
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Changes
Initial Release.
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Contacting Cirrus Logic Support
For all product questions and inquiries contact a Cirrus Logic Sales Representative.
To find one nearest you go to http://www.cirrus.com
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Cirrus Logic, Inc. and its subsidiaries ("Cirrus") believe that the information contained in this document is accurate and reliable. However, the information is subject
to change without notice and is provided "AS IS" without warranty of any kind (express or implied). Customers are advised to obtain the latest version of relevant
information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale
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CERTAIN APPLICATIONS USING SEMICONDUCTOR PRODUCTS MAY INVOLVE POTENTIAL RISKS OF DEATH, PERSONAL INJURY, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE ("CRITICAL APPLICATIONS"). CIRRUS PRODUCTS ARE NOT DESIGNED, AUTHORIZED OR WARRANTED FOR USE
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AND FITNESS FOR PARTICULAR PURPOSE, WITH REGARD TO ANY CIRRUS PRODUCT THAT IS USED IN SUCH A MANNER. IF THE CUSTOMER OR
CUSTOMER'S CUSTOMER USES OR PERMITS THE USE OF CIRRUS PRODUCTS IN CRITICAL APPLICATIONS, CUSTOMER AGREES, BY SUCH USE, TO
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Cirrus Logic, Cirrus, the Cirrus Logic logo designs, EXL Core, and the EXL Core logo design are trademarks of Cirrus Logic, Inc. All other brand and
product names in this document may be trademarks or service marks of their respective owners.
CAMCAL is a trademark or registered trademark of Energie-Messtechnik GmbH Meter Test Equipment AG.
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