NI 9247 Datasheet
- Updated2023-02-17
- 15 minute(s) read
NI 9247 Datasheet
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The NI 9247 current input module is a three channel 50 Arms module designed to support direct ring lug connectivity to three-phase high-current measurements of 1A and 5A current transformers (CTs). The NI 9247 is optimized for power, energy, and industrial applications that require continuous AC measurements up to 50 Arms, ±147 Apeak, and withstand over 1250 Arms for one cycle.
- Power quality monitoring and metering
- Utility pole-mounted smart switches
- Utility pole-mounted smart grid reclosers
- Substation merging units
- Industrial machine measurements
- Health monitoring
- Predictive maintenance and prognosis
- Phasor Measurement Units (PMUs)
NI C Series Overview
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NI provides more than 100 C Series modules for measurement, control, and communication applications. C Series modules can connect to any sensor or bus and allow for high-accuracy measurements that meet the demands of advanced data acquisition and control applications.
- Measurement-specific signal conditioning that connects to an array of sensors and signals
- Isolation options such as bank-to-bank, channel-to-channel, and channel-to-earth ground
- -40 °C to 70 °C temperature range to meet a variety of application and environmental needs
- Hot-swappable
The majority of C Series modules are supported in both CompactRIO and CompactDAQ platforms and you can move modules from one platform to the other with no modification.
CompactRIO
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CompactRIO combines an open-embedded architecture with small size, extreme ruggedness, and C Series modules in a platform powered by the NI LabVIEW reconfigurable I/O (RIO) architecture. Each system contains an FPGA for custom timing, triggering, and processing with a wide array of available modular I/O to meet any embedded application requirement. |
CompactDAQ
CompactDAQ is a portable, rugged data acquisition platform that integrates connectivity, data acquisition, and signal conditioning into modular I/O for directly interfacing to any sensor or signal. Using CompactDAQ with LabVIEW, you can easily customize how you acquire, analyze, visualize, and manage your measurement data. |
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Software
LabVIEW Professional Development System for Windows | |
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NI LabVIEW FPGA Module | |
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NI LabVIEW Real-Time Module | |
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NI 9247 Theory of Operation
The NI 9247 measures currents that flow into AI+ and out of AI- as positive polarity. A + or - symbol is molded into the plastic near the respective ring lug terminal for each channel. Each channel is independently isolated from other channels and earth ground. The isolation ratings of 300 Vrms to Earth and 480 Vrms between channels makes the inputs suitable for direct current measurements at line voltages up to 277 V/480 V Cat III three-phase service levels.
Circuitry
Each input signal of the NI 9247 is isolated, AC coupled, and then sampled by a single 24-bit ADC.
The NI 9247 is suited for connection to the outputs of current transformers with 1 A or 5 A nominal ratings.
DC Offset Currents
The NI 9247 inputs are AC coupled through an internal transformer. Refer to the section for information about the residual DC offset error the NI 9247 measures.
The DC value is ignored when you make frequency-specific measurements, such as harmonic analysis, phasor measurements, or fundamental line frequency amplitude measurements using algorithms such as those included with the NI LabVIEW Electrical Power Suite.
Performing Analysis with DC-Sensitive Algorithms
If you perform analyses with DC-sensitive algorithms, such as instantaneous absolute peak detection or absolute value measurements, you should first remove the DC component of your measured waveforms by using a high-pass digital filter or by subtracting the average value of an integer number of power line cycles from your measurements.
Correcting Faulty Measurements
Although the NI 9247 cannot measure DC inputs, excessive DC components in the input currents will saturate the internal transformer and cause erroneous measurements. Refer to the section for the typical limits of DC current that are tolerated before saturation begins. DC currents can occur in specific situations, such as with direct current measurements of a load. The following figure illustrates how faulty full-wave rectifiers in a load can cause half-wave rectification of a load, resulting in a DC offset.
With complete half-wave rectification, the DC component of the input current is 1/π x the peak current, and the RMS value is one half the peak current. In this scenario, the DC value must remain under the continuous allowed DC offset specification for correct measurements of the AC component of the waveform.
Performing Indirect Current Measurements
When you use the NI 9247 to indirectly measure current through a current transformer, the current transformer blocks continuous DC currents from reaching the inputs of the NI 9247. Temporary offsets of the AC signal can still occur. In a network modeled as a first order system with a reactance to resistance ration of X/R, short circuit faults result in an offset current that decays with a time constant equal to (X/R)÷2πfline. For example, in a network with an X/R ratio of 32 and a line frequency of 50 Hz, the offset decays with a time constant of 100 ms. An X/R of 120 at 60 Hz decays with a time constant of 320 ms, as shown in the following figure. Refer to the section for peak offset currents with first order decay limits. Peak offsets that exceed these limits can cause erroneous readings.
The following figure shows an excessive offset that causes saturation of the internal transformer and the resulting impact on measured current.
Filtering
The NI 9247 uses a combination of analog and digital filtering to provide an accurate representation of in-band signals and reject out-of-band signals. The filters discriminate between signals based on the frequency range, or bandwidth, of the signal. The three important bandwidths to consider are the passband, the stopband, and the anti-imaging bandwidth.
The NI 9247 represents signals within the passband, as quantified primarily by passband ripple and phase nonlinearity. All signals that appear in the alias-free bandwidth are either unaliased signals or signals that have been filtered by at least the amount of the stopband rejection.
Passband
The signals within the passband have frequency-dependent gain or attenuation. The small amount of variation in gain with respect to frequency is called the passband flatness. The digital filters of the NI 9247 adjust the frequency range of the passband to match the data rate. Therefore, the amount of gain or attenuation at a given frequency depends on the data rate.
Stopband
The filter significantly attenuates all signals above the stopband frequency. The primary goal of the filter is to prevent aliasing. Therefore, the stopband frequency scales precisely with the data rate. The stopband rejection is the minimum amount of attenuation applied by the filter to all signals with frequencies within the stopband.
Alias-Free Bandwidth
Any signals that appear in the alias-free bandwidth are not aliased artifacts of signals at a higher frequency. The alias-free bandwidth is defined by the ability of the filter to reject frequencies above the stopband frequency. The alias-free bandwidth is equal to the data rate minus the stopband frequency.
Data Rates
The frequency of a master timebase (fM) controls the data rate (fs) of the NI 9247. The NI 9247 includes an internal master timebase with a frequency of 12.8 MHz, but the module also can accept an external master timebase or export its own master timebase. To synchronize the data rate of an NI 9247 with other modules that use master timebases to control sampling, all of the modules must share a single master timebase source.
The following equation provides the available data rates of the NI 9247:
where n is any integer from 1 to 31.
However, the data rate must remain within the appropriate data rate range. When using the internal master timebase of 12.8 MHz, the result is data rates of 50 kS/s, 25 kS/s, 16.667 kS/s, and so on down to 1.613 kS/s depending on the value of n. When using an external timebase with a frequency other than 12.8 MHz, the NI 9247 has a different set of data rates.
NI 9247 Specifications
The following specifications are typical for the range -40 °C to 70 °C unless otherwise noted.
Input Characteristics
Number of channels | 3 analog input channels | ||||||
ADC resolution | 24 bits | ||||||
Type of ADC | Delta-Sigma (with analog prefiltering) | ||||||
Sampling mode | Simultaneous | ||||||
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Typical scaling coefficient | 17.522 μA/LSB | ||||||
Operating input rating | 50 Arms; 100 Arms for 10 seconds, not to repeat more than once in 30 minutes | ||||||
Overcurrent withstand rating | 500 Arms for 1 second, not to repeat more than once in 30 minutes; 1250 Arms for 1 cycle (20 ms), not to repeat more than once in a minute | ||||||
Input coupling | AC | ||||||
Input impedance | 0.2 mΩ | ||||||
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Data rates (fs)
Passband frequency | 10 Hz to 0.453 · fs | ||||||
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Alias-free bandwidth | 0.453 · fs | ||||||
Stopband frequency | 0.547 · fs | ||||||
Stopband attenuation | 95 dB | ||||||
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Measurement Conditions | Percent of Reading (Gain Error or Amplitude Accuracy) | |
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1 Arms to 45 Arms | 0 Arms to 100 Arms | |
Calibrated typical (23 °C, ±5 °C) | 0.15% | 0.3% |
Calibrated max (-40 °C to 70 °C) | 0.5% | 1.0% |
Uncalibrated[3] typical (23 °C, ±5 °C) | 1.0% | 1.2% |
Uncalibrated3 max (-40 °C to 70 °C) | 2.5% | 3.0% |
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Gain drift | ±15 ppm/°C | ||||||||
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Input delay | (40 + [5/512])/fs + 3.2 μs |
Measurement Conditions | Phase Error[4] | |
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10 Hz to 45 Hz | 45 Hz to 1920 Hz | |
Typical (23 °C, ±5 °C) | 0.2° | 0.05° |
Max (-40 °C to 70 °C) | 0.5° | 0.11° |
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Additional phase error, 45 Arms to 100 Arms | ±0.02°/Arms | ||||||||
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Common Mode Rejection Ratio (CMRR) | 7.5 μA/V/Hz (375 μA/V at 50 Hz) | ||||||
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Power Requirements
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Physical Characteristics
If you need to clean the module, wipe it with a dry towel.
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Recommended torque | 1.4 N · m (12 lb · in.) | ||||||
Weight | 248 g (8.75 oz) |
Safety Voltages
Connect only voltages that are within the following limits:
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Safety
This product is designed to meet the requirements of the following electrical equipment safety standards for measurement, control, and laboratory use:
- IEC 61010-1, EN 61010-1
- UL 61010-1, CSA 61010-1
Electromagnetic Compatibility
This product meets the requirements of the following EMC standards for electrical equipment for measurement, control, and laboratory use:
- EN 61326-1 (IEC 61326-1): Class A emissions; Industrial immunity
- EN 55011 (CISPR 11): Group 1, Class A emissions
- EN 55022 (CISPR 22): Class A emissions
- EN 55024 (CISPR 24): Immunity
- AS/NZS CISPR 11: Group 1, Class A emissions
- AS/NZS CISPR 22: Class A emissions
- FCC 47 CFR Part 15B: Class A emissions
- ICES-001: Class A emissions
CE Compliance
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This product meets the essential requirements of applicable European Directives, as follows:
- 2014/35/EU; Low-Voltage Directive (safety)
- 2014/30/EU; Electromagnetic Compatibility Directive (EMC)
Product Certifications and Declarations
Refer to the product Declaration of Conformity (DoC) for additional regulatory compliance information. To obtain product certifications and the DoC for NI products, visit ni.com/product-certifications, search by model number, and click the appropriate link.
Shock and Vibration
To meet these specifications, you must panel mount the system.
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Operating shock (IEC 60068-2-27) | 30 g, 11 ms half sine; 50 g, 3 ms half sine; 18 shocks at 6 orientations |
Environmental
Refer to the manual for the chassis you are using for more information about meeting these specifications.
Operating temperature (IEC 60068-2-1, IEC 60068-2-2) | -40 °C to 70 °C |
Storage temperature (IEC 60068-2-1, IEC 60068-2-2) | -40 °C to 85 °C |
Ingress protection (with power plug attached) | IP 40 |
Operating humidity (IEC 60068-2-78) | 10% RH to 90% RH, noncondensing |
Storage humidity (IEC 60068-2-78) | 5% RH to 95% RH, noncondensing |
Pollution Degree | 2 |
Maximum altitude | 5,000 m |
Indoor use only.
Environmental Management
NI is committed to designing and manufacturing products in an environmentally responsible manner. NI recognizes that eliminating certain hazardous substances from our products is beneficial to the environment and to NI customers.
For additional environmental information, refer to the Engineering a Healthy Planet web page at ni.com/environment. This page contains the environmental regulations and directives with which NI complies, as well as other environmental information not included in this document.
EU and UK Customers
电子信息产品污染控制管理办法(中国RoHS)
Calibration
Calibration interval | 1 year |
1 Flatness refers to the difference in gain/error between any frequency in the defined range, with a reference frequency of 50 Hz or 60 Hz.
2 When measuring the amplitude of the fundamental frequency over a single power line cycle, the measurement bandwidth is 0.5 fline to 1.5 fline.
3 Uncalibrated accuracy refers to the accuracy achieved when acquiring data in raw or unscaled modes and in which calibration constants that are stored in the module are not applied to the data.
4 Phase error is the deviation in measured phase relative to the nominal input delay.