NOTE: Utility distribution and transmission levels will always use external sensors (CTs/PTs).įigure 3. A power strip connected to a residential outlet is used for demonstration purposes but this concept scales from individual appliances on residential service levels (120VAC/240VAC), all the way to utility voltages. The following illustrations show how to physically connect modules to a circuit for current measurement. Both modules can withstand 500 ARMS for 1 second and 1250 ARMS for 1 cycle. Direct measurements with these modules will be more accurate and with a higher frequency response than using most external CTs/sensors. The NI 9246 and NI 9247 modules have CTs built into the module, large over-current ratings, and accommodate up to 10AWG wire with ring lugs for higher current measurement. Shields are available (right), and recommended, for strain relief and operator keep-outs from connections to active circuits.įigure 2. The NI 9229, NI 9239, NI 9227, and NI 9238 have a two terminal connector (left) for each measurement channel. All modules output full waveform for processing with LabVIEW or other measurement and analysis software.įigure 1.

NI has a variety of C Series modules for current measurement. Channel synchronization is needed for more accurate phase and power measurements.Ĭonnect to current sensors with ☑0V or ☖0V outputĬonnect to current sensors with 0.333 VRMS output and external shuntsĭirect connection to module that has internal, calibrated shuntsĭirect connection to module that has internal, calibrated CTs OR connect to 1 A and 5A secondary from high current CTs Current and Voltage measurement modules from tables 1 and 2 respectively are synchronized when installed together in either a CompactDAQ or CompactRIO chassis.

Table 1 shows modules compatible with CompactRIO chassis and CompactDAQ chassis for current measurement.Īll modules listed in table 1 use simultaneous sampled inputs with a 50kS/s 24-bit ADC per channel. NI has a variety of hardware options for both direct measurement with a module and connection to external sensors and conditioning equipment. From an instrumentation standpoint, current measurements are made with front end conditioning or sensors such as shunts, current transformers (CT), hall-effect sensors, and Rogowski coils.

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