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Common-Mode Bias Current

The NI 9234 uses common-mode bias current to bias the current-
limiting diodes when IEPE current is turned off. When the NI
9234 is using grounded signal sources, this current causes an
error that is dependent on the AI- lead impedance. This error is
approximately 50 ppm of range and 15 ppm of reading per ohm
of AI- impedance. The common-mode bias current causes an
error only with grounded sources and is not an issue with floating
signal sources. For best accuracy, use low-impedance leads when
connecting grounded signal sources.

NI 9234 Getting Started Guide

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© National Instruments

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Summary of Contents for NI 9234

Page 1: ...GETTING STARTED GUIDE NI 9234 4 AI 5 V 24 Bit 51 2 kS s ch Simultaneous AC DC Coupling IEPE AC Coupling...

Page 2: ...Refer to the documentation for each component in the system to determine the safety and EMC ratings for the entire system Safety Guidelines Operate the NI 9234 only as described in this document Cauti...

Page 3: ...referred to as MAINS voltage MAINS is a hazardous live electrical supply system that powers equipment This category is for measurements of voltages from specially protected secondary circuits Such vol...

Page 4: ...hese guidelines may result in serious injury or death Caution Do not disconnect I O side wires or connectors unless power has been switched off or the area is known to be nonhazardous Caution Do not r...

Page 5: ...arked II 3G and is suitable for use in Zone 2 hazardous locations in ambient temperatures of 40 C Ta 70 C If you are using the NI 9234 in Gas Group IIC hazardous locations you must use the device in a...

Page 6: ...he product specifications These requirements and limits provide reasonable protection against harmful interference when the product is operated in the intended operational electromagnetic environment...

Page 7: ...board applications To verify Lloyd s Register certification for a product visit ni com certification and search for the LR certificate or look for the Lloyd s Register mark on the product Caution In o...

Page 8: ...ications Operating temperature IEC 60068 2 1 IEC 60068 2 2 40 C to 70 C Operating humidity IEC 60068 2 78 10 RH to 90 RH noncondensing Pollution Degree 2 Maximum altitude 5 000 m Indoor use only Note...

Page 9: ...g the NI 9234 The NI 9234 provides connections to four simultaneously sampled analog input channels Figure 1 NI 9234 Pinout AI3 AI3 AI2 AI2 AI0 AI0 AI1 AI1 NI 9234 Getting Started Guide National Instr...

Page 10: ...t with each other the modules or the chassis Signal Descriptions Table 1 Signal Descriptions Signal Signal Description AI Provides DC excitation when enabled and positive input signal connection AI Pr...

Page 11: ...erential Signals You can connect floating differential signals to the NI 9234 Figure 2 Connecting Floating Differential Signals to the NI 9234 NI 9234 AI AI Signal Source NI 9234 Getting Started Guide...

Page 12: ...34 NI 9234 AI AI Signal Source Common Voltage Mode Make sure the voltage on the AI shell is in the common mode range to ensure proper operation of the NI 9234 The AI shell is protected against acciden...

Page 13: ...es an error that is dependent on the AI lead impedance This error is approximately 50 ppm of range and 15 ppm of reading per ohm of AI impedance The common mode bias current causes an error only with...

Page 14: ...to measure ground referenced or floating IEPE sensors Typical IEPE sensors have a case that is electrically isolated from the IEPE electronics so connecting the sensor to the NI 9234 results in a floa...

Page 15: ...on The NI 9234 provides overvoltage protection for each channel Note Refer to the device datasheet on ni com manuals for more information about overvoltage protection NI 9234 Getting Started Guide Nat...

Page 16: ...tware CompactRIO NI CompactDAQ RELATED INFORMATION C Series Documentation Resources ni com info cseriesdoc Services ni com services NI 9234 Datasheet NI RIO Help LabVIEW FPGA Help NI 9234 Datasheet NI...

Page 17: ...duct Product registration facilitates technical support and ensures that you receive important information updates from NI A Declaration of Conformity DoC is our claim of compliance with the Council o...

Page 18: ...cts technology refer to the appropriate location Help Patents in your software the patents txt file on your media or the National Instruments Patent Notice at ni com patents You can find information a...

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