National Instruments E Series User Manual

Also see for E Series: Programmer's manual User manual User manual User manual User manual

Contents

National Instruments E Series User Manual Manual pdf 54 page image

Chapter 4 Signal ConnectionsDAQCard E Series User Manual4-18 National Instruments CorporationSingle-Ended Connection ConsiderationsA single-ended connection is one in which the DAQCard E Series cardanalog input signal is referenced to a ground that can be shared withother input signals. The input signal is tied to the positive input of thePGIA, and the ground is tied to the negative input of the PGIA.When every channel is configured for single-ended input, up to 16analog input channels are available.Use single-ended input connections for any input signal that meets thefollowing conditions:• The input signal is high level (greater than 1 V).• The leads connecting the signal to the DAQCard are less than 10 ft(3 m).• The input signal can share a common reference point with othersignals.DIFF input connections are recommended for greater signal integrityfor any input signal that does not meet the preceding conditions.You can software-configure the DAQCard channels for two differenttypes of single-ended connections—RSE configuration and NRSEconfiguration. Use the RSE configuration for floating signal sources;in this case, the DAQCard provides the reference ground point for theexternal signal. Use the NRSE input configuration for ground-referenced signal sources; in this case, the external signal supplies itsown reference ground point and the DAQCard should not supply one.In single-ended configurations, more electrostatic and magnetic noisecouples into the signal connections than in differential configurations.The coupling is the result of differences in the signal path. Magneticcoupling is proportional to the area between the two signal conductors.Electrical coupling is a function of how much the electric field differsbetween the two conductors.