Chapter 4 Analog Input© National Instruments Corporation 4-31 M Series User Manualai/SampleClockTimebase is not available as an output on the I/O connector.ai/SampleClockTimebase is divided down to provide one of the possiblesources for ai/SampleClock. You can configure the polarity selection forai/SampleClockTimebase as either rising or falling edge.AI Convert Clock SignalUse the AI Convert Clock (ai/ConvertClock) signal to initiate a single A/Dconversion on a single channel. A sample (controlled by the AI SampleClock) consists of one or more conversions.You can specify either an internal or external signal as the source ofai/ConvertClock. You also can specify whether the measurement samplebegins on the rising edge or falling edge of ai/ConvertClock.With NI-DAQmx 7.4 and later, the driver chooses the fastest conversionrate possible based on the speed of the A/D converter and adds 10 μs ofpadding between each channel to allow for adequate settling time. Thisscheme enables the channels to approximate simultaneous sampling andstill allow for adequate settling time. If the AI Sample Clock rate is too fastto allow for this 10 μs of padding, NI-DAQmx chooses the conversion rateso that the AI Convert Clock pulses are evenly spaced throughout thesample.With NI-DAQmx 7.3, the driver chooses a conversion rate so the AIConvert Clock pulses are evenly spaced throughout the sample. This allowsfor the maximum settling time between conversions. To approximatesimultaneous sampling, manually increase the conversion rate.To explicitly specify the conversion rate, use AI Convert Clock RateDAQmx Timing property node or function.Caution Setting the conversion rate higher than the maximum rate specified for yourdevice will result in errors.
