Synchronizing Waveform Measurements
For the NI 4070/4071/4072 only, when synchronizing multiple NI 407x devices, ensure that the measurement settling times and triggering are configured similarly. For example, if you enable Auto Zero on only one of the multiple NI 4070/4071/4072 devices or have different sampling rates, this increases the phase shift between the measured waveforms. Also, you must ensure that triggers are received from the same source on each NI 4070/4071/4072.
Power measurements are an example of an application in which synchronization of multiple NI 4070/4071/4072 devices is beneficial. One NI 4070/4071/4072 can acquire current while the other acquires voltage. Using the data collected from these two sources and Ohm's Law, you can determine the power. For an accurate representation of power, it is critical for these measurements to be synchronized.
To ensure that the two devices start the waveform acquisitions at the same time, you must configure the same external hardware trigger for each device. You should also set the settling time for each device to the same value. Normally, NI-DMM chooses the optimal settling time based on function and range parameters.
For example, to capture a voltage waveform in 300 V range and a current waveform in 1 A range, set the settling time for both measurements to 2 ms (this is the settling time required by the 300 V range and it is greater than 100 us required by 1 A range). The default settling times for voltage and current waveforms are different.