Error -1802: Waveforms Have Different dt Values

Updated Jan 3, 2024

Reported In


  • LabVIEW Base
  • LabVIEW Full
  • LabVIEW Professional


  • NI-DAQmx

Issue Details

Why do I see Error -1802: Waveforms have different dt values (shown in the following dialogue) when performing mathematic or analytical operations on waveforms in LabVIEW?


This error results from an attempt to perform mathematical operations on waveforms whose dt values differ from each other, meaning that the two waveforms are being sampled at different points in time (seen below).

In order to avoid this error, make sure that all waveforms being operated on are sampled at the same rate to ensure that their dt values are equal. This recommendation applies both to DAQ tasks and simulated waveforms generated with the Waveform Generation VIs.

In order to correct dt inconsistencies in already existing waveform data, two methods exist:
  1. Use the Scale Delta t VI located on the Functions»Programming»Waveform palette to automatically scale the dt of one of the waveforms to match the dt of the other. 
  1. Use the Align Waveforms VI located on the Functions»Signal Processing»Waveform Conditioning palette. The specific VI used will depend on whether the input is a single waveform, in which case you would use the Align Waveforms (Single Shot) VI; or a continuously updated waveform, in which case you would use the Align Waveforms (Continuous) VI.