The best option is to use LabChart's Digital Filters. Digital Filters can be turned on or off at will, so your raw signal will not be affected.
To access the Digital Filter option within LabChart, choose an unused channel, and select the Channel's name at the right-hand side. From the resulting drop-down menu, choose Digital Filter - this will allow the application of a variety of filters without affecting the recording. You can use a narrow band-stop filter to mimic a 50Hz filter.
However, in case the Digital band-stop or notch filter does not work as effectively as the Mains Filter, it is often possible to setup LabChart so that the PowerLab is sampling continuously even though you are using a fixed duration triggered mode. LabChart will generally use this continuous sampling mode unless the Stimulator is turned on, in which case it has to stop and start the PowerLab for each block so that the Stimulator starts at the start of the recording.
However, if in the Sampling dialog you set the Trigger Source to Stimulator, then LabChart can use the continuous sampling mode even though the Stimulator is running, with the result that the Mains Filter should be usable.
For further technical assistance with this or any other issue, please contact ADInstruments Technical Support by clicking HERE