We purchased a TDR100+SDMX50 equipment with the aim of measuring variations in the dielectric constant of wood. the problem is that our wood samples are relatively small, and the 75 mm rods are too long.
I suppose that shortening the probe rods to 50 mm should not be a problem, provided that the new length is passed to the TDR100 Cr-basic instruction, but I would appreciate the opinion of CS gurus. And also: should we recalculate the offset for each probe?
Thanks in advance
Luca Testi
Shortening the probes is OK. Theoretically the offset should not change as it is a function of the termination inside the block of plastic.
Estimating the offset again is complicated normally involving putting the probe in solutions of known dielectric constant (many of which are nasty chemicals)
Shortening the rods will however make the measurement coarser (with more errors) as you are effectively using less samples (for time/distance) for your analysis of the signal.
Along time ago I had someone knock six inch nails in a tree to do this measurement and they did get good comparative data although the absolute accuracy was questionable.
Many thanks.
Luca