Yes, it is best to check the type of input before connecting the reference. Even if the manual is missing maybe a visual inspection can reveal if the input is AC coupled or not and the possible input level.
On Thu, May 9, 2013 at 5:08 PM, Charles P. Steinmetz <[email protected]> wrote: > Azelio wrote: > >> Usually the external reference input of measuring equipment is >> internally squared, so if you feed a square or sine wave there should >> be no difference. > > > Some external reference inputs may be DC coupled and zero-switching, in > which case unipolar logic levels will not work well. I don't know of any > specific equipment to which this may apply, but if you try it and it doesn't > work well it is one thing to consider. An external coupling cap (or AC > coupling the output internal to divider) should fix it. > > Also, 74AC logic level (~ 5 Vpp) may be a little hot for some reference > inputs. Many reference inputs present a load impedance higher than 50 ohms > to the source (often ~ 1k ohm), so you may not get the divide-by-2 > attenuation from the open-circuit voltage that you expect in a matched > system. In this case, an external 50 ohm termination will reduce the level > to ~ 2.5 Vpp. > > Best regards, > > Charles > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
