Hi all.

I want to check your practice of setting key phasor probe gap voltage if it is same as vibration probe gapping (approx. -10 Vdc). I've encountered a case recently of a Bently 7200 key phasor card which could not read speed until the gab was reduced to below -6 VDC and according to the instrumentation people -6 Vdc is their normal practice. I other words, are there different linear ranges?

Also, what is the effect on the card configuration if the once per revolution signal is generated by a notch (within the linear range of the probe) or deep keyway?

Thx-AMS

Not all gap voltages are the same but the 7200 @~10 sound Hoyleish. Can you have a freak incident? Such as reading the side of the hole and collar. I would throughly check it out. Maybe if your practice is to monitor voltage while screwing the probe in - change the method and gently run the probe down aginst the collar (not running of course) and they back it off. And make sure the hole is of correct diameter. Maybe someone else will weight in that has encounter this phenomenon; I haven't had this problem so far. Of course you are starting with the collar centered.

The points brought out here about notch size, being on the edge of a notch, etc. should be investigated because most systems should work fine at -10 vDC with a well designed notch and proper transducer mount, and matching compoents in the transducer system.

Having said that, the 7200 series monitor can be optioned for either -18 volt DC) power to proximitors or -24 vDC. On the -18 vDC system the recommended gap for radial vibration probes is something around -8 vDC as this will put you in the middle of the linear portion of the physical gap vs. DC voltage curve for older transducers. On the -24 vDC system the middle of the linear porton of the GAP vs voltage curve will put you at about -10 to -11 vDC.

Also, it is generally a good idea to gap KØ probes "short" (more positive, example -6 vDC on a -18 vDC system; -8 on a -24 vDC system) to insure a good voltage spike as it passes a notch.