Anyone any clever ideas.....
tegwin - 2/12/08 at 08:18 PM
I have an old Smiths (RVI) induction type tacho for my 6 Cyl engine....
It doesnt work!
I cant find a fault in it...but it does not work none the less....
Ideally I want to convert it to the current sensing type.... That type is MUCH less prone to interference from after market electronic ignition
systems and fuel pumps etc...
Is it possible to build a circuit that does the current sencing job, and then passes the signal onto the tacho motor coils?
Or, does anyone know of any other 6Cyl simple style tachos that I could pinch the electronics/mechanism out of?
The tacho looks like this (or rather, it did until I pulled it appart!):
[Edited on 2/12/08 by tegwin]
MikeRJ - 2/12/08 at 08:43 PM
The RVI is a current sensing tachometer. Converting it to a voltage sensing type like the RVC is the way to go. The following may be
useful...
http://members.shaw.ca/tsmit/tachmod/tachmod.html
http://www.britishcarforum.com/lore/attachment.php?id=12
r1_pete - 2/12/08 at 09:12 PM
I thought the RVI had the inductive loop, I - Inductive.
From the look of it yours is an RVC, current sensing from the switched side of the coil. My MGB RVC works fine from the MJLJ tach out or via diodes
from the switched side of the two coils.
BTW make sure you have a good earth to the unit.
[Edited on 2/12/08 by r1_pete]
tegwin - 2/12/08 at 09:28 PM
It deffinately says RVI on the front...
And it has an induction type transformer thingie inside the casing....
That circuit diagram looks pretty tidy... wonder if it will actually work.... slightly confused as to how his callibration circuit works....but worth
a try...
Donners90 - 2/12/08 at 10:49 PM
You could talk to these guys. They recon'd a smiths water temp/oil pressure guage and replaced the capiliary. 4 day turnaround, including the
postage. Drop them an email and they might be able to help/ advise as to the best root
http://www.speedograph-richfield.com/html/speedometer.html
02GF74 - 3/12/08 at 10:15 AM
u have u2u
MikeRJ - 3/12/08 at 10:31 AM
quote:
Originally posted by r1_pete
I thought the RVI had the inductive loop, I - Inductive.
Correct, and the inductive coupling senses the current in the coil wire, hence it's a current sensing tachometer.
The C in RVC does not stand for current (not a clue what it standard for to be honest), it's a voltage sensing tachometer which is connected
directly to the coil.
peterparsons - 3/12/08 at 03:26 PM
Also take a look at www.speedycables.co.uk
They overhalled my tacho, three day turnaround, excellent job too.