From: [email protected]
Date: 23 Apr 2002
Time: 20:30:19
Remote Name: 213.235.5.109
Ron, I have been working on electronic rev counters for some time. Here are a few pointers to get you going. 1. The XJ6 meter is set up for 6 cylinders, so in a perfect world it will read 0.66 low. ie 3000rpm on the Austin will read 2000rpm on the XJ6 meter. 2. You could get 6v operation by doubling the pulse width of the monostable inside the instrument.
The upshot of 1 and 2 is that you need to increase the pulse width by about 3. The easiest way to do this is to open up the instrument and locate the potentiometer on the board. Its the obviously adjustable component you can see. Measure its value and replace it with one about four times larger. You then have to set the pot accurately by adjusting it to read correctly against a known rpm.
The other gotcha is the +ve or -ve earth question! Don't mix an instrument of one flavour with a wiring system of the other!
email me if you have any questions....I have the wiring diagram of the Smiths RVI instrument, but not with me as I write this reply.
Sean Smedley.