Way back machine... GE accupins

[samco]

So - we are well on our way finally to finishing the big retrofit. This is of a Kearney and Trecker hmc. This thing was designed in the 60's and delivered in 69'.

One thing we would like to get working again is the accupin scales. With the original controller - we never had position issues (and they are already on the machine). These are 'not' inducto scales if I understand it right.

This is what the head reads
http://electronicsam.com/images/Kand...n/accupins.JPG
The old controller divided each .1" into 1000 divisions giving the machine a resolution of .0001.

Here is the head drive circuit
http://electronicsam.com/images/Kand...rsion/accu.pdf
(you have to rotate the pdf -sorry)

Now - from what I gather from reading the schematic and other things..

there are 4 coils - they are hooked up in a center tap config (see schem) - 2 sets of 2 coils. An excitation signal (250khz square wave) is sent to the outside connections of the 2 center tapped coils. The center taps are summed together and turned into a square wave. That square wave is shifted compared to the exciter signal depending on the position relative to the .1 pin.

Now the way I think the controller did it was this - it had a 250khz clock - they used this to count the shift between the exciter signal and the summed square wave back from the center taps. this would give you 250khz/250hz - 1000 divisions within each pin.

So - the question is - does someone make a circuit to drive these things? Or do I have to make something up?

thanks
sam

[samco]

top is the read head - bottom agian is the pins.

http://electronicsam.com/images/Kand...accpinset1.jpg

sam