Encoder for axis tacho feed back

It appears that I have damaged The mesa 7i83 , because when a ENAn is enabled by hal,
resistance between ENAn+ and ENAn- show 14k ohm resistance,
and when not enabled mega ohms (open circuit)

That is probably OK since the enable OPTOs are Darlingtinon type
and have a fixed 0.7V or so drop regardless of current so tend to read
high on Ohmmeters (you could check another enable output to verify)

Thanks PCW ,

I just could not see the tree for, the forrest.
Tacho feedback working, It seems so simple now.

setp hm2_5i24.0.7i83.0.4.analogout4-maxlim 278
setp hm2_5i24.0.7i83.0.4.analogout4-minlim -278
setp hm2_5i24.0.7i83.0.4.analogout4-scalemax 278

net mcc-y hm2_5i24.0.7i83.0.4.analogena4
net y-tacho-out hm2_5i24.0.7i83.0.4.analogout4

cheers john

The encoder tacho feed back, is used with a fanuc servo amp and series 20 servo motors ,which worked flawlessly before the refit.
The x and y axis move correctly and smoothly in a negative direction.
The x and y axis shudder violently when trying to move in a positive direction.
I have not been able to tune this out at all.
Any suggestions most welcome.
cheers john

Signal from tacho - ALWAYS POSITIVE!

As I remember from my tries of tuning of servodrive with tacho:
0) Disconect motor from mechanic
1) Control voltage from linuxcnc should be disconnected (I don't mean tacho feedback)
2) Enable servodrive and look how it behaves. It should stand still or have slow movement. If it runs away then change taho-pins vice-versa
3) Check also direction of encoder feedback to linuxcnc
4) Adjust ofset of servodrive that it stans still or better as you can
5) Adjust on servodrive Gain and Tachofeedback
6) Adjust in linuxcnc gains, FF1 and other parameters
7) If everything works fine connect to mechanical side

Velocity servo system with tacho should always move slowly when enabled and no voltage applied to input, not stand still.

Good day ,
Thanks for the replies,
At the moment it looks like the fanuc pulse coders only supply a negative
going pulse .
The linuxcnc machine config page encoder velocity, shows minus - (pulse count )when jogging minus.
when trying to jog positive the jog count is trying to give a negative pulse code.
I believe the fanuc pulse counter must be only counting negative pulse.

So I will try a non fanuc encoder, do not know how long that will take .
Thanks again for the replies
cheers john