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Linear scale not recognized on Acu-Rite D200 3x turn DRO


Feb 12, 2024
Central europe
I purchased a 3rd linear scale to add to the acu-rite d200 3x turn DRO. Of course, I am having trouble getting it to work.

The linear scale is a cheap chinese brand (vevor). The quality is adequate for my purpose, and has been verified to work on its own DRO.

I am unsure what the pin configuration is on the Acu Rite D200 DRO. It seems like default TTL looking at a manual I found online.

On the linear scale side, it also seems to be default TTL.

As for the signals, both are square waves, with 90degree phase difference.

I verified the port on the dro is working, swapping cables isn’t an issue with the already mounted scales.

Anyone with more experience here that could pinpoint what could be going wrong? The DRO is quite old and it hasn’t been straightforward finding diagrams for it.

I have attached the technical info that came with the scale, as well as the DRO’s serial number.

I have found the technical specs for one of the scales that is already installed and working (Acu-Rite AR5). Unfortunately the manual does not include any info regarding the bendix->vga connection.

Could it be due to the voltage difference? 5.1+-0.1 vs 5+-0.25? I don't know enough about electronics to know if this could be an issue. I would imagine if it was the case, the slightly higher voltage scale would still work on the cheap Chinese DRO that is expecting a lower voltage. At least, when speaking in the 0.1v range...

Still at a loss why this isn't compatible..

Screenshot 2024-04-16 at 13.32.43.png
Last edited:
Issue resolved, in the end the only issue was the pin configuration being different. For completeness:

Acu-rite pin configuration:
1: /
2: A+
3: A-
4: B+
5: B-
6: 0V
7: 5V
8: Z+
9: Z-

Vevor linear scale pin configuration:
1: A-
2: 0V
3: B-
4: /
5: Z-
6: A+
7: 5V
8: B+
9: Z+