Hi i have a TB6600 board controlled with mach3.
Now i want to control my Sysdrive  3G3EV with the 0-10V output. But the HZ on display is very unstable, but always same value, if i say 100rpm it always show 8,4-10 in the display and so on. If i use a volt meter the output seems very stable, and increases smoothly for 0-10V. My inverter is set up to 0-50HZ. And mach 3 from 0-1000rpm, and setup for step/dir.

In this video i triede measure volt and film the inverter display at 10 - 20 - 30 - 40 - 50 - 60 - 70 - 80 - 90 - 100RPM
https://www.dropbox.com/s/2wslc92nfx1gy36/2014-12-08%2019.45.35.mp4?dl=0


Under her i do some readouts. The strange thing is the sometime the readout drops a lot by changing 10RPM.
The RPM is the one i put out from MACH3, and dont match the real rpm.
10 RPM reads 0,9volt and the inverter show 1,7
100 RPM reads 1,71volts  and the inverter is unstable and show between 8,4 - 10
200 RPM reads 3,2 volts and inverter is more stable at 7,,7
300 RPM, inverter shows 10,5-11
400 RPM, inverter shows 7,5
500 RPM, inverter shows 11
550 RPM, inverter shows 9
600 RPM, inverter shows 12
650 RPM, inverter shows 22-23
700 RPM inverter shows 42-43
800 RPM, inverter shows 37-38
900 RPM, inverter shows 48
1000 RPM, inverter shows 49,9-50

Could the 10V out be a pulse signal that my inverter cant figure out?

Hope you understand my question and explanation.