Need Help!- Not getting the right speed of spindle via Mach3

[Vaffel]

Hi,

Ive connected the Huanyang VFD + spindle to Mach3 via Gecko 540.

When starting the spindle at 6000 rpm (of the 24.000 max), the frequency on the VFD is showing as 150Hz (The correct is 100Hz)

Setting at 12000 rpm, its showing 188 Hz.
At 24000 rpm, its showing 214 Hz

So, Im only getting a short span of the real spindle rpm.

When measuring the voltage on the Vi and ACM terminals on the VFD without spindle running, its showing the right voltage. 24.000rpm in Mach3 outputs 10V on this terminal. (5Vs for 12.000 etc).

When I have the spindle running, Im getting a wierd result when measuring. When I stick the negative measuring pin to the Vi terminal (the postive terminal to nothing), the spindle speed is turned down a notch, and I get a voltage read. How can I get a voltage read when only ONE measuring pin is connected to something? And the voltage read is not correct.

Im sure the positive measuring pin isn't touching ground or anything else.

Please help!!



Some setup:

The PD71-75 is set to minimum frequency at 0Hz, max freq at 400Hz, and only positive direction is set.

[vger]

Sounds like you may have a noise spike on the line going to the VI terminal. A meter will sometimes read a value with only one probe attached if there is high frequency on the one probe.
How do you have the G540 connected to the VFD? Make sure your analog wires do not run near the motor leads, and use twisted pair sheilded wire for the analog wires if possible.

[Vaffel]

Originally Posted by vger Sounds like you may have a noise spike on the line going to the VI terminal. A meter will sometimes read a value with only one probe attached if there is high frequency on the one probe. How do you have the G540 connected to the VFD? Make sure your analog wires do not run near the motor leads, and use twisted pair sheilded wire for the analog wires if possible.

Thanks for the answer!

How near is 'near', actually? The first time I tried this was using a Firewire-cable, which is extensivly shielded and twisted. However, I think the leads was too small - and the drop in voltage was too significant.

But I will try once more and try to minimise the signal interference!

The last time I tried this, I got increased voltage on the signal terminal (18-30V). I dont understand this stuff...