Hello Guest it is April 23, 2021, 04:19:07 AM

Author Topic: input read frequency?  (Read 8960 times)

0 Members and 1 Guest are viewing this topic.

Offline stirling

*
  • *
  •  2,188 2,188
  • UK
    • View Profile
    • www.razordance.co.uk
input read frequency?
« on: May 07, 2010, 11:34:12 AM »
I'm sure I've read this somewhere but can't find it. How often does Mach read input signals - I have in mind it's somewhere like 100Hz but I'm not sure. Specifically if it makes any difference - how often does Mach read THC UP/DOWN?

Cheers

Ian

Offline Hood

*
  •  25,838 25,838
  • Carnoustie, Scotland
    • View Profile
Re: input read frequency?
« Reply #1 on: May 07, 2010, 11:36:31 AM »
10Hz update at the moment for Mach, Rev 4 will be faster.

Hood

Offline stirling

*
  • *
  •  2,188 2,188
  • UK
    • View Profile
    • www.razordance.co.uk
Re: input read frequency?
« Reply #2 on: May 07, 2010, 11:39:08 AM »
Thanks Hood - Looks like I was being a bit optimistic with my 100Hz.

Cheers

Ian

Offline Hood

*
  •  25,838 25,838
  • Carnoustie, Scotland
    • View Profile
Re: input read frequency?
« Reply #3 on: May 07, 2010, 12:04:17 PM »
Yep, just a bit ;D
I tested Rev4 at 100Hz and wow what a difference but there were issues so think it was dropped back to 50HZ but its been a while so not 100% sure on that.

Hood
Re: input read frequency?
« Reply #4 on: May 07, 2010, 01:50:07 PM »
hi, the signs of input for Home also is read each 100ms?. Then would have a error in zero machine, this is correct?
I think which the measurement should be done in less time, minor a 10ms.

regards

Offline Hood

*
  •  25,838 25,838
  • Carnoustie, Scotland
    • View Profile
Re: input read frequency?
« Reply #5 on: May 07, 2010, 02:51:16 PM »
Not really sure I understand what you are saying but if the Home position is read at the same update rate every time then it should be accurate. Changing the axis  homing speed from one home to another will however make for inaccuracies.
Hood

Offline stirling

*
  • *
  •  2,188 2,188
  • UK
    • View Profile
    • www.razordance.co.uk
Re: input read frequency?
« Reply #6 on: May 08, 2010, 04:56:43 AM »
I'm probably a bit slow and everyone else already knows this but... Re: probing - this must mean that in order to probe at the best resolution your machine is capable of you MUST probe at less than 10 steps per second right?

Ian

Offline BR549

*
  •  6,952 6,952
    • View Profile
Re: input read frequency?
« Reply #7 on: May 08, 2010, 11:44:48 AM »
Ian I have found IF you calibrate your probe to the known probing speed then that accounts for the latency of Mach.

The probe here repeats well inside of .001"

Offline stirling

*
  • *
  •  2,188 2,188
  • UK
    • View Profile
    • www.razordance.co.uk
Re: input read frequency?
« Reply #8 on: May 08, 2010, 12:41:57 PM »
But what's the accuracy of your machine Terry?

Offline stirling

*
  • *
  •  2,188 2,188
  • UK
    • View Profile
    • www.razordance.co.uk
Re: input read frequency?
« Reply #9 on: May 08, 2010, 01:36:13 PM »
Anyway - back to my original reason for asking the question. Mach will raise and lower the Z for THC according to the inputs THC UP/DOWN. BUT - as the rate of update of inputs - i.e. THC UP/DOWN is only 10Hz then (for example) Mach could still be raising Z for a 1/10th of a sec after the THC UP has actually gone inactive. Not ideal. Yet from another thread active at the moment concerning the monitoring of spindle rpm, it would appear that the index input is special - i.e. it MUST be updating faster than 10Hz otherwise it could only monitor a well slow spindle. This seems strange - if Mach can handle the index input at a "decent" frequency - why not THC UP/DOWN? - Just trying to understand the implications for my own THC design.

Cheers

Ian