PlasmaC Fiber laser 1Kw head height control + auto focuas

there is no much noise from the system,, 10 bit is good for me
but how can the low pass filtering effect the resolution

Because the THCAD is a V-F converter. It has an output frequency range of
about 100 KHz to about 1 MHz. LinuxCNC reads this frequency by measuring
counts per servo thread period, so if the servo thread period is 1 ms , full scale
volts will read about 1000 counts per servo period (roughly 10 bits of resolution)
If you chose a longer servo period you would have more counts and higher resolution
A low pass filter has a similar effect, that is, the more the frequency output is averaged,
the higher the resolution.

I would try the 9V battery, you should not see 1% of full scale noise, only about 0.12%
(at 1 ms servo thread)

PCW wrote:

there is no much noise from the system,, 10 bit is good for me
but how can the low pass filtering effect the resolution

Because the THCAD is a V-F converter. It has an output frequency range of
about 100 KHz to about 1 MHz. LinuxCNC reads this frequency by measuring
counts per servo thread period, so if the servo thread period is 1 ms , full scale
volts will read about 1000 counts per servo period (roughly 10 bits of resolution)
If you chose a longer servo period you would have more counts and higher resolution
A low pass filter has a similar effect, that is, the more the frequency output is averaged,
the higher the resolution.

I would try the 9V battery, you should not see 1% of full scale noise, only about 0.12%
(at 1 ms servo thread)

with or without lowpass?
with lowpass im having 0.12%

Without lowpass

At 1 ms servo thread and full scale input from a noiseless source
(9V battery or just inputs shorted) you should have about 0.12%
( of full scale value ) noise, that is, if you have your
scaling set so that you are reading volts (10V full scale)
you should expect about +- 12 mv of noise

PCW wrote: Without lowpass

At 1 ms servo thread and full scale input from a noiseless source
(9V battery or just inputs shorted) you should have about 0.12%
( of full scale value ) noise, that is, if you have your
scaling set so that you are reading volts (10V full scale)
you should expect about +- 12 mv of noise

whats the maximum frequency that can be read with mesa 7i92 and 7i96 encoder input. THCAD makes 100khz ~1MHZ... if its 1MHZ ~10MHZ is it will give better performance... am i right?
because i will build capacitance to frequency converter and i will build it based on maximum mesa count rate

im using 3 axis (and 4th is focus) step/pulse and 1 encoder

Depending on the input circuitry most Mesa non-multiplexed encoder inputs are
capable of reading to 5-10 MHz. Note that if you have that high a frequency, you pretty much need differential data transmission.

cutting speed about 27m/min and the space between the head and workpeace is about 0.8mm
do you think its enough to use THCAD?

I guess that depends on height measurement scaling
(what distance range scales to 0 --> 10V) and what precision
you need

The slowest thing in your setup is the RS485 interface, everything else is much faster.

tommylight wrote: The slowest thing in your setup is the RS485 interface, everything else is much faster.

i change the head no more rs485
now i have RF cable for capacitance measuring,, and i make capacitance to frequency converter to be connected directly to mesa encoder pin,, similar to THCAD but convert the capacitance to frequency
500khz to 5mhz i will squeeze the fpga performance

PCW wrote: I guess that depends on height measurement scaling
(what distance range scales to 0 --> 10V) and what precision
you need

about 5cm will be scaled 0-10, precision the maximum i can reach with this setup.. i just want to keep up with head high while cutting at 27m/min

also encoder cable will be 15m+-,,, whats the suggestion for this