CLK IN NI PXI 5922

Question

Hi,
I'm using a 5922 digitizer with clk input and i have a problem.
My problem is simple: I could not phase lock to the external reference clock.
My CLK IN signal is a -250 mv:+250 mv square signal at 2Mhz (from low frequency generator) (this signal match with the spec).
My ch 0 signal is a random signal according to the spec range.
When i use Ni-Scope Express in LabView, my parameters are :
-> Range 2V
-> Coupling AC
-> Offset 0
-> input impedance 50 Ohm
-> Probe attenuation 1
-> Bandwith 0
-> Sample rate 2M
-> Record length 1000
-> N samples
-> Trigger type Edge
-> trigger source External trig
-> slope Positive
-> Coupling DC
-> Ref position 0%
-> Level 0V
-> Max time 10s
-> Delay 0s
-> Reference clock source : clock in
My error is :
"DAQmx Error -200245 occured
Measurements : PLL could not phase lock to the external reference clock.
Make sure your reference clock is connected and that it is within the jitter and voltage spec...."
Dont care about external trigger, it work fine !
I'm also using a NI example : niScope EX external clocking (i was just changing sample clock timebase source & rate by ref clock source & rate) and it dont work too.
and there is no signal on CLK OUT at any time.
What can i do, i'm locked with this problem ?
Thanks !
Gendre Laurent
Stagiaire au service Détection à Thalès Alenia Space
E-mail : [email protected]

Answer 1

Hi,
For example 60 MHz / 32 = 1.875 MHz is a sampling frequency (into the 5922) and i really need to be synchronize with my external clock  (so, not in intern).
Im now investigate on an alternative clk in (1Mhz or 2Mhz)  and i try to fix some problems like "PLL was unlocked" when i use my new clk and an edge trigger or " this device does not support RIS", ...
Its a little fastidious cause of parameters i have to take care.
But the main important thing on my work is the voltage precision.
In 20 bits, i have an important difference between two values for the same voltage input (verified by a scope) -> approx. 30 mV.
For a 0 : +250 mV signal with a 1 mV noise, its annoying !
Maybe, the antialiasing filter into the card is a problem for my measure.
Thanks for helping me, its not simple to drive this card for what i want !
ps : tomorrow i will post my VI.
Gendre Laurent
Stagiaire au service Détection à Thalès Alenia Space
E-mail : [email protected]