how can i measure the ripple (noise) of a power supply with PXI 6133 and a 10:1 Probe

[tymark]

I have a PXI 1033 chassis and PXI 6133 with TB2709 adaptor... i must measure the ripple on the output of a power supply with T2220 probe from Tektronix....

PXI 6133 don`t let me to put AC coupling, just dc coupling...

It is possibly to measure the ripple with my configuration???? can anyone help me?!

Thanks a lot!

[R Sandoval]

Hello Tymark,

What kind of frequencies are you expecting to measure?  Just so you know, the PXI-6133 contains internal hardware filters to reject 50/60Hz noise that may impact your signal acquisition.  However, digitizing the signal in a high rate will permit you to render the signal with minimal distortions.  Also, please be careful with the voltages that you are measuring and make sure you do not go over the limit of the card (35V active, 25V off).  More information about the PXI-6133 can be located at:

http://www.ni.com/pdf/manuals/371231d.pdf

In regard to your setup, I was unable to locate further information about the Tektronix T2220 probe.  You may want to refer to the manual to see the limitations of that probe.  Nevertheless, the setup is fairly straightforward.  The T2220 should be connected to a common ground and line of the signal you wish to observe.  You can use a test panel in Measurement and Automation Explorer for the signal acquisition.

[Henrik_Volkers]

You can use a capacitor to cut off the DC , BUT if you connect the the probe a high voltage peak will pass the cap.

So assuming you have a higher voltage I would think about 2 high voltage rated capacitors in series followed by a a voltage divider (500k/100k) to limit current for the protection circuit.

The 100k together with the internal 100k impedance will build a 10:1 divider with the 500k and you will need a 2pF compensation in parallel to the 500k due to the 10pF of the PXI6133  (twist two teflon isolated wires and cut them down until you get a nice rectangle with a square excitation). 

DISCLAIMER: The PXI 6133 note in the manual :

Caution Do not use for measurements within
Categories II, III, and IV.

So, if you are in doubt get in contact to your local NI ....

[tymark]

Thank you for your time and advice.....I want measure the ripple on a 24 V power supply and i use a probe from tektronix P2220   200MHz, 10M, 16pF, 300V CAT II, 10:1 or the same probe but i can change the range to 1:1, 6MHz, 1M, 95pF, 150 V CAT II.

I will use 2 capacitors in series : 63V / 1000uF and i will set the probe range to 1:1..The peak to peak value of the ripple must be under 300mV...

Thanks again,

Tudor Nicoara

[Henrik_Volkers]

Make shure your tek probe fit to your input impedance. Usually scope inputs are about 1M,30pF or 50R,15pF(?)  your device is 100k,10pF.  Or is it an active probe??

And don't use electrolytic or tantal caps, usually to much leakage. 10µF Film capacitors should do the job.

To high end: Have a look at Jim Williams appnote to Voltage reference noise measurements at linear.com 😉

[tymark]

Yuhuuu...it`s works....thanks a lot...first with 10 uF until the signal offset is 0 i must wait 60 s and i decided to put just 5 uF and the time until the signal offset is 0 it`s above 35 s...The signal amplitude is`s the same in both cases...

Thank you so much,

Tudor