attaching probes for high frequency measurements
attaching probes for high frequency measurements
(OP)
I need to investigate some noise problems on a printed circuit board. I'm adding an RF receiver to a device that has a commutated motor - lots of high frequency noise. Any suggestions for the type of probe and the way to attach to different areas on the PCB? I'm interested in noise to 500 Mhz.





RE: attaching probes for high frequency measurements
You should start off using a 10:1 scope probe, but throw away the earth clip, dismantyle the probe and connect to the inner grounding ring. If that is still too noisy then go for a straight coax lead soldered to the pcb, with say 470R in series with the signal wire at the signal source end. This again makes a 10:1 (-ish) probe but with better common-mode performance.
After that you are going to have to buy a differential probe, but now you are probably talking about £1000+
This is not a trivial measurement problem.
RE: attaching probes for high frequency measurements
Oscilloscopes may not have enough dynamic range to isolate a interference problem, and scope probes being sensitive to the electric field may pickup too much noise to effectively isolate some problems.
RE: attaching probes for high frequency measurements
Thanks to the both of you.
RE: attaching probes for high frequency measurements
RE: attaching probes for high frequency measurements
RE: attaching probes for high frequency measurements
RE: attaching probes for high frequency measurements
People do this type of seeking all the time with metal (treasure) detectors, so I don’t really think you need a picture
RE: attaching probes for high frequency measurements
If you decide to use passive probes a
very handy thing to have around is
the Bendix connector. You can buy them
from Specialty Connector Company or from
Tektronix. It's a small, bulkhead-
mountable, metal socket that the probe
tip fits into and it's terminated with
a solder post. You can't get a more
secure or shorter connections to the probe.
I usually solder the body of the connector
directly to the ground plane.
I've used these with both passive and FET
probes on sub-nanosecond logic as well as
for RF measurements and they work extremely
well. They're also great for taking
measurements in electrically noisy environments.
It beats the heck out of using a coiled
up paper-clip.
Best regards,
csharp
RE: attaching probes for high frequency measurements
Thomas K.
http://www.emcrf.eng.br
ICQ#282786426