View Full Version : Oscilloscope Probe Adjustment

Jay Kickliter
09-05-2011, 11:49 AM
I have a 10x probe mated to a scope my buddy gave me, and I can't get it adjusted right. You'll see what I mean in the photo. If the (brand new) probe's adjustment screw does't straighten the square wave, should I assume the square wave reference is off? I don't have a spare probe or a spare scope, so I'm in the dark here.

Also, anybody have experience/opinions on these LeCroy scopes?



09-05-2011, 01:18 PM
The calibration output isn't likely to be faulty. Try connecting the probe ground to the ground point provided.

LeCroy scopes have a good reputation. I've only ever used one of the top end ones, though, where I once worked.

Erik Friesen
09-05-2011, 02:08 PM
What kind of probes? I just got done setting a tyrosis probe, kept trying to adjust it on the two setscrews at the base, before I remembered I had to adjust it at the probe tip.

Tracy Allen
09-05-2011, 04:14 PM
I'll echo Leon's comment, connect the probe ground clip to the calibrator ground.

You could check the signal path without the probe by running a wire directly from the scope input over to the calibration lug.

The 9400 seems to be available pretty often on ebay for a good price, and it seems to be very capable. You do have the manual, right? It is available on the LeCroy site. I use the LeCroy 9374L, also purchased used.

09-06-2011, 08:52 AM
Scope probe x10 mode works by using both a resistive divider and a capacitive divider, So long as the capacitive divider is trimmed correctly at the probe end it should give a square sqaure wave. The fact you can't achieve this suggests the trimmer capacitor in the probe is too small to match the input capacitance of the scope... (Or possibly that the probe cable is too capacitive or too long - high quality probe cable has very low capacitance per unit length)

Jay Kickliter
09-06-2011, 09:43 AM
I found a plain BNC with alligators laying around and everyone is right, it was just the 10X probe. It's a tektronix. I'll go shopping for a better one. Thanks.