Measuring xtal frequency

D

DaveC

Guest
Xtal resonator (see my post elsewhere in this NG) input to custom
microcontroller is suspect. I'd like to view the frequency signal, but the
minute I put my scope probe on it everything halts, and only a DC voltage is
visible.

I'm presuming that the probe is loading down the circuit such that it stops
dead.

How can I successfully view this? Just find a better probe? Any other
interface tricks I can try?

No schematic or pin data on the microcontroller, so if there's a "clock out"
pin I can't find it...

Thanks,
--
Dave C.
dave-usenet3016@mailblocks.com
 
"DaveC" <dave-usenet3016@mailblocks.com> wrote in message
news:0001HW.BB637D340000C03603857670@news.individual.net...
Xtal resonator (see my post elsewhere in this NG) input to custom
microcontroller is suspect. I'd like to view the frequency signal, but the
minute I put my scope probe on it everything halts, and only a DC voltage
is
visible.
Click to expand...
A 10x probe may allow it to run, make sure you're on the output side.
I use a shortwave receiver with BFO, which also allows me to determine
frequency pretty accurately.
 
Begin by adding 100K-ohm resistance from your test point to your scope probe
tip. Gradually increase to 2M or 4.7M or so. If is probe loading that
should prove it. Also, don't use the ground clip on your probe. Short the
ground collar on the probe tip to a nearby ground with a "greenie"
screwdriver or other short metal object. The direct ground makes a big
difference.

Good luck!

Len G.


"Dave VanHorn" <dvanhorn@cedar.net> wrote in message
news:w3idnY7sKZN4xaOiU-KYvw@comcast.com...
"DaveC" <dave-usenet3016@mailblocks.com> wrote in message
news:0001HW.BB637D340000C03603857670@news.individual.net...
Xtal resonator (see my post elsewhere in this NG) input to custom
microcontroller is suspect. I'd like to view the frequency signal, but
the
minute I put my scope probe on it everything halts, and only a DC
voltage
is
visible.

A 10x probe may allow it to run, make sure you're on the output side.
I use a shortwave receiver with BFO, which also allows me to determine
frequency pretty accurately.
Click to expand...
 
Sorry. I didn't mean to do that!

Begin by adding 100K-ohm resistance from your test point to your scope probe
tip. Gradually increase to 2M or 4.7M or so. If is probe loading that
should prove it. Also, don't use the ground clip on your probe. Short the
ground collar on the probe tip to a nearby ground with a "greenie"
screwdriver or other short metal object. The direct ground makes a big
difference.

Good luck!

Len G.

"DaveC" <dave-usenet3016@mailblocks.com> wrote in message
news:0001HW.BB637D340000C03603857670@news.individual.net...
Xtal resonator (see my post elsewhere in this NG) input to custom
microcontroller is suspect. I'd like to view the frequency signal, but the
minute I put my scope probe on it everything halts, and only a DC voltage
is
visible.

I'm presuming that the probe is loading down the circuit such that it
stops
dead.

How can I successfully view this? Just find a better probe? Any other
interface tricks I can try?

No schematic or pin data on the microcontroller, so if there's a "clock
out"
pin I can't find it...

Thanks,
--
Dave C.
dave-usenet3016@mailblocks.com
Click to expand...
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top