Electronics > Beginners
How does a micro hook connect to a oscilloscope probe?
PsychedelicBreakfast:
I'm awaiting the arrival of my Rigol DS1052E. One of the reasons I finally ordered an oscilloscope is that I need to debug a circuit. The problem is, the parts I need to connect the probe to are very high density - 0.5mm pitch TQFP.
My question is, will the Rigol's probe be able to latch onto the pins of such a high density part? My guess is that it won't be able to.
So I've been looking at "micro hooks" similar to
But then I can't quite figure out how does the micro hook attach to my scope's probe?
Before anyone asks, the PCB, unfortunately does not have any test pads. The traces that I'd like to debug also do not lead into any vias and are quite thin - about 10 mils.
I know I could tack a wire onto the leads, but I'm hoping to avoid that. I'd really rather attach my scope directly somehow.
amspire:
You are right. If you can somehow prop up the oscilloscope probes so they are not putting pressure on the clips, you can sort of make it work.
But you are probably better off making up some ultra-lightweight 100:1 probes. The DIY probe basically comprises of a 4.95K smd resistor (5K close enough) connected to a thin lightweight 50ohm coax terminating at the oscilloscope end via a 50 ohm resistor to ground.
You can get the push on plugs to match the test clips so at the front end of the probe, you have two short wires (signal and ground) with the plugs as the front of the probe.
5K impedance sounds pretty bad compared to a 10M standard probe, but the 10M probe has a capacitance of something like 15pF - an impedance of 100 ohms at 100MHz. The diy probe probably is over 5 times better then this and have much faster risetime then the Rigol probes.
Most digital can cope with a 5K resistive load, along with opamp outputs, supply's. There will be some point you have to go back to the Rigol probe.
Here are a couple of links for 20:1 probes, but the idea is the same:
http://www.sigcon.com/Pubs/straight/probes.htm
http://emcesd.com/1ghzprob.htm
http://koti.mbnet.fi/jahonen/Electronics/DIY%201k%20probe/
Richard.
amspire:
--- Quote from: BoredAtWork on October 07, 2011, 08:06:55 am ---Attaching a micro hook to a probe pretty much ruins the high-frequency response. Some vendors do have probes with micro hook accessories. And they usually also specify them for low frequencies only.
--- End quote ---
This is for a 50MHz oscilloscope, not a 1GHz scope.
I think the microhook will be fine.
Richard.
PsychedelicBreakfast:
The highest frequency in the system is just 62.5kHz. I feel like that really shouldn't be a problem with a microhook.
I'd DIY my own probe (I quite like DIY!) but the issue is that I don't have time. Secondly, I haven't even gotten the chance to use an oscilloscope outside of a lab yet!
I'd really prefer a micro hook but I'm dumbfounded by the pictures/drawings on how one manages to connect one to their test probe or oscilloscope.
Are there really no test probes made for the purpose of probing tiny dense smd components? I don't need a high frequency probe, just something that fits into the dense pins of today's ICs.
alm:
The big scope vendors have adapted their probes to modern components: Agilent Tek1 Tek2 Lecroy. These probes probably cost about the same as a cheap DSO scope. Most of the current development (eg. solder-down probe tips) is focused on active probes, which cost more than your car.
The cheap 'commodity' probe manufacturers still seem to pretend that through-hole is standard and that DIP is a fine pitch, since their grabbers can't even grab a DIP leg or 1/4W resistor properly. Not sure why this is, can't they copy a thirty year old Tek design instead of a fourty year old one?
At 60kHz, you shouldn't have any issues. A passive low-impedance probe like amspire suggests is a great idea, but way overkill at close to audio frequency. Be sure to keep the wire from the probe to the clip as short as possible, a few centimeters or so.
Navigation
[0] Message Index
[#] Next page
Go to full version