What's new
What's new

general ? on oscilloscopes

dsergison

Diamond
Joined
Oct 23, 2003
Location
East Peoria, IL, USA
I have a Tree J325 manual that describes using an oscilloscope to tune the servo drives yearly.

-and they may need looked at, i bought the machine used, and have not done it in the three years I've owned it although i dont put many hours on it.

is a usb oscilloscope a decent option? they seem inexpensive.

what is a good "general use" inexpensive scope?

I have zero experience with electronics in general but I can read and learn.

Thanks, Dan
 
I looked into this also knowing nothing about oscilloscopes. I wanted to tune the servos on my hurco. An electrical engineer friend that the usb ones (common as dirt on ebay) can only handle low voltages and a couple of amps and trying to use one for this purpose would likely fry it.
 
Most anything Tektronix on ebay is the best bet, the LCD ones are nice light and portable but they are still very pricey.
The USB ones mentioned may be a USB capture unit that turns a PC into a scope, and they work very well for low frequency, but they are essentially a storage scope as they capture and display, but they do not display in real time like a regular like Tektronix etc, Which can be a bit of a pain if you are trying to tune a wave form.
The one nice feature of the USB port type is if you are looking for a very infrequent noise etc, they can be set to only capture on a certain spike level say, so nothing happens until the noise or spike etc appears, then it is stored and can be retrieved at a later time.
M.
 
I have an old Tek 500 series scope that works fine for this. Your not talking about a very fast signal. Just looking for bounce in the output.
 
minder, do you know what kind of bandwidth would be needed for this? I've been wanting to get an oscilloscope for this purpose for a while but I know absolutely nothing about them! I'm assuming it's going to be a low frequency and a high bandwidth scope is unnecessary? My service documents say that you're just looking for a smooth waveform, so does that mean that any old scope will do? Sorry for all the questions, I'm kinda taking advantage while I've found someone who knows their stuff!
 
You can probabally get away without anything exotic, probally 10mhz would cover all you want to do, although if you are going the 2nd hand route, you probabally are not going to pay much more for a <=20 mhz, which is considered a minimum by many.
M.
 
the usb ones like Picoscope are ok for rough and ready stuff like i do, but a friend of mine uses a tectronics beastie that has a flat LCD screen which is of reasonable resolution, a 10 MHz general scope over here is about $140, Fluke do a handheld which looks good as it doubles as a multimeter
 
If the drives are three phase drives a scope with "line sync" is a lot handier. The handheld LCD scopes like a Fluke won't have that. No slur on the Fluke, I have one and love it but I always used an old Tek on drives.
 
You'll need a storage or digital scope for tuning drives. You need to see the response to a step input and on a regular ole scope the waveform will be gone before you can read it. Frequency response isn't really and issue as you be lucky to get a machine tool servo to respond at 500Hz. Cheapo PC addon scopes may be limited to +/-10 volts or may share a ground with the PC so a servo drive might fry your PC (make sure the inputs are isolated and check allowed input voltage). I use and old CRT style Tek.
Bob
 
At low frequencies there is no problem making a voltage divider to feed a +/-10 input. Probably requires no compensating capacitor.

To solve the common mode voltage problem use a differential input and two dividers. You will need adjustment for balancing the dividers.

.
 
Dan (& others)

You'd seen my earlier post about servo tuning. My friend, an electronics engineer, who did the work used my ancient Advance 2000 scope, a 20 Mhz machine. He said actually the older machine with a CRT is better here because of the rel slower image fade. Still he also got similarly useful from his much newer scope.

All he was looking for was the persistence of the trace, the ghost, of the pulse as it zipped by each time an axis was moved. It was the shape of the pulse and particularly the overshoot spike that he watched for. His goal was to see a rel. smooth ramp-up and ramp-down and wanted to eliminate the spike. He could compare the pulse from a different axis for reference (though they are not identical) . After 10 minutes of tweaking the spike was gone & the troblesome axis was now well behaved. Problem solved.

Hope this helps.
 
<<<<<the ghost, of the pulse as it zipped by each time an axis was moved. It was the shape of the pulse and particularly the overshoot spike that he watched for.>>>>
I picked up one of the USB/PC two channel capture units to complement my Tektronix http://www.syscompdesign.com/oscilloscope.htm , and it is certainly usfull for this kind of capture, it can be set for pre or post sync display and the advantage, apart from what I previously mentioned, is that the resultant waveform can be viewed frozen when captured for analysis and stored if you wish for later comparison on the PC.
You can get them for around $100.00.
M.
 
For a long time, pre WWII, there have been short, medium, and long persistence phosphors for scopes. P1 is a green medium persistence. P4 a white phosphor fairly fast used in TVs. P7 is long, and P11 is short.

A digital scope can have infinite persistence.

I use both digital and standard CRT scopes. Each has their place.

.
 








 
Back
Top