What scope should the plant electrician buy?

[HJTRBO]

Hi all,

After starting a new job and convincing management of the need for a scope they have so generously allowed a poultry AU$700 to play with.

... I must say that there are so many models in the lower end of the range that it is becoming quite a task to finally settle on a choice of scope.

This is where you guy's come in!

My primary purpose for this unit is to measure quadrature encoders, resolvers, and indexing signals for fault finding purposes. I have a preference to units that are portable (i.e handheld digital type), available from an Australian distributor (warranty and service support) and PC connectivity a welcome luxury but not a necescity).

I have stumbled on many E-Bay item's, one of which in particular the Uni-T UT81B. 8MHz, good out of box accessories, wide range of functions.

I would appreciate any personal recomendations from you for oscilloscope unit's that are within budget (AU$700) and able to perform the low level tasks outstandingly well that I will ask of this tool.

I really appreciate your recommendations.

 

[bernie_carlton]

allowed a poultry AU$700 to play with

Why - that's chicken feed!

 

[TimWilborne]

Not that I'm trying to discourage the purchase of a scope, I love toys!

But do you really need a scope to test encoders and resolvers? I used to work quite a bit with them and I can't say that I ever recall one "acting erratically" if properly installed. For an encoder usually either a channel went out(grit) or we would break a soldier joint from excess movement. While a scope would have been nice to troubleshoot with, the LEDs on the controller will tell you the same thing. If it doesn't have LEDs you can connect one where you would put your scope and tell the same thing for tremendously less money.

As far as resolvers I can't say I have ever seen one go electrically bad. We used to have them on large presses and the impact would break their mounting tabs in the back of the encoder and destroy them. Other than that they are virtually unbreakable. Still seeing an LED flicker would make me 99.9% sure nothing is wrong with the resolver

 

[HJTRBO]

TWControls; LED, I like it! Why I never thought of that myself, I.Q. 114 maybe explains it.

 

[Steve Etter]

I can't say that I ever recall one "acting erratically" if properly installed.

This is one of the two reasons why I have been very glad to have a scope - to demonstrate the problem exists AFTER the crude installation process but not BEFORE.

The other reason is for identifying noise. Sure, I know this comes back again to proper installation, but now it's Black Majic stuff, not mechanical stuff.

By the way, I did have one "acting erratically" situation that I never did figure out. We had a machine with 5 encoders all within a few feet of each other (mounted on driven rollers for a common wind/unwind process). On one of the rollers, whatever encoder was mounted to it, we would lose pulses. Change the encoder with another from a roller next to it, and that encoder would stop losing pulses. Ran new cabling - all out in the open so no nearby noise sources - no change. Used the new cabling on nearby roller/encoder - no problem. In short, everything we did pointed to the encoder itself mounted on that roll was the problem. Finally, the only solution we found was to change brands of encoders. I have no idea why this worked, but it did.

Sorry for the long winded story....old guys, I guess.

Steve

 

[keesoon]

do you conect the encoders to what a PLC?
is an AB
AB softwares got A trend so you can see like a scope in sofware

 

[HJTRBO]

Thanks for the input guy's.

I to have had an erratic old fashion binary encoder play up on the 8^2 channel.

THe need to self educate also requires the need for such a tool.

And thirdly we have many indexing machines with solid state logic so it's important to monitor certain signals to try to convince the mechanical guys it's not electrical.

 

[HJTRBO]

UPDATE:

I ended up grabbing the UNI-T 81B off ebay. AU$260 delivered. Had it for a month and it's already on a second set of double A's.

So far so good. No problems with encoders and has become very handy for analogue signals. Good accessories (alligator clips, BNC adaptor, USB cable, leads, but no BNC probe) PC software, data logging and also functions as a digital multimeter.

Bad points: Doesn't have that chunky robust feel, counting divisions with your screw driver to determine what frequency and voltage you have, and autoranging is slower than your mumma...

Overall, as the title suggests it's a scope for the plant electrician, NOT the process or electronic engineer! Should I get two or so years out of it i'll be buying another one.

Hope this helps some people out there.

 

[mordred]

I've always enjoyed the fluke scopemeter but its pricier been using it for years although seldom on encoder and resolvers