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Looking for PS glitch with Tek scope?

I have a machine in that I suspect the PS (+24vdc) is sagging under load which is causing all kind of havoc with the digital circuits. The load is brief, so I've not been able to capture it with a DMM.

I borrowed a Tek TDS410 digitizing scope. It's quite complex (to me, anyway) and I'm not sure how to view the PS such that I can capture a sagging output.

I've used a 465 decades ago and a 2467 more recently, but the digitizing scopes are new to me.

There's all kinds of capture modes (sample; peak detect; envelope; average), measurement modes (high; low; max; min; 16 others), and trigger modes (auto; normal; rising edge; falling edge).

I presume that I set the trigger just below the output voltage (ie, 11.80v), falling edge, and activate the load. Beyond that, it's a mystery to me.

The site is a bit of a drive, so I've been practicing in my shop with a stand-alone PS.

I've looked on-line for an operator's guide, but all I've been able to find is a service manual (TDS410/420/460) which has not much in the way of setup and operation.

Any suggestions regarding the best combination of features to use for this simple task would be most appreciated.

Thanks. GW

Reply to
Gary Walters
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Top of the control panel to the right of the display is the 'General Purpose' knob. Just to it's right is a button labeled 'Autoset'. Hang your probe on the power supply and press the 'Autoset' button. Your scope will now be initialized at a good starting point. From there, adjust trigger polarity and level, 'sweep' speed, memory depth. Bob's your uncle.

If you get into a puzzling situation where you can't see the trace or can't get the scope to trigger, just pop the 'Autoset' button again and you will be getting good data in no time.

I really like the Tek TDS series. Clearly the user interface was designed by an actual scope user rather than just a software (Cough Agilent cough) engineer.

--Winston

Reply to
Winston

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Put it in sample mode and forget the rest for now. Make sure the input is set to DC couple.

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Can you trigger on whatever is causing the brief load? This would make your life easier. If not then as you say set the trigger level just below the voltage level before the load is activated. If you first put the scope in auto trigger you will see the DC level. Set the trigger level just below this and change the triggering to normal (or maybe single shot) You'll want to trigger on the falling edge. Now all you have to do is set the time base.. probably you'll have to play around with different time bases since you don't know how long the voltage sag lasts.

You can use the DC offset knob and Volts/div knob to zoom in on the transient behavior.

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Good luck,

George H.

(PS I hate the autoset button, I wish I could tape mine over. Every once in a while I hit it by accident and then curse.)

Reply to
George Herold

Which Agilent scopes are you referring to? I like the 548XX Infiniium series...

Reply to
JW

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Can't recall the model number. It was a fancy 4 - channel color DSO. Looked very similar to:

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I found the user interface counter - intuitive because some of the controls wouldn't do their function apparent from the labeling. It was sort of "You can't get there from here."

Perhaps they have improved greatly in the intervening 16 years. I certainly hope so.

Have you used a TDS? Those are really nice. A very easy migration to digital storage technology for those of us that started with tube - type 'recurrent sweep' scopes. Even the 'help' system was easy to understand and actually had helpful information.

--Winston

Reply to
Winston

Yeah, that model is similar to the one I was talking about. Mine is a

54845A - a bit less capable. I like that series, but it may be due to it's PC interface and pull-down menus. I've gotten so used to PC interfaces I actually use the mouse to control the scope more than the actual front panel.

The latest model I've used is the TDS7XX series. I like them as well, but would still take the Agilent over it any day.

My first scope at work was a Tek 465, then a 2465B. Even had a 434A analog storage type at home. But once you go digital, you never go back. At least with me, anyway. :) Many die-hards would think of me as a blasphemer, I suppose.

Reply to
JW

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