Test Equipment: Oscillocopes

[TinselKoala]

OK, so we have the issues relating to the calibration trace sorted, then, I hope. Nothing is wrong, it's normal behaviour when looking at the Calibrator signal with a 1x probe and AC-coupled input. The probe compensation should be adjusted with the probe in the 10x position, and normally you will be using 10x probe setting and DC-coupled inputs in most cases anyway.


You do realize that you will void your factory warranty by using that "blaster" stuff on your scope, I hope....   

Seriously... I don't think that any form of petroleum solvent is a good idea to use. Who knows what kind of residue they  might leave behind, or what they might dissolve in there. Stick with the commercial contact cleaners specifically made for the purpose. That's just my two cents worth.


As far as the probes go... No, none of these aftermarket probes that are "inexpensive" have the hardware for the scope to detect the attenuation setting. You may note on the actual Tek probe you have that there is a little pin next to the BNC connector. This is the "readout pin" that makes contact with a ring around the base of the BNC connector on the scope chassis, and this is what tells the scope what attenuation setting you have on the probe, according to the switch setting on the probe.

When using a probe that does not have the readout pin and its internal wiring, you just have to remember the atten setting and look at the right number on the V/div scale. That is, you use the knob value that is over the "10x" or "1x" indicator light, appropriately.

Most of the time you will be using 10x attenuation anyway. When you use a 100x probe then you need to multiply the 10x indication by 10 again.

[Brian516]

Ah ok, good to know.  I didn't realize that the little pin is what tells the scope to switch the light from 1X to 10X.  That is really all it's doing on this scope, correct?

I just did a little experiment with a few slider pots that I had from an old stereo, and noticed that even the high quality Deoxit doesn't actually "remove" really any of the gunk from it, and only removes a very small amount when it is "flushed" after a min or so. When I loosened the gunk up with Deoxit, and then put a little PB on it, the gunk immediately came off when I blotted it with a paper towel. Afterwards, it appears the IPA rinse removed all of the PB and Deoxit and left the slider nice and clean, and functioning way, way, way better than the "control" slider and also the Deoxit slider both with and without rinsing.

HAHAHA Factory warranty.... I WISH!  If only, if only............ 

What then about your comment regarding the use of WD40 on badly oxidized/dirty switch contacts before? Both PB and WD have the same petroleum distillate as their main ingredient.  However, I guess there is a bit of a difference between using it on an exposed and easily accessible part and an enclosed pot... I really do not want to be taking the back cover off of each of these pots to clean them out. who knows if I would ever get them back together if there's a spring in there that decides to shoot all the parts out in my face.. 
I guess if this D5 just isn't cutting it, I should try and locate some kind of better contact cleaner. The manual does specifically say not to use petroleum ether products to clean anything. I guess I'll just have to try Grainger for some aerospace contact cleaner, or order something. What would you suggest?
I still think it may be a good idea to rinse the pots out afterwards with IPA, what do you think?
Never mind, It seems the more I work the knob back and forth, the less "noise" I get. I'll just sit here and change the settings repeatedly for a while until it's no longer noticeable!

It's mainly the CH2 coupling switch under the V/DIV knob giving me trouble still, but it's also the position knob. All the other knobs/switches seem to be working fine now.

Also I just want to add that I definitely needed to adjust the tuning capacitor on the probe when I moved it from CH1 to CH2, so, like you stated, it is definitely necessary to adjust them when moving them from one channel to another, at least on my scope.

On another note, for the Arduino LCD I remember you saying that the Parallax one is the best because it only takes up a few spaces on the duino's output.  Well, I think I've found out how to make that with a generic LCD and an I2C chip. Check this out and let me know if you think it's a good way to go.
http://electronics-diy.com/two-wire-i2c-arduino-lcd-display.php

Brian

[TinselKoala]

Yes, the readout pin just tells the scope to switch the indicator light. It doesn't do anything else in the scope.

No, that wasn't me who suggested the WD-40 before, I think it was Pirate. If it works, great. If it screws up your pots and switches... then what are you gonna do?
Just don't get any on those special attenuator boards, the SM specifically warns against that.

Yes, the Parallax LCD has some kind of serial interface wired in to give it the 1-data-line capability. There is an Arduino library of function calls for the Parallax LCD using its interface. I don't know if this will also work with your chip+generic LCD. You may have to write your own library functions for it! There are many libraries for the various LCD types, see the "playground" link below.

Ah... I see that the link you provided has already taken care of the necessary I2C libraries, that's great! The I2C uses 2 wires and the Parallax only one, but sure, it seems like a good project to try. Probably a lot cheaper than the Parallax LCD too. But no speaker.

http://arduino.cc/en/Reference/LiquidCrystal?from=Tutorial.LCDLibrary
http://playground.arduino.cc/Code/LCD   (scroll down for the Parallax 3-wire LCD library)

[Pirate88179]

I don't think it was me suggesting WD-40 for the pots on a scope.  I used that trick suggested by AllAmerican5 Radio (Youtube) for treating the pot on my old Triplett meter but I don't think I would risk that on anything inside my scope.  It does sound like something I might suggest though.

Bill

[Brian516]

[quote author=TinselKoala link=topic=15536.msg440014#msg440014 date=1424911163
Ah... I see that the link you provided has already taken care of the necessary I2C libraries, that's great! The I2C uses 2 wires and the Parallax only one, but sure, it seems like a good project to try. Probably a lot cheaper than the Parallax LCD too. But no speaker.

http://arduino.cc/en/Reference/LiquidCrystal?from=Tutorial.LCDLibrary
http://playground.arduino.cc/Code/LCD   (scroll down for the Parallax 3-wire LCD library)
[/quote]

I didn't know the 3-wire had a speaker as well.  Oh well, the 4-wire generic will have to do for now. Once I know what else to get from Digikey or one of the others I'll grab up one or two of those chips.  I'd get the Parallax, but I can think of quite a few other things that I'd rather put $40 towards, like a good power supply, a FG, Variac.....
I dug out my old vid cam earlier and found a mount for a tripod, so now all I need to do is find the cable to connect it to the PC and get or make a tripod, and I'll be able to stop nauseating people with my shaky vids