Click the "X1/X10" switch.
Ah! Thank you! 10 meg. Looks like I have a lot to learn...
You need the ground clip to reference the probe to your circuit. It clips into the shrouded slot near the handle.
You can also (or should be able to) slide off the shroud, exposing a coaxial tip, which can be used with high bandwidth / high precision test points as pictured above.
... that much I do understand though
- I was just wondering if there's any reason I can't wrap a wire round this outside co-ax connector (indeed revealed by removing the sheath) just for a once off test of the thing, or if the ground wires have component(s) in them like the co-ax side clearly does. Seems there shouldn't be a problem doing this.
I haven't yet plugged a probe in as I've not been confident enough. I think I will now though, and try something VERY simple.
The scope should have a "PROBE COMP" or squarewave output somewhere on the front panel. This is used to compensate your probe (search on that for info), and also serves as a reference to verify it's working. (You don't need a ground clip to measure this signal, because it's already grounded to the scope. Remember that the scope grounds are all common, and you cannot clip ground onto anything that's not also grounded!)
Thank you again! I was not aware of this tiny tab in a sea of buttons. My primary objective right now is to see if it works properly - because I have nothing plugged in I have not yet seen the trace deflected in the Y direction apart from with the manual adjustment buttons (which only mean the CRT works).
Anyone who wants to know what the faceplate looks like just Google image search PM3055. Or for the extra lazy...
https://www.google.co.uk/search?q=pm3055&safe=off&source=lnms&tbm=isch&sa=X&ved=0ahUKEwis55u1zPXSAhVlDMAKHU3vB-UQ_AUICSgC&biw=1440&bih=776... that little one on the left says "Cal 1.2V [squarewave sign*]" which must be the thing of which you speak. Just to be clear, I can plug a ground-less probe into the scope, and safely prod this tab to see a square wave on the CRT?
I'm trying to unravel that last sentence about grounding... does something special happen when I use this calibration tab? Or is it simply due to the scope itself being grounded?
The scope ground is obviously the wall/house ground, and lets just imagine I am testing another non-isolated device, also grounded - lets say to the very same power socket extension. The non-isolated component is common ground to the tab on the scope. Can I use a ground-less probe in this situation? If not why not? We would just be measuring relative to wall/house ground, rather than relative to whatever the ground probe would be connected to.
I am aware most of the devices I test WILL be isolated and I will need ground probes, however, just for a test, I'll try the calibration and once I'm sure it works I will continue my reading/watching about scopes and probes. Unfortunately the video stickied (while great and I will watch the whole thing) concentrates on older scopes which do not feature a digital "main time base" button etc.
I assume with your last sentence you're just telling me not to put current up the ground wire. Sounds sensible. But... 'you cannot clip ground onto anything that's not also grounded!'... really? Can't I just measure the difference between any two points on an isolated device like with a multimeter?
Cheers!
~Atheus
/edit: *why doesn't this forum have a square-wave sign? Is that TinyMCE you use for a text editor? You can definitely put extra buttons on TinyMCE. It'd have to be custom because there's no Unicode square wave. Two types of sine and a sawtooth but no square. Who knew.