Some help if I may. Others can put their two bobs worth in as well.

Have I cooked my silly scope somehow?

It did work, if you remember. But on plugging it in this time, I get a constant ~ 2.2V on each channel. No probes connected. Note the amplitude.~0.

Dunno why.

Next, If I touch (finger) a channel pin/probe I get a 50hz oscillation with an amplitude of ~ 2.2V Get the same if I touch the channel 2 pin as well.

Finger on channel 1 probe/pin only.

I have tried a range of laptops and desktop. Changed the USB cable and ports. No diff

NB: On laptops, I **don’t ** get the 50hz oscillation if I unplug the power supply and run on battery when touching the channel pin. But still get the ~ 2.2V reading on both channels.

Next: I had soldered a new row of pins onto the board of the original, to mount it in a box with BNC plugs for proper probes..

Next. So I went and got another one, thinking I’d cooked the original one.. https://www.wiltronics.com.au/product/8564/picpcb-scope-oscilloscope/

Circuit diagram here https://picaxe.com/docs/osc001_schematic.pdf

But nup. The new one does the same thing. On both channels. I didn’t test it BEFORE soldering the pins on. Carefully and minimally soldered the pins on.

The thing is powered via the USB port, and the scope software has a utility to check the USB power supply voltage of the USB port. This checks out OK and is within correct range of 4.5 – 5.5 V.

I can’t believe I’ve cooked TWO of them the same way, on BOTH channels.

This time, I’m trying to detect “noise” in the phase shift/voltage spikes of the 14V AC power supply to the track of the toots. Noise that can be caused by arcing of the motor brushes in the loco, or very tiny shorts caused by train wheels crossing track points.

I’m stumped. Other than get ANOTHER one, and test it BEFORE I solder the pins on.

I did connect it to a 9V battery, and got silly erratic readings, and if I hold the battery case, it goes berserk.

Any ideas?

With nothing connected, I should get a 0V reading on both channels?

wadda ya reckon, hey what but.

sibeen said:

rushes in

Have I missed anything?

Woodie said:

sibeen said:

rushes in

Have I missed anything?

:)

Woodie, can you first short out the CH1 and ground input together and see if that changes anything. If that hasn’t made any difference can you adjust R12 and see if that changes anything.

sibeen said:

Woodie said:

sibeen said:

rushes in

Have I missed anything?

:)

Woodie, can you first short out the CH1 and ground input together and see if that changes anything. If that hasn’t made any difference can you adjust R12 and see if that changes anything.

Adjust R12 with the inputs still shorted.

sibeen said:

sibeen said:

Woodie said:

:)

Woodie, can you first short out the CH1 and ground input together and see if that changes anything. If that hasn’t made any difference can you adjust R12 and see if that changes anything.

Adjust R12 with the inputs still shorted.

Looks like you can use the jumper J1 to do the shorting.

sibeen said:

Woodie said:

sibeen said:

rushes in

Have I missed anything?

:)

Woodie, can you first short out the CH1 and ground input together and see if that changes anything. If that hasn’t made any difference can you adjust R12 and see if that changes anything.

I checked closely with magnifying glass and multi meter to see if any soldered pins have a solder short. Nup. If I “finger” short across the channel and ground, I get the oscillation but at a much lower amplitude. I did short the channel pin and ground, but I forget what I got. I remember it didn’t change the ambient voltage reading. I did muck with the 2 pots on the board, but it made no difference. I’ll try both again.

Woodie said:

sibeen said:

Woodie said:

:)

Woodie, can you first short out the CH1 and ground input together and see if that changes anything. If that hasn’t made any difference can you adjust R12 and see if that changes anything.

I checked closely with magnifying glass and multi meter to see if any soldered pins have a solder short. Nup. If I “finger” short across the channel and ground, I get the oscillation but at a much lower amplitude. I did short the channel pin and ground, but I forget what I got. I remember it didn’t change the ambient voltage reading. I did muck with the 2 pots on the board, but it made no difference. I’ll try both again.

I want you to deliberately short them together. Use J1 to do that.

sibeen said:

Woodie said:

sibeen said:

:)

Woodie, can you first short out the CH1 and ground input together and see if that changes anything. If that hasn’t made any difference can you adjust R12 and see if that changes anything.

I checked closely with magnifying glass and multi meter to see if any soldered pins have a solder short. Nup. If I “finger” short across the channel and ground, I get the oscillation but at a much lower amplitude. I did short the channel pin and ground, but I forget what I got. I remember it didn’t change the ambient voltage reading. I did muck with the 2 pots on the board, but it made no difference. I’ll try both again.

I want you to deliberately short them together. Use J1 to do that.

The board comes with feely available software which will provide accurate up to date information via a micro USB cable (Not supplied).

It wouldn’t surprise me if the feely software was a bit on the wobbly side.

Okies. I’ve put a pair of food handling latex glove on to stop any interference from me.

I shorted Channel 1 to GND and it showed a -ve voltage. Adjusted R12 to move Channel 1 (red) to 0v.

I’ll do the same for channel 2? Adjust R13 I assume?

Woodie said:

Okies. I’ve put a pair of food handling latex glove on to stop any interference from me.

I shorted Channel 1 to GND and it showed a -ve voltage. Adjusted R12 to move Channel 1 (red) to 0v.

I’ll do the same for channel 2? Adjust R13 I assume?

Yep

sibeen said:

Woodie said:

sibeen said:

:)

Woodie, can you first short out the CH1 and ground input together and see if that changes anything. If that hasn’t made any difference can you adjust R12 and see if that changes anything.

I checked closely with magnifying glass and multi meter to see if any soldered pins have a solder short. Nup. If I “finger” short across the channel and ground, I get the oscillation but at a much lower amplitude. I did short the channel pin and ground, but I forget what I got. I remember it didn’t change the ambient voltage reading. I did muck with the 2 pots on the board, but it made no difference. I’ll try both again.

I want you to deliberately short them together. Use J1 to do that.

I’ve got female-female plugs using that multi coloured ribbon stuff (forget what it’s called) on the pins, and shorted channel 1 – gnd with a male to male pinned piece of the coloured ribbon stuff.

sibeen said:

Woodie said:

Okies. I’ve put a pair of food handling latex glove on to stop any interference from me.

I shorted Channel 1 to GND and it showed a -ve voltage. Adjusted R12 to move Channel 1 (red) to 0v.

I’ll do the same for channel 2? Adjust R13 I assume?

Yep

Okies. Channel 2 (blue) shorted and R13 adjusted to 0V. But look where channel 1 went when not shorted.

Woodie said:

sibeen said:

Woodie said:

Okies. I’ve put a pair of food handling latex glove on to stop any interference from me.

I shorted Channel 1 to GND and it showed a -ve voltage. Adjusted R12 to move Channel 1 (red) to 0v.

I’ll do the same for channel 2? Adjust R13 I assume?

Yep

Okies. Channel 2 (blue) shorted and R13 adjusted to 0V. But look where channel 1 went when not shorted.

Woodie said:

sibeen said:

Woodie said:

I checked closely with magnifying glass and multi meter to see if any soldered pins have a solder short. Nup. If I “finger” short across the channel and ground, I get the oscillation but at a much lower amplitude. I did short the channel pin and ground, but I forget what I got. I remember it didn’t change the ambient voltage reading. I did muck with the 2 pots on the board, but it made no difference. I’ll try both again.

I want you to deliberately short them together. Use J1 to do that.

I’ve got female-female plugs using that multi coloured ribbon stuff (forget what it’s called) on the pins, and shorted channel 1 – gnd with a male to male pinned piece of the coloured ribbon stuff.

I’ve always called it multi coloured ribbon cable :)

Should I adjust R12 & 13 to 0V when each channel is NOT shorted? And just ignore the 50hz stuff when I touch the probe/pins?

Woodie said:

Should I adjust R12 & 13 to 0V when each channel is NOT shorted? And just ignore the 50hz stuff when I touch the probe/pins?

Certainly ignore the 50Hz shit.

What happens when you adjust the vertical scale to 2V/div on channel 1?

sibeen said:

Woodie said:

Should I adjust R12 & 13 to 0V when each channel is NOT shorted? And just ignore the 50hz stuff when I touch the probe/pins?

Certainly ignore the 50Hz shit.

What happens when you adjust the vertical scale to 2V/div on channel 1?

The actual measurements are on the measurements window.

Adjusted to 2V div. Channel 1 (red). displays as it should.

Woodie said:

sibeen said:

Woodie said:

Should I adjust R12 & 13 to 0V when each channel is NOT shorted? And just ignore the 50hz stuff when I touch the probe/pins?

Certainly ignore the 50Hz shit.

What happens when you adjust the vertical scale to 2V/div on channel 1?

The actual measurements are on the measurements window.

Adjusted to 2V div. Channel 1 (red). displays as it should.

That’s with CH1 open and 2 shorted?

sibeen said:

Woodie said:

sibeen said:

Certainly ignore the 50Hz shit.

What happens when you adjust the vertical scale to 2V/div on channel 1?

The actual measurements are on the measurements window.

Adjusted to 2V div. Channel 1 (red). displays as it should.

That’s with CH1 open and 2 shorted?

yes.

I’ve adjust R12 & 13 to get both channels to 0V not shorted.

Woodie said:

I’ve adjust R12 & 13 to get both channels to 0V not shorted.

Ahh, you can adjust the position with the sliders. Can you try that on CH1 when it is open and see what happens.

Woodie said:

Woodie said:

I’ve adjust R12 & 13 to get both channels to 0V not shorted.

I’d try adjusting the position/Level slider. Adjust the pot for CH1 when it is shorted and then use the Position/Level slider and see what happens.

Woodie said:

Woodie said:

I’ve adjust R12 & 13 to get both channels to 0V not shorted.

And it stays perfectly stable when on “continuous” without a murmur.

Woodie said:

Woodie said:

I’ve adjust R12 & 13 to get both channels to 0V not shorted.

And it stays perfectly stable when on “continuous” without a murmur.

But I get this at 50 mv/div. I’ll adjust R 12/13 as close to 0v as I can get.

sibeen said:

Woodie said:

Woodie said:

I’ve adjust R12 & 13 to get both channels to 0V not shorted.

I’d try adjusting the position/Level slider. Adjust the pot for CH1 when it is shorted and then use the Position/Level slider and see what happens.

The “position” sliders just move it all up and down the window. The slider marker (on the left) is for 0V. (above is +ve, below is -ve) If you are working with, say, all +ve voltages, you’d move the slider to the bottom to get the whole oscillation on teh screen.

sibeen said:

That just moves the 0V line up and down the frame, and the channel readings accordingly relative to 0V.

ahhhh troubleshooting via messaging.

:-)

Woodie said:

sibeen said:

Woodie said:

I’d try adjusting the position/Level slider. Adjust the pot for CH1 when it is shorted and then use the Position/Level slider and see what happens.

The “position” sliders just move it all up and down the window. The slider marker (on the left) is for 0V. (above is +ve, below is -ve) If you are working with, say, all +ve voltages, you’d move the slider to the bottom to get the whole oscillation on teh screen.

I want to see if that offset adjustment on the screen also adjusts the readings on the measurement screen.

sibeen said:

Before

After

sibeen said:

Before

After

Woodie, can you go to continuous rather than single shot.

Channel 1& 2 both not shorted @ 50mv/div R12 & 13 adjusted to near zero as possible.

Note low/high/amplitude of the sample for each channel.

sibeen said:

Woodie, can you go to continuous rather than single shot.

Yep. What do you want to see? “persist”?

Woodie said:

Channel 1& 2 both not shorted @ 50mv/div R12 & 13 adjusted to near zero as possible.

Note low/high/amplitude of the sample for each channel.

Turn up the vertical to 1 volt. Is it then pretty flat?

sibeen said:

Woodie said:

Channel 1& 2 both not shorted @ 50mv/div R12 & 13 adjusted to near zero as possible.

Note low/high/amplitude of the sample for each channel.

Turn up the vertical to 1 volt. Is it then pretty flat?

yep. pretty flat. But shows amplitude of 98 mv at 1v/dv No amplitude at 2v/div

Woodie said:

sibeen said:

Woodie said:

Channel 1& 2 both not shorted @ 50mv/div R12 & 13 adjusted to near zero as possible.

Note low/high/amplitude of the sample for each channel.

Turn up the vertical to 1 volt. Is it then pretty flat?

yep. pretty flat. But shows amplitude of 98 mv at 1v/dv No amplitude at 2v/div

Looks like it’s working :)

You’re always going to get some noise, especially with these cheaper versions. Once you hook up to a signal most of that noise will go away.

sibeen said:

Woodie said:

sibeen said:

Turn up the vertical to 1 volt. Is it then pretty flat?

yep. pretty flat. But shows amplitude of 98 mv at 1v/dv No amplitude at 2v/div

Looks like it’s working :)

You’re always going to get some noise, especially with these cheaper versions. Once you hook up to a signal most of that noise will go away.

Yeah. Muckin’ with them pots, I can’t get an amplitude <98 mv when not shorted. But close enough to 0V on each channel. (+/- ~ 40mv @ 50 mv/div.

Tried a 9v battery and now get what I expect. A good flat reading of 5.9 V. I know it’s a flat battery.

You are a gentleman and a scholar, Mr Beeny Boy. Have a slab of Guinness.😁

I have no idea why it worked last time, (checking the strobing of the LED light), I’ve been using the “new” one for this setup, and the old one seems to function the same. I have no idea why I’d need to adjust those pots. There’s nothing in the instruction manual about them and how to “calibrate” the thing using those pots.

The main bother was me holding it and stuff, with fingers and giving that 50hz oscillation, and 2.4V nothing attached reading. I’ll try the pot adjustment on the old one. I now believe there was probably nothing wrong with the old one.

Brilliant. Taa.

I’ll test the 9v battery with the multimeter and see if I get the same readings.

generally you want it like below, reliable earth all the way from oscilloscope, or whatever that does equivalent (front-end dealing with the signal, not the computer and software)

in an old school oscilloscope if you were looking at low voltage noise or AC on a substantial DC you’d adjust the trace position back down to where you wanted it, centre it, bring it back on screen even, or if you didn’t need see the DC you just wanted to see the noise or AC you’d switch the probe input to AC, which would bring a capacitor series inline and filter the DC off