rigol calibration signal up the spout

[Simon]

Hi Guys, I struggle to get the calibration sinal from the scope so that I can calibrate probes, at first I thought it was the probes because if I pull the BNC plug about the waveform goes up and down in amplitude, hec I even spent 25 quid on a new set of probes but got the same thing, however whilst waiting for those new probes I took it to work and use the cal signal of another scope, and low and behold I had no problem, Anyone else got this ? I guess I'll just have to set up a 555 or a pic as a signal generator in future

[Mark_O]

I struggle to get the calibration sinal from the scope so that I can calibrate probes...

I thought it was the probes because if I pull the BNC plug about the waveform goes up and down in amplitude.

This makes no sense to me.    Would you like to try again, in English?  

Are you saying that if you clip your probe on the front-panel connectors, you don't get a ~1 kHz square wave at about 3Vpp?  If that's really the case, you must have shorted it out and fried the generator.

- Mark

[Simon]

thats what I'm saying yes I do not get the signal, I get a tiny signal mared by the scopes own noise because the signal is so small, if I pull the plug about I get flickers of the signal, nice and big, it jumps up and down in amplitude as I fiddle with the plug. it did infact behave exactly as if the socket was not grounding properly, but when i used the calibration signal from another scope at work it worked just fine.

surely if I had shorted the calibration output which I'm sure I have not done it would give me nothing at all ?

[Mark_O]

thats what I'm saying yes I do not get the signal, I get a tiny signal mared by the scopes own noise because the signal is so small

Well, that's not proper at all.

if I pull the plug about I get flickers of the signal, nice and big, it jumps up and down in amplitude as I fiddle with the plug.

When you say "plug", do you mean the BNC connectors on the probe inputs?  Those should be attached pretty solidly to the chassis.  I hope you don't mean that wiggling the BNC jacks has any effect at all on the signals that are displayed?  Or did you take it apart and remove the retaining nuts, and forget to put them back on securely?  

Or do you mean the Cal output fingers?  I really can't tell for sure what you're talking about.  I was just noticing from the pictures that Dynomo posted a short time ago, that the Cal outputs come though a slot in the metal chassis, and don't seem to have any insulation around them.  So if they were bent too far to the left or right, they'd short out against the chassis.  

surely if I had shorted the calibration output which I'm sure I have not done it would give me nothing at all ?

Not necessarily true.  You can short out a driver, and break down the junction, and have vastly reduced output voltage levels.  But then they wouldn't go back up again.  

- Mark

[Simon]

right: the sockets are firm thats not the issue I have only taken the back off not totally dismantled it.

if I wiggle the probes BNC jack it makes no difference if i am measuring an enternal source like off my finger of the other scopes cal generator. it only has an effect when I wiggle it whilst trying to measure the scopes own calibration signal output, thats the odd thing.

I think mybe your right the calibration signal generator is broken, maybe i shorted them with the earthing crocodile clip  so stupid of rigol to not offer some protection against that as it is very easily done.

I get nothing at all from it now

[Mark_O]

right: the sockets are firm thats not the issue I have only taken the back off not totally dismantled it.

Well, that's good news, at least.

if I wiggle the probes BNC jack it makes no difference if i am measuring an enternal source like off my finger of the other scopes cal generator. it only has an effect when I wiggle it whilst trying to measure the scopes own calibration signal output, thats the odd thing.

OK.  The only way that could happen is if while you're wiggling "the probe's BNC jack", the cable (or the ground clip) is moving around where you clipped the probe to the Cal output.  That's the only thing that makes any sense.

I think mybe your right the calibration signal generator is broken, maybe i shorted them with the earthing crocodile clip   so stupid of rigol to not offer some protection against that as it is very easily done.

That's certainly a possibility.  And if "it jumps up and down in amplitude as I fiddle with the plug", that means you were shorting it out, over and over again.  

I get nothing at all from it now

I'm sorry to hear that.

- Mark

[Simon]

oh well I'll probably make a 555 circuit to replace it