Where do I place my measuring devices on my circuit?

Thread Starter

Ashley1nOnly95

Joined Feb 7, 2017
11
This might be a silly question. But, I wanted to know where do I place my measuring devices on my circuit? How do I know that I am measuring what I want to be measured. I know that my negative pin(it's not a pin but it's what I call it) on my oscilloscope (using multisim) should always be grounded because I need to measure against zero. If I measured against anything else with a signal I wouldn't know what the measured signal is. But I'm having problems knowing where on the circuit to place my positive pin.

Is there a rule as to how you know where you need to place your pins in order to get the correct measurement output?
 

ScottWang

Joined Aug 23, 2012
6,874
Please show any of your schematic, and describe what your trying to messure, it is more practical to answer your question.
 

Thread Starter

Ashley1nOnly95

Joined Feb 7, 2017
11
upload_2017-2-11_2-55-7.png
I want to measure the output of the transformer and the resulting signal.
For the transformer right before 150 resistor and for the resulting signal after the capacitor.
 

ScottWang

Joined Aug 23, 2012
6,874
The ground of mains as AC115V in the pdf file was wrong, you can't connected the AC115V(-) to Gnd and the 0V of AC6.3V to Gnd at the same time, although probably it won't damage anything, but it will make the transformer become non-isolated, and it will also bring the risk to damage anything in the real world, specially the lower voltage side.

So the first thing is to disconnect the negative(-) pin of the mains(AC115V) from the ground.

If you want to measure the diode then you can connect as this:
Channel zero.
Ch-0(+) → (+) diode (-) → Ch-0(-)

If you want to measure the output voltage(Voltage cross on R1) then you can connect as this:
Channel one.
Ch-1(+) → (+) R1 (-) → Ch-1(-)
 

Thread Starter

Ashley1nOnly95

Joined Feb 7, 2017
11
So I have channel zero measuring the output of the transformer and then I have channel zero measuring the output after the diode. But it still does not work.
 

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ScottWang

Joined Aug 23, 2012
6,874
Please post the jpg file, many of our members don't like to read the pdf file.
Your wiring was wrong, please recheck my posted, specially the GND of O'scope.
 

Thread Starter

Ashley1nOnly95

Joined Feb 7, 2017
11
Can you clarify what you mean by

Ch-0(+) → (+) diode (-) → Ch-0(-)
Channel zero positive to after the cathode on the diode.
Channel zero negative to ground
Ch-1(+) → (+) R1 (-) → Ch-1(-)
Channel 1 positive to connection after cathode diode(area between diode and resistor)
Channel 1 negative to ground.
 

ScottWang

Joined Aug 23, 2012
6,874
Please just don't think too complicated, it is very clear to showed you the wiring.

This is the way to measures the voltage cross on diode, but it can't be measures the Ch-1 at the same time. (I'm not sure to use this method on software that the Negative(-) of O'scope will also connected automatically to Gnd or not)
Ch-0(+) → (+) diode (-) → Ch-0(-)
Channel 0(zero) :
The positive(+) connects to the Anode(+) of the diode, Negative(-) connects to the Cathode(-) of the diode.

Ch-1(+) → (+) R1 (-) → Ch-1(-)
Channel 1(one) :
The positive(+) connects to the positive of R1 (or the Cathode(-) of diode), the negative(-) connects to the negative of R1 or Gnd.

The Ch-o and Ch-1 are according to your pdf file, we already used them as ch-1 and ch-2 in the real world.

If you wan to measure the 6.3Vac then you just cross the 6.3V and 0V(or Gnd)
Ch-0(+) → 6.3Vac secondary side 0V → Ch-0(-)
Channel 0(zero) :
The positive(+) connects to the 6.3Vac, Negative(-) connects to the 0V(or Gnd).
 
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