Ghost voltage

Thread Starter

Nathan Hale

Joined Oct 28, 2011
159
Hello All!! Hope you are having a great day.
In the circuit below, when I close the switch, the multi-meter reads 1.7 volts.
When I open the switch, it reads 1.104 volts ( as you can see in the picture)
Can you please tell me why it is 1.104 volts instead of 0 volts? Thank you for your replies.






upload_2019-8-20_12-40-25.png
 

Bordodynov

Joined May 20, 2015
2,776
Your program can produce such an amazing result for two reasons. The first reason may not be the ideal switch element. When switched off, the resistance may not be infinite (usually in simulators).
The second reason may be that the simulator has a conductivity (albeit very low) from each node to the ground.
 

Danko

Joined Nov 22, 2017
1,040
1. LED1 has capacitance and some voltage presents after S1 is OFF.
2. You need to place S1 in +wire, because now S1 serarates ground from right part of circuit.
It may affects on simulation accuracy.
 

Thread Starter

Nathan Hale

Joined Oct 28, 2011
159
hi Nathan,
I am assuming you are using an actual circuit, not a simulation.???

Is there a strong light falling on the LED.??
Try covering it with your hand.
E
I am simulating it in Multisim. No, there is no light falling on the LED even in the simulation. ( I believe you were trying to tell me that there is some voltage going in reverse from an extraneous light source shining down on the LED).
Ty
 

Thread Starter

Nathan Hale

Joined Oct 28, 2011
159
1. LED1 has capacitance and some voltage presents after S1 is OFF.
2. You need to place S1 in +wire, because now S1 serarates ground from right part of circuit.
It may affects on simulation accuracy.
Could you please retype part 2 of your answer? I dont understand it well. Thank you
 

Thread Starter

Nathan Hale

Joined Oct 28, 2011
159
Your program can produce such an amazing result for two reasons. The first reason may not be the ideal switch element. When switched off, the resistance may not be infinite (usually in simulators).
The second reason may be that the simulator has a conductivity (albeit very low) from each node to the ground.
I think you are correct. The switch did have a resistance of 100M ohms. I changed it to 1000000000M ohms and the voltage is now 2.4 milli volts across the LED. Thanks!
 
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