Multisim and Ultiboard

cancel
Showing results for 
Search instead for 
Did you mean: 

Multisim shows wrong voltage in voltage divider?

Just downloaded Multisim.  

 

Used it years ago.  Made a simple resistor network and measured voltages across the resistors.

 

If the power source is a battery 12v, and there are 3 resistors, 2k, 2k, 1k and I measure across the middle 2k resistor, what should the voltage be?

 

it measures 12v.

 

So a battery source, and 3 resistors in series.  am I doing something wrong?  why does it show 12v?  across the middle resistor?

 

https://www.grc.nasa.gov/www/k-12/airplane/ohmrser.html

0 Kudos
Message 1 of 5
(137 Views)

The initial schematic was drawn where the battery negative went to the GND symbol, the battery pos went to the first  of 3 series resistors, the last resistor went to another GND symbol.  this produced wrong results.

 

Then I removed the GND references and connected the wires with just a battery and 3 resistors.  here it gave the right voltage across the 2nd resistor

 

Added the GND references.  it has the same reading.  Most of my work for the past 20 years has been writing and testing software and applications;  I double and triple checked the setup, it failed as noted.

0 Kudos
Message 2 of 5
(103 Views)

MonicaIgnat_0-1622629261543.png

Hello,

Can you provide more details about what kind of measurement are you performing?

In order to obtain the voltage across the R2 (middle) resistor, a differential voltage probe can be used.

As computed in the link you have sent, the voltage value across R2 resistor is correct.

Thank you

 

0 Kudos
Message 3 of 5
(73 Views)

ok the 4th time trying to reply here...  ni is not what it used to be.

 

your sch has 3 resistors in series with 1 battery and 1 gnd reference.

 

i started with the battery, neg post to gnd. 

3 resistors, one tied to batt POS, the other end of the 3 to another gnd.

 

measurements were wrong.

 

Then added 7400 ttl nand gate, dropped 3 gates, added a transistor, measured the gates, one of them had the output 1.5v ???  it was connected to an input of another 7400.  in ttl the output of this device is never 1.5v its not possible unless its defective.  .2 ish for a low and 3.8v or higher for a 1

 

later without changing the wiring that same line measured 5.0v on the meter

 

In a few minutes of connecting things, the measured voltages were wrong, and they changed.  

 

not as much detail because having to type it all out again isnt fun.  will click and probably say cant find text, mismatch try again later.

0 Kudos
Message 4 of 5
(64 Views)

MonicaIgnat_0-1622710629475.png

We cannot reproduce the behavior described with two ground connections.

What instruments did you use to measure the voltage?

What type of simulation have you chosen?

Can you provide a screenshot of the schematic?

Thank you

0 Kudos
Message 5 of 5
(50 Views)