1
\$\begingroup\$

I am supposed to be doing an online engineering assignment and was in the midst of simulating some circuits in Multisim when I noticed something. The placement of the ammeter before and after the resistor yields different values Picture 1: Ammeter before resistor Picture 1: Ammeter before resistor Picture 2: Ammeter after resistor Picture 2: Ammeter after resistor

Also, I noticed that the placement/presence of the ammeter also affects the reading of the multimeter XMM1 Picture 3: Multimeter reading without ammeter present Picture 3: Multimeter reading without ammeter present Picture 4: Multimeter reading with ammeter after resistor Picture 4: Multimeter reading with ammeter after resistor Picture 5: Multimeter reading with ammeter before resistor Picture 5: Multimeter reading with ammeter before resistor

What could be the reasons for the current and voltage? This is a dumb question, but I thought that theoretically speaking, the current flowing into and out of a resistor should be the same and that an ideal ammeter should not affect the current whatsoever? Could it be that I connected the components wrongly or is this some quirk of multisim? Thank you for any answers in advance.

\$\endgroup\$
5
  • 1
    \$\begingroup\$ That's really strange, the current loop is the same they should have the same reading \$\endgroup\$
    – Lorenzo Marcantonio
    Commented Oct 19, 2021 at 7:39
  • \$\begingroup\$ in the first two diagrams, the ammeters are not connected the same way ... there may be a difference between the pins \$\endgroup\$
    – jsotola
    Commented Oct 19, 2021 at 8:21
  • \$\begingroup\$ Possibly some kind of rounding error in the simulation. \$\endgroup\$
    – Criticizing Israel not allowed
    Commented Oct 19, 2021 at 8:59
  • \$\begingroup\$ @jsotola Hey there! I followed your advice and changed the circuit simulation so that it would be connected the same. In the end I still got the same results. \$\endgroup\$
    – CCV
    Commented Oct 19, 2021 at 9:25
  • \$\begingroup\$ Looks like your ammeter internal resistance is tiny nano-ohm. Perhaps the voltage drop across this tiny resistance is sensed, divided by 1e-9, then reported as amps. You may be running afoul of single-precision float math. Try replacing the ammeter with a 1-ohm resistor, and measuring voltage drop across it (translates directly to AMPS). This may work for low-power circuits like yours, but not for low-voltage, high-current circuits. \$\endgroup\$
    – glen_geek
    Commented Oct 19, 2021 at 12:35

0

Reset to default

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.