help with circuit sim

Discussion in 'General Electronics Chat' started by kingArgon, Mar 14, 2012.

  1. kingArgon

    Thread Starter Member

    Mar 20, 2011
    Maybe this is something for the LTSpice forum but it has been happening in every circuit sim i use. I am trying to simulate the circuit in one of the tutorials. Specifically
    the resistances are 3k,5k, 10k and the voltage is 9volts. in the sim the voltage drop across the 3k resistor is 7.5v and across the 5k its 2.4999 volts. which would mean i gained a volt. can someone help me?
  2. MrChips


    Oct 2, 2009
    You are obviously measuring your voltages incorrectly.

    The current is 0.5mA

    The voltage across 3k is 1.5V
    The voltage across 10k is 5.0V
    The voltage across 5k is 2.5V

    What you are measuring is the voltage at the junctions 2 and 3 with respect to junction 4.

    You are confusing the terms "voltage at" and "voltage across".
    Voltages are always measured with respect to something. It is always a voltage difference or a "voltage drop" or "voltage across".
  3. Ron H

    AAC Fanatic!

    Apr 14, 2005
    To measure the voltage from one node to another, put the probe on one of the nodes, then left click and hold while you drag the probe (it will turn black) to the other node, then release. The voltage on the first node will be relative to the voltage on the second node.
  4. kingArgon

    Thread Starter Member

    Mar 20, 2011
    thankyoou Mr.Chips and Ron for the quick response.

    Ron that was the issue, i was just measuring wrong. its working now! :))