# Question about using Ohms law to calculations with LTspice

#### anishkgt

Joined Mar 21, 2017
547
Hey all,

I am trying to find the resistance of a unknown resistor with know current and voltage using ohms law. based on the result attached is there a match function to simply do this
Ohms = 0.0034/1700
which is voltage from V(adc)/set current 1700.

#### Audioguru again

Joined Oct 21, 2019
3,170
I do not believe your voltage is only 3.4mV and the current is a massive 1700A!

#### anishkgt

Joined Mar 21, 2017
547
Its a spot welder project used to spot weld 18650 cells with nickel strips. That is the voltage drop at the nickel strip, with which the resistance is calculated using Ohm's law
R=V/I
=0.0034/1700 = 0.000002Ohms or 0.002mOhms

#### crutschow

Joined Mar 14, 2008
27,169
Plot V(ADC) by clicking on that node after a simulation run.
Right click on the V(ADC) title in the plot.
Change the expression to V(adc)/I(Rx) where Rx is the resistor carrying the current.

#### anishkgt

Joined Mar 21, 2017
547
Thank you, that plots a graph. Would it be possible to have it as label or something similar ?

#### Alec_t

Joined Sep 17, 2013
12,060
Do a DC operating point analysis instead of a Trans analysis.

#### atferrari

Joined Jan 6, 2004
4,320
It seems the OP does not use to distinguish between mA and A.
In other thread it looks like that.

#### anishkgt

Joined Mar 21, 2017
547
Since i did not get to make electronics as my day job its is a hobby, hence i find it hard to. But recently i am getting used to it.