# LTSpice-Simulation

Discussion in 'General Electronics Chat' started by ayractgc, Feb 24, 2018.

1. ### ayractgc Thread Starter Member

Feb 3, 2018
52
0
I want to show Vout-R5 graphics.R5 is a variable resistor that changes its resistance between 300 ohm and 700 ohm.I want to add R5 to x-axis and Vout y axis.Can you help me ?I don't know the LTspice so good.I added the screen shot and test file

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2. ### ericgibbs Moderator

Jan 29, 2010
6,552
1,270
hi ay,
This is one option.
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3. ### ayractgc Thread Starter Member

Feb 3, 2018
52
0
But ı didn't want time in x-axis.I want to add resistance change in x- axis how can ı do?

4. ### ericgibbs Moderator

Jan 29, 2010
6,552
1,270
Hi,
If you check the plot you do not have the Time in the Xaxis, it goes from 300 to 700, Ohms, which represents the resistance change you asked for.
E

5. ### ayractgc Thread Starter Member

Feb 3, 2018
52
0
How did you apply this?With add trace ?Because when i click add trace i see just voltages and current of the nodes but i didn't see resistance?

6. ### ayractgc Thread Starter Member

Feb 3, 2018
52
0
How can i identify a value in x-axis such that ;
R5-555ohm
that shows the delta R5
How can i do this equation?

7. ### eetech00 Senior Member

Jun 8, 2013
1,256
253
Hi

You didn't include the model or symbol file for the INA, so I'll try to describe how to graph resistance.

Label the wires on each side of R5 so you can specify a voltage drop. Then, use an expression in the waveform viewer. I you want the plot to show R5 as resistance, use an ohms law expression:

V(N1,N2) / I(R5)

where N1 and N2 are the labeled wires on each side of R5

R5 Value should show up as Ohms in the waveform viewer.

You can also use a .meas statement using the same approach.

.meas Rx param V(N1,N2) / I(R5)

Then view the results in the error log.

eT

Last edited: Feb 24, 2018
8. ### ericgibbs Moderator

Jan 29, 2010
6,552
1,270
hi ay,
This should make it more easily to follow,
A 400R Pot in series with a 300R resistor, the plot shows the X-axis as Resistance, Yaxis Vout.

If you place the cursor on a blank space of the X axis you should see the cursor change to a rule, left click and a pop up window will appear.
See image A004.
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• ###### INA18_simulationWB2.asc
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9. ### eetech00 Senior Member

Jun 8, 2013
1,256
253
Here's another way do this (review the attached image before proceeding):

1. This model has trouble finding a dc operating point, so append .uic to the tran statement.
2. Add some reasonable resistance to the voltage sources (no voltage source has 0 resistance).
100 milli_ohms is a good number.
3. Set the +/- inputs to the INA initially to zero.

Then,
1. Add two .meas statements to the schematic for v_out and R_ohms
2. Run the sim
3. When the sim is complete, view the error log.
4. Scroll thru the log and find R_ohms. Right-click on R_ohms and select "plot step'd meas data".
A new graph will open. R_ohms will be displayed in the X-axis
5. Right click on the new graph. Select "add trace", then select V_OUT. V_OUT will be displayed in the Y-axis

eT

Last edited: Feb 25, 2018
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10. ### ayractgc Thread Starter Member

Feb 3, 2018
52
0
I exported the results as a notefile.How can ı convert them to a excel file i don't know to read this file?

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11. ### eetech00 Senior Member

Jun 8, 2013
1,256
253
Hi

Excel can import a txt file.
You'll have to read the excel help to do that.

eT

12. ### ericgibbs Moderator

Jan 29, 2010
6,552
1,270
hi ay,
In Excel you have to use OPEN , a window should appear asking the Type, select TEXT, then expand the box width to show the data.

I have done it in Lotus and saved as a XLS file.
In order to upload here I have changed the extension to .txt , change it back to .xls

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