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IV Characteristics of diode using Keithley 2450

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I am a complete beginner and have been trying to understand how this works, I've looked around and decided to use it on Keithley 2450SMU. Starting with the IV characteristics of a diode seemed to be the easiest way to do this, but I can't find a proper Block diagram that can help me understand how to go through this.

Please provide me with the Block diagram for a diode iv characteristics with labels of initialize, configure and close functions for me to understand basic skeleton of how this goes usually.

I have downloaded the instrument drivers for Keithley 2450 and the software has detected its presence.

I have also tried the general examples that came in the examples with the drivers and they seemed to work too, but understanding block diagram was pretty difficult.

I've browsed the community and internet to find this block diagram but was unsuccessful.

Please provide help! 


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Message 1 of 20
Accepted by topic author beginner1234

Sounds like you have made a good start on your way to learning LabVIEW and the 2450.  If you have the driver code and the examples, that's all you need to learn how the program works.


Turn on the Help, by clicking CTRL+H, then mouse-over the subvis in order, read their descriptions.  Look at their inputs and outputs, or go one step further and open the subvis and study them as well.


Here's a posted sample I made years ago using the driver VIs - Re: Keithley 2450 Continuous current measurement - NI Community. (This does a single bias, read N times with a N second delay, not a diode IV but it serves the same purpose for learning.  Note its a snippet, which you can drag into a blank VI and the code with be generated for you.)


The first subvi initializes communication and resets the instrument state, the next 5 subvis setup the measurement, and the 7th subvi enable the bias.  Inside the While loop the Read VI triggers a measurement and returns the date to be plotted.  The first VI after the While loop turns the bias OFF while the next one close communications.


If there are parts of that you don't understand or want some explanation about, post here and we can try to explain more.


Hope that helps,


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Message 2 of 20
Accepted by topic author beginner1234

Something that might help you search for examples and such would be to search for "Keithley 2400" in addition to the 2450.  The 2450 came out around 5-10 years ago, while the 2400 (which does almost all the same functions, just an older model) came out something more like 20 or 25 years ago.

Message 3 of 20
Accepted by topic author beginner1234

Speaking of examples, I assume the OP is talking about the shipping example called "Keithley 2450 Sweep and Acquire".


There is nothing we could provide you that would be simpler than this example.  It is the bare minimum to get diode IV data and does pretty much exactly what you are trying to achieve. If you don't understand it, you should spend more time learning how to use the 2450 manually before trying to program it.  Then the example code will be clear.


The example:

1.  Inits the device.

2.  Configures the range for V and I.

3.  Configures the measurement functions.

4.  Sets up the ramp (sweep).

5.  Turns on the output.

6.  Initiates the sweep.

7.  Waits until the sweep is done.

8.  Reads the results data from the buffer.

9.  Turns off the output.

10.  Closes comms with the 2450.


This is the same thing you would do manually to get IV data.  It's just automated.  Try going through these steps using the 2450s front panel buttons so you understand the process of setting up the instrument and acquiring data.


Here's a simple 2450 diode IV tutorial I found.  There are lots of them including video guides:

IVChrzDIodes2450_AN1.PDF (


SMUs are relatively complex devices compared to DMMs and scopes.  Spend some time at your bench with a handful of diodes and LEDs and have some fun experimenting.  Don't use expensive diodes though and keep safety in mind!  (The 2450 can output 200V @ 1A.)


Let us know how it goes and feel free to ask questions.  


LabVIEW Pro Dev & Measurement Studio Pro (VS Pro) 2019 - Unfortunately now moving back to C#, .NET, Python due to forced change to subscription model by NI. 8^{
Message 4 of 20

Thank you for your swift reply and all the other solutions under the post helped as I now understand the skeleton of about how to make a simple block diagram for IV characteristics.

But I am stuck at the 'for loop' part, I am trying to put in the same elements in this for loop as the example from instrument drivers of keithley 2450 for sweep and acquiring measurements. Please tell me if that's the correct way or not and if it is not what can I possibly do to understand the 'for loop' part for IV characteristics.

Also where should I place the XY graph for IV characteristics: in the loop or outside it?

And almost as silly as it sounds, I have a question, can I use the same block diagram for IV characteristics of a diode and any other electronic if the input conditions are the same?

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Message 5 of 20

May I ask why there is no error in in this specific block diagram example? In the other examples, an error cluster was used.

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Message 6 of 20

Are there any videos that might help me understand these because I couldn't find ones that could help me yet.

Please link a few that might help me as a beginner, thank you.

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Message 7 of 20

This video series is quite good:


I only have LabVIEW 2021 installed and can't view your VI.  If you Save As Previous Version then I can have a look.

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Message 8 of 20

I am uploading the screenshots of both.

Download All
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Message 9 of 20

The waveform in this example is between current/voltage and time, let's say I need to plot an X-Y graph between Voltage and Current, then which parts of the block diagram must I eliminate, and which voltage and current output do I connect to X and Y axis of the graph?

I tried understanding by looking at context help but I didn't quite get it since they mostly are configuring of source and measurement.

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Message 10 of 20