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14th October 2019, 18:50 #1
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Zener diode simulation problem using multisim 12.0
Hello,
I am new to multisim and just started learning how to simulate basic circuits. I am using multisim 12.0.
I am trying to simulate a basic zener diode circuit and trying to observe the effect of changing the load resistance.
I believe this needs to be done using parameter sweep.
The problem I am facing is, in the parameter sweep window, I am not seeing my load resistor name in the drop down list of the component name I want to sweep. I am seeing r1:xrload, r1:xr1. r1:xr2, r2:xrload etc. At the same time, I am seeing that the present value of r1:xrload and r2:xrload is set to 5k. My load resistor value has been set to 10k in the schematic. Another peculiar thing is, I don't have any r2 resistor in my circuit. Could anyone kindly help me out regarding this? My questions are:
1) What are these r1:xrload, r1:xr1. r1:xr2, r2:xrload etc.
2) How is my rload value getting halved?
3) I have also looked at the netlist as well, and it shows 10000/2 there as well. Could anyone please tell me why?
I will really appreciate some help in understanding what's going on here. Thank you.
P.S. I have looked at the multisim forum and I couldn't find a relevant problem. The youtube tutorials also don't have such weird names in the name field.
I am attaching the screenshot herewith.
Additional circuit info:
Components used: DC_Power for voltage source, resistor_rated for r1 and rload, zener (virtual) for the zener diode.Attachment 156035Last edited by KlausST; 14th October 2019 at 20:32. Reason: Disabled smilies

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15th October 2019, 03:17 #2
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Re: Zener diode simulation problem using multisim 12.0
Your attachment cannot be seen because it is invalid.

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15th October 2019, 04:24 #3
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Re: Zener diode simulation problem using multisim 12.0
https://imgur.com/gallery/sRXpvzg
Sorry, please let me know if this works.

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15th October 2019, 07:57 #4
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Re: Zener diode simulation problem using multisim 12.0
Did you try a similar circuit from the examples folder?
Did the same problem appear with simpler circuits? Say, a resistor and voltage source?
Once you get a simple circuit to work, then add components.

15th October 2019, 08:28 #5
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Re: Zener diode simulation problem using multisim 12.0
Yes, tried and failed. Same thing appears. I have scoured the multisim forum. From what I could find is that this expression should appear for the pots (with the wiper dividing the 2 resistors in the pots) which is weird as I have used the RESISTOR_RATED component and not the pot.
I have tried just a simple voltage source and a resistor. I am attaching the screenshot herewith.
Notice that r2 is appearing even though I have called only 1 resistor.
I should mention this that DC and transient analysis works perfectly.
https://imgur.com/gallery/RkgXdD6

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16th October 2019, 16:29 #6
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Re: Zener diode simulation problem using multisim 12.0
I do not know what you are trying to do.
1) You have a 5V Zener diode with no part number and no spec's. Nobody makes one but 5.1V is common so my calculations use 5.1V.
2) You are simulating sweeping the load resistance. Why?
I do not know if Multisim has a library full of Zener diode datasheets. A 1N5231B Zener diode is 5.1V only when its current is 20mA. At less current then its voltage is less. Around 0.25mA its voltage regulation is very poor.
You have a 16V supply and a 10k load. The load current is 5.1V/10k= 0.51mA. The current in the 470 ohm resistor is (16V5.1V)/470 ohms= 23.2mA. Then the current in the Zener diode is 23.2mA  0.51mA= 22.7mA so the voltage will be very close to the rated +5% which is for a current of 20mA.
For such a low load current of only 0.5mA then I would use a Zener diode that is rated at a current less than 20mA like 5mA. A 1N5993B is 5.1V rated at 5mA then the resistor feeding it can be (16V  5.1V)/5.5mA= 1982 ohms, use 2k ohms.
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