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Defining time parameter

Posted Sep 5, 2022, 8:07 a.m. EDT Version 6.0 6 Replies

Lampros Papadopoulos BFH Praktikant
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I would like to insert a sinus waveform as an input for electric potential. For that to happen, I need to instert the time parameter. I have tried many ways but I get errors like":

"Error in multiphysics compilation. Syntax error in expression. - Expression: [sec] - Subexpression: [sec] - Position: 1"

Could anyone help? Thanks in advance.

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6 Replies Last Post Sep 8, 2022, 8:35 a.m. EDT
Magnus Ringh COMSOL Employee

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Posted: 2 years ago Sep 5, 2022, 8:42 a.m. EDT

Hi Lampros,

To define seconds, use [s] or [second]; [sec] is not a valid unit in COMSOL Multiphysics. SI prefixes are also supported, such as [ms] for milliseconds, as well as [min], [h], and [a] for minutes, hours, and years, respectively. See the user documentation for a full list of supported unit systems, units, and SI prefixes.

Best regards,

Magnus

Hi Lampros, To define seconds, use `[s]` or `[second]`; `[sec]` is not a valid unit in COMSOL Multiphysics. SI prefixes are also supported, such as `[ms]` for milliseconds, as well as `[min]`, `[h]`, and `[a]` for minutes, hours, and years, respectively. See the user documentation for a full list of supported unit systems, units, and SI prefixes. Best regards, Magnus
Lampros Papadopoulos BFH Praktikant
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Posted: 2 years ago Sep 5, 2022, 9:05 a.m. EDT

Hello Magnus,

First of all, thank you for the quick responce. Yes, I have tried that too. That does not seem to be the problem. Even if I change [sec] to [s]. I get the exact same error:

"Error in multiphysics compilation. Syntax error in expression. - Expression: [s] - Subexpression: [s] - Position: 1"

Best regards, Lampros

Hello Magnus, First of all, thank you for the quick responce. Yes, I have tried that too. That does not seem to be the problem. Even if I change [sec] to [s]. I get the exact same error: "Error in multiphysics compilation. Syntax error in expression. - Expression: [s] - Subexpression: [s] - Position: 1" Best regards, Lampros
Magnus Ringh COMSOL Employee

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Posted: 2 years ago Sep 5, 2022, 9:29 a.m. EDT

Hi Lampros,

Then there is some other issue with the expression. I think you need to display the entire expression for us to be able to pinpoint what could be wrong.

Best regards,

Magnus

Hi Lampros, Then there is some other issue with the expression. I think you need to display the entire expression for us to be able to pinpoint what could be wrong. Best regards, Magnus
Dave Greve Certified Consultant
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Posted: 2 years ago Sep 5, 2022, 1:41 p.m. EDT

The argument for the function Vin must be dimensionless. Try using Vin(t/1[s]).

The argument for the function Vin must be dimensionless. Try using Vin(t/1[s]).
Jeff Hiller COMSOL Employee

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Posted: 2 years ago Sep 6, 2022, 4:05 p.m. EDT

Hello Lampros,

The problem is your Variable 3 node, which you use to define a variable t as [sec]. In a time-dependent analysis, t is automatically defined as time, so you do not need to create this Variable 3 node at all, and you can -and should- remove it; as Magnus mentioned already [sec] is not a valid expression, it's not even the right notation for "second", [s] is ; this is causing the error. When you remove that node, the compilation error disappears.

With that said, I have not let your model run to completion, so there may be other issues with your set-up.

Best,

Jeff

-------------------
Jeff Hiller
Hello Lampros, The problem is your Variable 3 node, which you use to define a variable t as [sec]. In a time-dependent analysis, t is automatically defined as time, so you do not need to create this Variable 3 node at all, and you can -and should- remove it; as Magnus mentioned already [sec] is not a valid expression, it's not even the right notation for "second", [s] is ; this is causing the error. When you remove that node, the compilation error disappears. With that said, I have not let your model run to completion, so there may be other issues with your set-up. Best, Jeff
Lampros Papadopoulos BFH Praktikant
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Posted: 2 years ago Sep 8, 2022, 8:35 a.m. EDT

Ok, thank you all very much for your replies! Will look into it.

Ok, thank you all very much for your replies! Will look into it.

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