How come a zero value resistor is not supported? It took me awhile to figure out this was a problem and resulting in cryptic nan(ind) reported node values. The documentation does’t indicate 0 is not supported. I don’t recall this being an issue in other spice, or is it? Does one need to use {GMIN} or something?
Hello @Hans_Goldenrod you can use a very low value like 1n ohms or you can right click and “stuff with jumper” which is handy.
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And yes V/R=I is not defined when R->0, probably other spice checks for div by zero and inserts some very small R for you.
In LTspice, 0 ohms resistor is ignored in netlist generation, simulator don’t have to handle a 0 ohms resistor if your netlist is created through schematic. But if you force LTspice to run a netlist with 0 ohms resistor, it will have an error. So, which spice can accept a zero ohms?
For Qspice, may be you can report this to Mike a 0ohms added in circuit will mess thing up.
As a side note to this discussion: QSpice supports a feature where a 2-terminal device can be defined as a jumper.
Since most designers use 0 ohm resistors as jumpers under certain configurations, you can define the resistor as some value under one configuration and then use the “jumper” under another configuration.
Len
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I believe the reason for not allowing a a component value to be “0” is that when some math is performed on the circuit nodes, it is possible that a DIV BY ZERO might occur.
In reality a 0 ohm resistor is not really practical (the exception might be with super-conducting materials near 0K). A practical 0 ohm resistor is many times closer to 1 mOhm.
Instead of using the jumper method, if you use the same circuit under different configurations, you can use the step parameter method (ex: .step param R1 list 1n 100 1000). This allows you to create many sims of the same circuit with different values for one or more of your circuit components.
I use this all the time to get visual and quantitative results for RC, RLC and RL filters.
Len