resistor with random variable number not working

Hello i have many simulink blocksets,

i have tried to put rf blockset in order to build a ressistor with random value in it as shonn bellow.

but its not working .Where did i go wrong?

Answer 1

[Ameer Hamza]

There is no need to add randn(1) in the resistor value. As the documentation page mentions: https://www.mathworks.com/help/simrf/ref/variableresistor.html you just need to tick the "Simulate noise" checkbox. In the resistance field, just type 50. Also, make sure that the "simulate noise" box is ticked in RF-blockset configuration block.

[fima v]

Hello Ameer , in the following manual i have found Tollerance option.

is there a way to have such "tollerance" option to a voltage source?(so i will have a small random option to a DC source) i need 255 such sources for 8bit flash adc.

https://www.mathworks.com/help/physmod/sps/ref/resistor.html#bvo5ux6-3

[Ameer Hamza]

Which voltage source are you referring to? For example, this voltage source has the option to enable noise: https://www.mathworks.com/help/releases/R2020a/physmod/sps/ref/voltagesource.html

[fima v]

Hello Ameer, i am looking for avoltage source with a little offset (set randomly aroundsome DC value) exactly like the tollerance option in the resistor..

It would be great if you could recomment me such a component.

Thanks.

[Ameer Hamza]

The voltage source suggested in my last comment does that. You can specify the power of the noise signal and it will add that noise to nominal DC value.

[fima v]

Hello Amer that the problem i hace a DC source for example 1V

i want it to vary by 0.1V so you say i should add 0.01 V^2/Hz in the noise to represent it?

Thanks

[Ameer Hamza]

It seems correct, but I am not entirely sure. You may need to do some experiments by connecting this block with the scope and observing the variation in voltage value.

[fima v]

another thing is that this voltage source is connected into an opamp where i have defined in the opamp some input noise.

Will the noise from the voltage source and input noise of the opamp will be in a conflict by MATLAB behavior? how they will play together?

Thanks.

[Ameer Hamza]

It is difficult to predict. You will need to run the model to check if it works.