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user16222

Let's take a simple voltage divider AND you are only interested in resistor tolerances, not supply tolerances (assume psu is ideal)

enter image description here

It is trivial to calculate the nominal, minimum and maximum

max: \$10\cdot \frac{10k*1.01}{(10k*1.01) + (10k*0.99)}\$ = 5.05V

nom: \$10\cdot \frac{10k}{10k + 10k}\$ = 5V

min:\$10\cdot \frac{10k*0.99}{(10k*1.01) + (10k*0.99)}\$ = 4.95V

Can a Monte-Carlo output this value? Probably, a very very VERY small probably occurrence. Why?

A Monte-Carlo simulation will generate a random value within stated bounds (normal distributed, 1%, mean value). Statistically speaking it could generate, but this is a one in a millionbillion type occurrence. To then pick the absolute max and hte absolute minimum, in the same run? I would rather bet on a national lottery.

enter image description here

The absolute max/min output "worst of the worst" is a best suited for pen & paper, excel, mathCAD, Jupyter etc ... and is extremely valuable in determining whether a design will operate over all possible tolerances (very useful for stress calculations). Real world type behaviour? the probabilistic approach relies on these types of sweeps.

In practice both are useful as you can take credit since 6\$\sigma\$ covers 99.999997% and thus anything outside of this is 3.4 errors per million

So in short.. Will a Monte-Carlo run provide the extreme outputs? probably. If you want to know the extreme outputs then most tool can be set for extreme value calculation, but you need to guide them to determine which combination will provide the maximum/minimum

Let's take a simple voltage divider AND you are only interested in resistor tolerances, not supply tolerances (assume psu is ideal)

enter image description here

It is trivial to calculate the nominal, minimum and maximum

max: \$10\cdot \frac{10k*1.01}{(10k*1.01) + (10k*0.99)}\$ = 5.05V

nom: \$10\cdot \frac{10k}{10k + 10k}\$ = 5V

min:\$10\cdot \frac{10k*0.99}{(10k*1.01) + (10k*0.99)}\$ = 4.95V

Can a Monte-Carlo output this value? Probably, a very very VERY small probably occurrence. Why?

A Monte-Carlo simulation will generate a random value within stated bounds (normal distributed, 1%, mean value). Statistically speaking it could generate, but this is a one in a million type occurrence. To then pick the absolute max and hte absolute minimum, in the same run? I would rather bet on a national lottery.

enter image description here

Let's take a simple voltage divider AND you are only interested in resistor tolerances, not supply tolerances (assume psu is ideal)

enter image description here

It is trivial to calculate the nominal, minimum and maximum

max: \$10\cdot \frac{10k*1.01}{(10k*1.01) + (10k*0.99)}\$ = 5.05V

nom: \$10\cdot \frac{10k}{10k + 10k}\$ = 5V

min:\$10\cdot \frac{10k*0.99}{(10k*1.01) + (10k*0.99)}\$ = 4.95V

Can a Monte-Carlo output this value? Probably, a very very VERY small probably occurrence. Why?

A Monte-Carlo simulation will generate a random value within stated bounds (normal distributed, 1%, mean value). Statistically speaking it could generate, but this is a one in a billion type occurrence. To then pick the absolute max and hte absolute minimum, in the same run? I would rather bet on a national lottery.

enter image description here

The absolute max/min output "worst of the worst" is a best suited for pen & paper, excel, mathCAD, Jupyter etc ... and is extremely valuable in determining whether a design will operate over all possible tolerances (very useful for stress calculations). Real world type behaviour? the probabilistic approach relies on these types of sweeps.

In practice both are useful as you can take credit since 6\$\sigma\$ covers 99.999997% and thus anything outside of this is 3.4 errors per million

So in short.. Will a Monte-Carlo run provide the extreme outputs? probably. If you want to know the extreme outputs then most tool can be set for extreme value calculation, but you need to guide them to determine which combination will provide the maximum/minimum

Source Link
user16222
user16222

Let's take a simple voltage divider AND you are only interested in resistor tolerances, not supply tolerances (assume psu is ideal)

enter image description here

It is trivial to calculate the nominal, minimum and maximum

max: \$10\cdot \frac{10k*1.01}{(10k*1.01) + (10k*0.99)}\$ = 5.05V

nom: \$10\cdot \frac{10k}{10k + 10k}\$ = 5V

min:\$10\cdot \frac{10k*0.99}{(10k*1.01) + (10k*0.99)}\$ = 4.95V

Can a Monte-Carlo output this value? Probably, a very very VERY small probably occurrence. Why?

A Monte-Carlo simulation will generate a random value within stated bounds (normal distributed, 1%, mean value). Statistically speaking it could generate, but this is a one in a million type occurrence. To then pick the absolute max and hte absolute minimum, in the same run? I would rather bet on a national lottery.

enter image description here