PSpice Ratiometric Simulations

Started by Bob Penoyer November 14, 2012
This is not a school question. It's a real-life question.

Suppose three resistors are connected to a common node. The other end
of each resistor is connected to a voltage source.

So V1 is connected to R1, V2 is connected to R2, and V3 is connected
to R3. The opposite terminal of each resistor connects R1, R2, and R3
together.

I want to use PSpice Monte Carlo to observe the voltage at the common
node.

R1 is a 1% resistor.

R2 and R3 are two resistors in a single package. Their tolerance is 1%
but the tolerance of their ratio is 0.1%.

How can PSpice Monte Carlo be used to accurately determine the
possible voltages of the common node?
On Wednesday, November 14, 2012 6:48:34 AM UTC+2, Bob Penoyer wrote:
> This is not a school question. It's a real-life question. > > > > Suppose three resistors are connected to a common node. The other end > > of each resistor is connected to a voltage source. > > > > So V1 is connected to R1, V2 is connected to R2, and V3 is connected > > to R3. The opposite terminal of each resistor connects R1, R2, and R3 > > together. > > > > I want to use PSpice Monte Carlo to observe the voltage at the common > > node. > > > > R1 is a 1% resistor. > > > > R2 and R3 are two resistors in a single package. Their tolerance is 1% > > but the tolerance of their ratio is 0.1%. > > > > How can PSpice Monte Carlo be used to accurately determine the > > possible voltages of the common node?
This might get you started. Got the basic idea from elsewhere on the web , so no credit to me :0) It does a worst case analysis 1% on all resistors , but I have NOT done the 0.1% ratio calculation. I'm sure someone can improve , but it will get you started. Use LTSpice. Version 4 SHEET 1 880 680 WIRE 176 -32 16 -32 WIRE 320 -32 176 -32 WIRE 432 -32 320 -32 WIRE 16 16 16 -32 WIRE 176 16 176 -32 WIRE 320 16 320 -32 WIRE 16 160 16 96 WIRE 176 160 176 96 WIRE 320 160 320 96 WIRE 176 240 16 240 WIRE 320 240 176 240 WIRE 176 256 176 240 FLAG 176 256 0 FLAG 432 -32 Vout SYMBOL voltage 16 144 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value 1 SYMATTR Value2 "" SYMATTR SpiceLine "" SYMBOL voltage 176 144 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V2 SYMATTR Value 2 SYMATTR Value2 "" SYMATTR SpiceLine "" SYMBOL voltage 320 144 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V3 SYMATTR Value 3 SYMATTR Value2 "" SYMATTR SpiceLine "" SYMBOL res 0 0 R0 WINDOW 3 -70 117 Left 2 SYMATTR InstName R1 SYMATTR Value {wc_a({R1},tola)} SYMBOL res 160 0 R0 WINDOW 3 -32 119 Left 2 SYMATTR InstName R2 SYMATTR Value {wc_a({R2},tola)} SYMBOL res 304 0 R0 WINDOW 3 68 68 Left 2 SYMATTR InstName R3 SYMATTR Value {wc_a({R3},tola)} TEXT -264 -24 Left 2 !.param tola=0.01 TEXT -264 296 Left 2 !.function wc_a(nom,tola) if(run==1,nom,if(flat(1)>0,nom*(1+tola),nom*(1-tola))) TEXT -264 -64 Left 2 !.step param run 1 40 1 TEXT -264 328 Left 2 !.tran 1 TEXT -264 24 Left 2 !.param R1 = 1k TEXT -264 64 Left 2 !.param R2 = 2k TEXT -264 104 Left 2 !.param R3 = 2k
On Tue, 13 Nov 2012 20:48:17 -0800, Bob Penoyer
<bob@NOSPAMbobpenoyer.com> wrote:

>This is not a school question. It's a real-life question. > >Suppose three resistors are connected to a common node. The other end >of each resistor is connected to a voltage source. > >So V1 is connected to R1, V2 is connected to R2, and V3 is connected >to R3. The opposite terminal of each resistor connects R1, R2, and R3 >together. > >I want to use PSpice Monte Carlo to observe the voltage at the common >node. > >R1 is a 1% resistor. > >R2 and R3 are two resistors in a single package. Their tolerance is 1% >but the tolerance of their ratio is 0.1%. > >How can PSpice Monte Carlo be used to accurately determine the >possible voltages of the common node?
Parameterize the _value_ of R2 and R3. Then Monte Carlo on the parameter and the ratio? ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On Tue, 13 Nov 2012 20:48:17 -0800, Bob Penoyer
<bob@NOSPAMbobpenoyer.com> wrote:

>This is not a school question. It's a real-life question. > >Suppose three resistors are connected to a common node. The other end >of each resistor is connected to a voltage source. > >So V1 is connected to R1, V2 is connected to R2, and V3 is connected >to R3. The opposite terminal of each resistor connects R1, R2, and R3 >together. > >I want to use PSpice Monte Carlo to observe the voltage at the common >node. > >R1 is a 1% resistor. > >R2 and R3 are two resistors in a single package. Their tolerance is 1% >but the tolerance of their ratio is 0.1%. > >How can PSpice Monte Carlo be used to accurately determine the >possible voltages of the common node?
You could make R2 and R3 each from two resistors in series, and apply different Monte Carlo rules to them, specifically lock R2A and R3A to the same value and flog them 1%, but let the other two be independent and vary 0.1%. Something could be done with a Y-configuration representing R2 and R3, but takes more thinking. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Jim Thompson a &#2013265929;crit :
> On Tue, 13 Nov 2012 20:48:17 -0800, Bob Penoyer > <bob@NOSPAMbobpenoyer.com> wrote: > >> This is not a school question. It's a real-life question. >> >> Suppose three resistors are connected to a common node. The other end >> of each resistor is connected to a voltage source. >> >> So V1 is connected to R1, V2 is connected to R2, and V3 is connected >> to R3. The opposite terminal of each resistor connects R1, R2, and R3 >> together. >> >> I want to use PSpice Monte Carlo to observe the voltage at the common >> node. >> >> R1 is a 1% resistor. >> >> R2 and R3 are two resistors in a single package. Their tolerance is 1% >> but the tolerance of their ratio is 0.1%. >> >> How can PSpice Monte Carlo be used to accurately determine the >> possible voltages of the common node? > > Parameterize the _value_ of R2 and R3. Then Monte Carlo on the > parameter and the ratio? >
The real question being: does one need spice for such a simple answer that should take no more than 2 or 3 lines? -- Thanks, Fred.
On Wed, 14 Nov 2012 21:06:17 +0100, Fred Bartoli <" "> wrote:

>Jim Thompson a &#2013265929;crit : >> On Tue, 13 Nov 2012 20:48:17 -0800, Bob Penoyer >> <bob@NOSPAMbobpenoyer.com> wrote: >> >>> This is not a school question. It's a real-life question. >>> >>> Suppose three resistors are connected to a common node. The other end >>> of each resistor is connected to a voltage source. >>> >>> So V1 is connected to R1, V2 is connected to R2, and V3 is connected >>> to R3. The opposite terminal of each resistor connects R1, R2, and R3 >>> together. >>> >>> I want to use PSpice Monte Carlo to observe the voltage at the common >>> node. >>> >>> R1 is a 1% resistor. >>> >>> R2 and R3 are two resistors in a single package. Their tolerance is 1% >>> but the tolerance of their ratio is 0.1%. >>> >>> How can PSpice Monte Carlo be used to accurately determine the >>> possible voltages of the common node? >> >> Parameterize the _value_ of R2 and R3. Then Monte Carlo on the >> parameter and the ratio? >> > >The real question being: does one need spice for such a simple answer >that should take no more than 2 or 3 lines?
You didn't include the "2 or 3 lines" ?:-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Jim Thompson a &#2013265929;crit :
> On Wed, 14 Nov 2012 21:06:17 +0100, Fred Bartoli <" "> wrote: > >> Jim Thompson a &#2013265929;crit : >>> On Tue, 13 Nov 2012 20:48:17 -0800, Bob Penoyer >>> <bob@NOSPAMbobpenoyer.com> wrote: >>> >>>> This is not a school question. It's a real-life question. >>>> >>>> Suppose three resistors are connected to a common node. The other end >>>> of each resistor is connected to a voltage source. >>>> >>>> So V1 is connected to R1, V2 is connected to R2, and V3 is connected >>>> to R3. The opposite terminal of each resistor connects R1, R2, and R3 >>>> together. >>>> >>>> I want to use PSpice Monte Carlo to observe the voltage at the common >>>> node. >>>> >>>> R1 is a 1% resistor. >>>> >>>> R2 and R3 are two resistors in a single package. Their tolerance is 1% >>>> but the tolerance of their ratio is 0.1%. >>>> >>>> How can PSpice Monte Carlo be used to accurately determine the >>>> possible voltages of the common node? >>> Parameterize the _value_ of R2 and R3. Then Monte Carlo on the >>> parameter and the ratio? >>> >> The real question being: does one need spice for such a simple answer >> that should take no more than 2 or 3 lines? > > You didn't include the "2 or 3 lines" ?:-) >
Come on... I carefully wrote 1 2/3 lines to hint you in the right direction, leaving you 1 1/3 line to complete the answer :-) Now you have between 20 and 30 characters left. That's getting to be tough. -- Thanks, Fred.
On Wed, 14 Nov 2012 21:48:54 +0100, Fred Bartoli <" "> wrote:

>Jim Thompson a &#2013265929;crit : >> On Wed, 14 Nov 2012 21:06:17 +0100, Fred Bartoli <" "> wrote: >> >>> Jim Thompson a &#2013265929;crit : >>>> On Tue, 13 Nov 2012 20:48:17 -0800, Bob Penoyer >>>> <bob@NOSPAMbobpenoyer.com> wrote: >>>> >>>>> This is not a school question. It's a real-life question. >>>>> >>>>> Suppose three resistors are connected to a common node. The other end >>>>> of each resistor is connected to a voltage source. >>>>> >>>>> So V1 is connected to R1, V2 is connected to R2, and V3 is connected >>>>> to R3. The opposite terminal of each resistor connects R1, R2, and R3 >>>>> together. >>>>> >>>>> I want to use PSpice Monte Carlo to observe the voltage at the common >>>>> node. >>>>> >>>>> R1 is a 1% resistor. >>>>> >>>>> R2 and R3 are two resistors in a single package. Their tolerance is 1% >>>>> but the tolerance of their ratio is 0.1%. >>>>> >>>>> How can PSpice Monte Carlo be used to accurately determine the >>>>> possible voltages of the common node? >>>> Parameterize the _value_ of R2 and R3. Then Monte Carlo on the >>>> parameter and the ratio? >>>> >>> The real question being: does one need spice for such a simple answer >>> that should take no more than 2 or 3 lines? >> >> You didn't include the "2 or 3 lines" ?:-) >> > >Come on... >I carefully wrote 1 2/3 lines to hint you in the right direction, >leaving you 1 1/3 line to complete the answer :-) >Now you have between 20 and 30 characters left. That's getting to be tough.
I was yanking your chain. It's a simple Algebraic expression. I don't (generally) do Monte Carlo... I do worst case. If I pass worst case I know I'll pass _any_ Monte Carlo. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On 14.11.12 6:48 , Bob Penoyer wrote:
> This is not a school question. It's a real-life question. > > Suppose three resistors are connected to a common node. The other end > of each resistor is connected to a voltage source. > > So V1 is connected to R1, V2 is connected to R2, and V3 is connected > to R3. The opposite terminal of each resistor connects R1, R2, and R3 > together. > > I want to use PSpice Monte Carlo to observe the voltage at the common > node. > > R1 is a 1% resistor. > > R2 and R3 are two resistors in a single package. Their tolerance is 1% > but the tolerance of their ratio is 0.1%. > > How can PSpice Monte Carlo be used to accurately determine the > possible voltages of the common node? >
You can use the known ratio tolerance, if you change the circuit part with R2, R3, V2, and V3 to a de Thevenin equivalent circuit, applying the resistance tolerance to the internal resistance and the ratio tolerance to the equivalent EMF of the de Thevenin voltage source. -- Tauno Voipio
On Wed, 14 Nov 2012 13:52:29 -0700, Jim Thompson wrote:

> On Wed, 14 Nov 2012 21:48:54 +0100, Fred Bartoli <" "> wrote: > >>Jim Thompson a &eacute;crit : >>> On Wed, 14 Nov 2012 21:06:17 +0100, Fred Bartoli <" "> wrote: >>> >>>> Jim Thompson a &eacute;crit : >>>>> On Tue, 13 Nov 2012 20:48:17 -0800, Bob Penoyer >>>>> <bob@NOSPAMbobpenoyer.com> wrote: >>>>> >>>>>> This is not a school question. It's a real-life question. >>>>>> >>>>>> Suppose three resistors are connected to a common node. The other >>>>>> end of each resistor is connected to a voltage source. >>>>>> >>>>>> So V1 is connected to R1, V2 is connected to R2, and V3 is >>>>>> connected to R3. The opposite terminal of each resistor connects >>>>>> R1, R2, and R3 together. >>>>>> >>>>>> I want to use PSpice Monte Carlo to observe the voltage at the >>>>>> common node. >>>>>> >>>>>> R1 is a 1% resistor. >>>>>> >>>>>> R2 and R3 are two resistors in a single package. Their tolerance is >>>>>> 1% but the tolerance of their ratio is 0.1%. >>>>>> >>>>>> How can PSpice Monte Carlo be used to accurately determine the >>>>>> possible voltages of the common node? >>>>> Parameterize the _value_ of R2 and R3. Then Monte Carlo on the >>>>> parameter and the ratio? >>>>> >>>> The real question being: does one need spice for such a simple answer >>>> that should take no more than 2 or 3 lines? >>> >>> You didn't include the "2 or 3 lines" ?:-) >>> >>> >>Come on... >>I carefully wrote 1 2/3 lines to hint you in the right direction, >>leaving you 1 1/3 line to complete the answer :-) Now you have between >>20 and 30 characters left. That's getting to be tough. > > I was yanking your chain. It's a simple Algebraic expression. I don't > (generally) do Monte Carlo... I do worst case. If I pass worst case I > know I'll pass _any_ Monte Carlo. > > ...Jim Thompson
Worst case in this instance means only testing eight points, so one does wonder why they can't start there... -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com