# How do I draw the equivalent circuit for this diagram?

#### QA1311

Joined Dec 26, 2019
7
Hello! I have to represent these connections in an equivalent circuit

so I did this
Where Ry and Rx are the summations of parallel resistances..But I think it is incomplete and maybe incorrect. Could you please help ?

#### ericgibbs

Joined Jan 29, 2010
19,078
hi QA,
What about the switched resistors R12,13...15 in the OPA feedback loop.?
and say the DVM.
E

#### QA1311

Joined Dec 26, 2019
7
hi QA,
What about the switched resistors R12,13...15 in the OPA feedback loop.?
and say the DVM.
E
I added their reciprocals and represented them with Ry
Is this correct?

#### ericgibbs

Joined Jan 29, 2010
19,078
hi QA,
You cannot lump the resistors, they are individually selected by that rotary switch to set the Gain.
Show the switch.
E

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#### QA1311

Joined Dec 26, 2019
7
hi QA,
You cannot lump the resistors, they are individually selected by that rotary switch to set the Gain.
Show the switch.
E
First of all, thank you Eric for your help..
I don’t know how to represent a rotary switch but I did this

#### ericgibbs

Joined Jan 29, 2010
19,078
hi QA,
The dashed black line [ now high lighted in Green] indicates that the two switch elements are on the same switch knob.
Look at this image, the 'wiper' of the switch marked with a arrow head, points to the switch contact which has been selected.
A rotary switch is normally drawn as a semi circle of dots, and the wiper as an arrow, use a dashed line to show that the two sections are on the same switch.
OK.?
E
BTW: Your drawing is incorrect, it shows individual switches.

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#### QA1311

Joined Dec 26, 2019
7
hi QA,
The dashed black line [ now high lighted in Green] indicates that the two switch elements are on the same switch knob.
Look at this image, the 'wiper' of the switch marked with a arrow head, points to the switch contact which has been selected.
A rotary switch is normally drawn as a semi circle of dots, and the wiper as an arrow, use a dashed line to show that the two sections are on the same switch.
OK.?
E
BTW: Your drawing is incorrect, it shows individual switches.
I got it now. Thank you very much for your help

#### Kjeldgaard

Joined Apr 7, 2016
476
The resistors R16, R17, R18, R19 is not connected right.