# Calculate quarter bridge with INA125P

#### kauanmb

Joined Dec 19, 2023
6
Hey! I need any information on how i calculate a quarter bridge or if i can do this using the INA125P. The idea would be to make a "universal" connector to wich i can quickly connect a strain gauge or thermocouple and have the signal converted.

#### ericgibbs

Joined Jan 29, 2010
18,835
Hi kau,
Welcome to AAC.
Do you mean a quarter bridge, how would you plan to connect a single sensor element?
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#### kauanmb

Joined Dec 19, 2023
6
To be clearer, it would be something like the scm-sg120 adapter does.

#### ericgibbs

Joined Jan 29, 2010
18,835
Hi kau,
As you may already know, this type of adaptor consists of 3 precision resistors and the client's sensor makes the last arm of the full bridge.
So you are asking for a single design that covers all the common gauges of 120, 350, 700, or 1000-ohm?
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#### kauanmb

Joined Dec 19, 2023
6
That's right, but I have no idea how to do it or if it's possible. I bring the INA, as it is an IC that I have been using and I have some available.

#### ericgibbs

Joined Jan 29, 2010
18,835
Hi kau,
What you are asking is not an easy task, do you have any draft designs or sketches you could post.?

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#### kauanmb

Joined Dec 19, 2023
6
I stopped to think about it and, for now, it would be better to test initially with 120 ohms to prove the efficiency of the project. I imagine it would be easier to develop this way.

#### ericgibbs

Joined Jan 29, 2010
18,835
Hi k,
The bridges I use are usually 350R or 1000R , the 1000R is the PT sensor type.
You must use precision resistors say 0.01% on the other 3 arms of the bridge,

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#### kauanmb

Joined Dec 19, 2023
6
Can you send me a diagram, schematic or something that shows how the circuit is assembled?

#### ericgibbs

Joined Jan 29, 2010
18,835
Hi k,
Can you follow this copy of a LTSpice circuit, the IN125 is the dotted line rectangle/
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