What is this thing for ?

[raimis100]

Hello.

I would appreciate a help from you guys.

**broken link removed**

Can you please say me what is the red circled thing and what does it do on the circuit ?

 

[dknguyen]

It's a variable resistor connected between the null adjustment pins of the op-amp. This allows for an adjustment to null the op-amp offset due to bias currents (among other causes).

 

[Nigel Goodwin]

It's the correct symbol for a preset potentiometer, and is for setting the offset null on the opamp.

For some reason the USA still use the antique symbols, pre-1960's?.

 

[crutschow]

For some reason the USA still use the antique symbols, pre-1960's?.

Probably the same reason many spell analog, analogue. It's Tradition! But I think a zig-zag line is easier to interpret as a resistor, as compared to a rectangular box, which could be anything, just as two parallel plates represent a capacitor, and a series of looped lines represents an inductor, better than a box or circle would.

 

[colin55]

The rectangular box was introduced because original drawing packages did not have the zig zag capability. In addition, the resistor value could be placed inside the rectangle. I changed from zig zag over 30 years ago for this very reason.

 

[bychon]

For some reason ramis100, a person with 2 posts and no indication of country of origin posted a drawing that nobody knows from whence it came.