# Need to design a Digital potentiometer circuit that has a wiper resistance of 0-10 ohm

#### saifudeen rizal

Joined Jun 5, 2018
50
Hai.,

guys help me to design a potentiometer circuit need to be of 1K with either 8 or 10 bits.

I have searched all the IC and every IC comes with a wiper resistance of minimum 50/100 ohms per wiper change..!
But i need the resistance to be of with 0-10 ohms per wiper change?
suggest me any circuit or ic to implement this ..!

Thanking you.,

#### dl324

Joined Mar 30, 2015
15,536
Is this school work?

Joined Feb 20, 2016
4,290
What about a "real" POT driven by a servo?

What sort of signal level are you need in the POT to control? Usually such a low value POT will be controlling some power device, not just low signals. More info for you application is needed.

#### crutschow

Joined Mar 14, 2008
32,097
Buffer the output of the wiper with a op amp follower so the wiper resistance will have no effect.

#### Alec_t

Joined Sep 17, 2013
13,456
Does the variable resistance need to be a true potentiometer (3-terminal device) or just a rheostat (2-terminal device)?
Is any terminal of the device grounded, or tied to some other power rail?
How much current will flow through it?

#### saifudeen rizal

Joined Jun 5, 2018
50
What about a "real" POT driven by a servo?

What sort of signal level are you need in the POT to control? Usually such a low value POT will be controlling some power device, not just low signals. More info for you application is needed.
Hai.,

The application that i am using is ..,
I am using the RTD where the output(Resistance) of RTD changes around 2-10 ohms of change per deg.,
so Thats why i need to design a ciruit...!

-saif

Does the variable resistance need to be a true potentiometer (3-terminal device) or just a rheostat (2-terminal device)?
Is any terminal of the device grounded, or tied to some other power rail?
How much current will flow through it?

Yes.,
it has to be a 3terminal device since my circuit deal with 3 wire RTD.,
The Board i am gonna design will be paralled to the controller board to collect data.,
I am not that much sure about the current flow.,(My be 4-20 mA)

-saif

Buffer the output of the wiper with a op amp follower so the wiper resistance will have no effect.
Hai crutschow.,
I am just a newbie to this elec. world.,

could u explain me what this is means " the wiper resistance will have no effect"?

-saif

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#### Alec_t

Joined Sep 17, 2013
13,456
my circuit deal with 3 wire RTD
I don't see why you need a 3-terminal device in an RTD circuit, or why its resistance needs to be as low as 1k. Can you post a schematic of your circuit?
As dl324 asked above, is this a school project?

#### saifudeen rizal

Joined Jun 5, 2018
50
I don't see why you need a 3-terminal device in an RTD circuit, or why its resistance needs to be as low as 1k. Can you post a schematic of your circuit?
As dl324 asked above, is this a school project?
no just doing some R&D..!for my self project
and i didnt build any circuit nor schematic yet ..!

but i have surfed internet regarding any digital pot. IC avaliability on market but none matched my need..!
-saif

#### kubeek

Joined Sep 20, 2005
5,785
I would use a set of 10,20,40,80...1280 ohm resistors in series and short each one with an opto-mos switch or analog switch if you know that the signal stays within the supply voltage.
If you need a true potentiometer and not just a variable resistor, then use this twice, so that you have for example 40 ohms on one side and 1280-40 ohms on the other.

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#### crutschow

Joined Mar 14, 2008
32,097
could u explain me what this is means " the wiper resistance will have no effect"?
That works if you need a voltage output while drawing current.
You need to better explain exactly what you need and why you are concerned about the wiper resistance.
Are you drawing current from the wiper terminal?
What will the wiper terminal be connected to?
We want to solve your problem, not what you think is the solution.

#### Alec_t

Joined Sep 17, 2013
13,456
i have surfed internet regarding any digital pot. IC avaliability on market but none matched my need.
Digikey list a 1k 8-bit pot.