Measuring an output voltage within a simple circuit does not match the calculation

Thread Starter

arhzz1

Joined Oct 21, 2020
22
Hello! So I'm facing kind of a problem right here. Im susposed to build this circuit

Snimka zaslona 2020-12-05 145029.png

Now the resistors im using are 1k and 2.2k Ohm, and the input voltage we need to set to 3V,over a GUI that we are executing over python.Now I've connected everything to my PC and whenI measure the outpot voltage I get around 2,9V.This doesnt seem right to me. I've done the calculation per hand like this (3V * 2.2)/ (R1+R2). And I get around 2,06V. Now I'm 99% sure I've done everything right,and still my measerument is way off.Here is how it looks

20201205_145530.jpg

Can anyone tell me what I'm doing wrong? Thank you in advance!
 

Dodgydave

Joined Jun 22, 2012
9,951
Bad contacts..

You should be getting around 1V, put the Resistors into the supply feeds directly and twist the ends together with the ADC feed wire to make sure of a better connection.

Do yo have a DVM ?
 

bertus

Joined Apr 5, 2008
21,364
Hello,

Are you trying to measure the DAC output via a voltage divider with the ADC?
In your drawing the 2K2 is at the top and the 1K at the bottom.
DAC to ADC.png
Bertus
 

ronsimpson

Joined Oct 7, 2019
1,227
Using the picture from bertus, you should have about 2V across the top resistor and about 1V across the bottom resistor. Maybe you wanted to switch the two resistors.
 

bertus

Joined Apr 5, 2008
21,364
Hello,

When you get the same result with swapping the resistors, there must be a bad contact.
Also check the program to measure the voltage.
Try to make the circuit on a different part of the breadboard.

Bertus
 

Thread Starter

arhzz1

Joined Oct 21, 2020
22
Hello,

When you get the same result with swapping the resistors, there must be a bad contact.
Also check the program to measure the voltage.
Try to make the circuit on a different part of the breadboard.

Bertus
Okay will do, but what exactly is a bad contact?
 

Thread Starter

arhzz1

Joined Oct 21, 2020
22
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