Berroa Ferenc
New Member
First of „Happy New Year” to ALL of you.
Please, help me understand an electrical and mathematical problem.
I’m working in a remote input/output module, and when I measure an unknow resistance with a digital ohmmeter I get 17% greater value than reading it with the ADC of the microcontroller.
I use a potential divider to know the resistance in this way:
5V---|Reference resistance|---ADC---|Unknow Resistance|---GND
Reference resistance = 10K
The mathematical equation I use is:
V_ADC = (ADC value * (5V / 1023))
Resistance = ((V_ADC / 5V) * Reference resistance) / (1 - (V_ADC / 5V))
I would like to know your opinion about this. The digital multimeter is an standard one.
The resistance I’m measuring is 1K with 20% tolerance.
The other problem is that resitance reading is not linear because the non linearity of the ADC reading. Any one can give me an idea?
Thank you in advance.
Cordially: Berroa Ferenc.
Please, help me understand an electrical and mathematical problem.
I’m working in a remote input/output module, and when I measure an unknow resistance with a digital ohmmeter I get 17% greater value than reading it with the ADC of the microcontroller.
I use a potential divider to know the resistance in this way:
5V---|Reference resistance|---ADC---|Unknow Resistance|---GND
Reference resistance = 10K
The mathematical equation I use is:
V_ADC = (ADC value * (5V / 1023))
Resistance = ((V_ADC / 5V) * Reference resistance) / (1 - (V_ADC / 5V))
I would like to know your opinion about this. The digital multimeter is an standard one.
The resistance I’m measuring is 1K with 20% tolerance.
The other problem is that resitance reading is not linear because the non linearity of the ADC reading. Any one can give me an idea?
Thank you in advance.
Cordially: Berroa Ferenc.