May 26, 2008 #1 F funghome Newbie level 4 Joined Oct 15, 2006 Messages 7 Helped 0 Reputation 0 Reaction score 0 Trophy points 1,281 Activity points 1,323 adc measure resistance I want to measure an unknown resistor resistance with ADC, and calculate the unknown value using below circuit. But I don't know how to calcualate the value. LTC2410 is a 24 bits adc. If 820000 was read, what is the resistance?
adc measure resistance I want to measure an unknown resistor resistance with ADC, and calculate the unknown value using below circuit. But I don't know how to calcualate the value. LTC2410 is a 24 bits adc. If 820000 was read, what is the resistance?
May 26, 2008 #2 L laktronics Banned Joined Jan 6, 2007 Messages 942 Helped 176 Reputation 352 Reaction score 18 Trophy points 1,298 Activity points 0 how to measure resistance adc Hi, You can calculate the resistance R in K ohms as follows: REFadc = VREF+ - VREF- = Vcc - Vcc (10 + R )/ (20 + R) = Vcc [ 1- (10+R)/(20+R)] = Vcc [ (20+R-10-R)/(20+R)] = Vcc [ 10/(20+R)] Analog Input = Vcc * R/(20+R) = REFadc* (ADC Reading / ADC Full Scale) So, Vcc*R/(20+R) = Vcc[10/(20+R)] * 8,20,000 / 2^24 R = 10 * 8,20,000 / 2^24 = 0.48876 K ohms = 488.76 ohms Regards, Laktronics
how to measure resistance adc Hi, You can calculate the resistance R in K ohms as follows: REFadc = VREF+ - VREF- = Vcc - Vcc (10 + R )/ (20 + R) = Vcc [ 1- (10+R)/(20+R)] = Vcc [ (20+R-10-R)/(20+R)] = Vcc [ 10/(20+R)] Analog Input = Vcc * R/(20+R) = REFadc* (ADC Reading / ADC Full Scale) So, Vcc*R/(20+R) = Vcc[10/(20+R)] * 8,20,000 / 2^24 R = 10 * 8,20,000 / 2^24 = 0.48876 K ohms = 488.76 ohms Regards, Laktronics