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ADS1115: PROBLEM ABOUT TAKING 16 BIT RANGE

Sagar Saini
Prodigy 10 points
Part Number: ADS1115
Other Parts Discussed in Thread: ADS122C04, ADS1219

Greetings,

                 I need a urgent help about ADS1115 ADC  Resolution ,when i used  single ended mode i get range up to 32767 after increasing the gain which is also mentioned in the datasheet. but i need 16 bit resolution                     65535 . i have also used differential mode  but din't get the range 65535. For the differential mode i gave 2.5 volt on channel  AIN1_AINn and  and Reading the Channel  AIN0 with respect AIN1. Please help                     me how can i get the 16 bit full range 0-65535,and which reference voltage should i give to  AIN1. My supply voltage is 5 volt.

                Thanks 

  • 0
    TI__Guru** 113765 points

    Hi Sagar,

    Welcome to the E2E forum! The ADS1115 outputs the conversion result in binary 2's complement.  In short, half of the full-scale range is positive and have is negative as the input is differential.  Measurements referred to ground will only use 1/2 of the full-scale range.

    To utilize more of the range, you are on the right track in that you will need to measure the input with respect to another voltage.  However, the full-scale range (FSR) of the ADS1115 does not have +/-2.5V range.  There is a +/- 2.048V and +/- 4.096V range.  So if 0 to 5V is your measurement range, then you will not be able to utilize all 16 bits anyway.

    So what voltage range will you be measuring?  Have you considered using a different device that allows for an external reference?  You could use a 24-bit device to increase the measurement resolution by using the ADS1219 or the ADS122C04.  Both of these devices are I2C.  You will still see a similar issue as the input is differential and you will only be able to utilize the positive range when directly measuring the input with respect to ground.  However, as the ADC resolution is higher, the measurement can achieve better measurement resolution as compared to the 16-bit device.

    Best regards,

    Bob B