# ADS1115 issue while taking results

#### RenesasTaac

Joined Dec 26, 2016
2
Hello Everyone,

I am facing an issue with ADS1115 ADC which is 16 bit ADC. I am able to communicate mircocontroller and ADC. I am even able to get the ADC counts. Though counts are fluctuating I have used averaging method to get proper counts.

The PGA is +/- 2.048. I am using channel 0. I am getting below results,

200 200

300 300

1000 1000

1024 1024

1058 1058

To convert ADC count into voltage I am dividing ADC count by 1000. My question is how to get fourth digit after decimal point.

Suppose mV=1058.5 I need converted value should be 1.0585.

As the ADC is 16 bit, can anyone please explain me how to get fourth digit after the decimal point.

#### ericgibbs

Joined Jan 29, 2010
13,242
hi RT,
What is the input voltage range [max] to the 16 bit ADC.?
E

EDIT:
Have you considered multiplying the ADC input voltage by 10, using a OPA.?

Last edited:

#### ebeowulf17

Joined Aug 12, 2014
3,282
Are you sure you don't have an ADS1015?

Sounds like a silly question, but the numbers match perfectly. A 12 bit ADC yields 4096 values, so with the PGA set for +/-2.048V input range, each bit corresponds with 1 mV, which perfectly matches your readings.

Your current behavior is exactly what would be expected from a 12 bit ADC, but is totally inexplicable (at least to me) with a 16 bit ADC.