ADS1115: Check for rated requirement

Hi Adrian,

Both the ADS1115 and the ADS112C04 are suitable ADCs for this type of application. 

The ADS1115 is a smaller part, but the ADS112C04 would give you better noise performance. 

Using a K-type thermocouple you can expect to see around 16 mV at 390°C and -1.15mV at 30°C. This means you need 4200 counts for around 17.15mV to achieve 0.1 deg C of resolution. 

That means around approximately a 4uV difference per count to measure 0.1 deg C in that temperature range. 

You can take a look at the Noise in μVRMS and μVPP for both of these parts in the data sheet to compare the noise performance you would get. 

The ADS112C04 at a gain of 64 and 45SPS noise level would be at around 0.98uV, which is lower than 4uV needed to achieve your resolution, so this part would meet the requirements. 

ADS112C04

ADS1115

Lower SPS generally yield less noise in the measurement because the delta-sigma ADC achieves a higher OSR when the output data rate is lowered. 

By increasing the OSR, and thus reducing the output data rate, the noise performance of the ADC can be optimized. In other words, the input referred noise drops when reducing the output data rate because more samples of the internal modulator are averaged to yield one conversion result. Increasing the gain also reduces the input-referred noise, which is particularly useful when measuring low-level signals

This Application note shows how to make temperature measurements with an ADC and sensor and uses the ADS1115 as an example Ultra-Small, Precision Analog Temperature Sensor Measurement With ADC (Rev. A) (ti.com). Hope you find this useful.

Best Regards,

Angel