ModularSensors > Topics > Supported Sensors > Analog Sensors via TI ADS1x15

Analog Sensors via TI ADS1x15 topic

The Sensor and Variable objects for all analog sensors requiring analog-to-digital conversion by TI ADS1x15.

Introduction

Many sensors output simple analog voltages and leave the conversion to a digital signal and final result up to the user. These types of sensors are supported in Modular sensors by way of a Texas Instruments ADS1115 or ADS1015. The TI ADS1115 ADD is a precision, low-power, 16-bit, I2C-compatible, analog-to-digitalconverter (ADC). It is built into the EnviroDIY Mayfly. The ADS1015 is a very similar ADC with 12-bit resolution and a slightly lower price point. Both chips are widely available in Arduino-ready breakouts.

ModularSensors always uses the TI ADS1115 (also ADS1113 or ADS1114) by default, but if you wish to use a 12 bit TI ADS1015 (also ADS1013 or ADS1014) you can compile with the build flag -DMS_USE_ADS1015.

In the majority of break-out boards, and on the Mayfly, the I2C address of the ADS1x15 is set as 0x48 by tying the address pin to ground. Up to four of these ADD's be used by changing the address value by changing the connection of the address pin on the ADS1x15. The ADS1x15 requires an input voltage of 2.0-5.5V, but this library always assumes the ADS is powered with 3.3V.

Communication with the ADS1x15 depends on the soligen2010 fork of the Adafruit ADS1015 library.

Specifications

This divides the bit resolution over the range of 0-4.096V.

  • Response time: < 1ms
  • Resample time: 860 samples per second (~1.2ms)
  • Range:
    • Range is determined by supply voltage - No more than VDD + 0.3 V r 5.5 V (whichever is smaller) must be applied to this device.
    • 0 - 3.6V [when ADC is powered at 3.3V]
  • Accuracy:
    • 16-bit ADC (ADS1115): < 0.25% (gain error), <0.25 LSB (offset errror)
    • 12-bit ADC (ADS1015, using build flag MS_USE_ADS1015): < 0.15% (gain error), <3 LSB (offset errror)
  • Resolution:
    • 16-bit ADC (ADS1115):
      • without voltage divider: 0.125 mV
    • 12-bit ADC (ADS1015, using build flag MS_USE_ADS1015):
      • without voltage divider: 2 mV

Sensor Datasheet

Technical specifications for the TI ADS1115 can be found at: http://www.ti.com/product/ADS1115 For the ADS1015, see: https://www.ti.com/product/ADS1015

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