# Analog Sensor Board The SmartCitizen Analog Sensor Board (_ASB_) is an expansion board for the Smart Citizen Kit that provides connectivity to analog sensors with a high precission ADC (Texas ADS1115) via I2C, with four configurable addresses. It also gives the possibility to directly hook up [this ADC by Adafruit](https://www.adafruit.com/product/1085). We use it to measure analog voltages from low power sensors such as the [Alphasense Ltd.](https://www.alphasense.com/) [electrochemical](https://docs.smartcitizen.me/knowledge/air/chemical/Alphasense_Electrochemical.md) sensors, or [SPEC](https://www.spec-sensors.com/) sensors. You can use it in different configurations and the different headers:  Below you see a comparison: === "B-series sensors" === "A-series sensors" === "Empty" ## Features The **Analog Sensor Board** features two [TI ADS1115](https://docs.smartcitizen.me/knowledge/other/TI_ADS1X15.md) 16bit 4-channel ADCs, and can read 8 analog channels in total. It has a potential to read up to 16 channels by daisy chainning two boards (by changing the address with the selectable jumper), or many more if you use a multiplexer. Check the [ADS1115 knowledge page](https://docs.smartcitizen.me/knowledge/other/TI_ADS1X15.md) for details on how the firmware reads the ADCs. !!! info "Previous version" A previous version could interface 4 channels, daisy chainable up to 4 boards - with a total of 16 analog channels, by using [Adafruit ADS1115 Breakout board](https://www.adafruit.com/product/1085). Below you have a functional diagram: {:style="width: 450px"} The **Analog Sensor Board** natively operates at 3.3V, but can work up to 5.5V with a selectable jumper through a step-up converter (RECOM 0309S), making the digital voltage consistent with the sensor measurement voltage. To make everything consistent, it integrates a level-shifter from the GROVE connector's voltage to the internal voltage. Digital communications, via the Grove port, is done via I2C, from 3.3V up to 5.5V. ## Design files You can find all the design files for the different versions of the **Analog Sensor Board** in the [hardware repository](https://github.com/fablabbcn/smartcitizen-analog-sensor-board). Check the design files