Gravity: Analog pH Sensor V2(PRO)

This article offers a comprehensive guide to calibrating and measuring pH using Arduino, featuring example code and essential maintenance tips for optimal sensor performance.

How to build and calibrate an Arduino hydroponic pH monitoring system with Gravity sensors and DS18B20 temperature compensation. It’s like setting up a digital lab assistant that continuously watches nutrient solution health. The guide targets makers and growers using DFRduino UNO R3, SEN0169-V2 pH sensor, DS18B20 waterproof temperature probe, and the DFRobot_PH Arduino library. Hardware prep covers pH probe, analog and digital Gravity cables, buffer solutions at pH 4.0 and 7.0, and proper wiring via an IO expansion shield. Software prep requires Arduino IDE 1.0.x or 1.8.x and installing the DFRobot_PH library from GitHub, then uploading sample sketches that read analog voltage on A1, convert it to pH with temperature compensation, and print temperature and pH to the serial monitor every second. Two-point calibration is performed monthly or after long storage: rinse the probe, stabilize in pH 7.0 buffer, send “enterph”, then “calph”, then “exitph” over serial; repeat the same sequence in pH 4.0 buffer so the library auto-recognizes each solution and stores calibration parameters in EEPROM. Safety and accuracy tips emphasize keeping the BNC connector and signal conversion board dry, mounting the board off wet or conductive surfaces with nylon pillars, and protecting the fragile glass bulb from impact and scratches. For automatic temperature compensation, a DS18B20 on digital pin 3 is read via OneWire, with robust checks on CRC, device family code, conversion timing, and valid temperature range, falling back to 25 °C if readings are out of bounds. Maintenance notes explain that new or long-idle probes must be soaked in 3 mol/L KCl for 8 hours, stored with moist KCl in the protective cap, and never shorted or immersed long-term in distilled water, proteins, fluoride acid, or silicone oil. For aged or contaminated probes, the text details expert-level rejuvenation: brief 4% HF treatment, extended 0.1 mol/L HCl soaking, and tailored cleaning based on contaminant type, while warning that solvents like carbon tetrachloride or trichloroethylene can permanently damage the glass surface. Overall, the content bridges curiosity to hands-on deployment by giving complete wiring, code, calibration commands, and lab-grade care procedures, positioning DFRobot’s Gravity ecosystem as a reliable path to precise, long-term hydroponic pH and temperature monitoring.

How to build a UNIHIKER K10 hydroponic pH and temperature monitor: prepare the Gravity analog pH sensor SEN0169-V2, DS18B20 temperature kit, PH2.0 cables, and install Arduino IDE plus the DFRobot_PH library, then wire the pH output to P0 and DS18B20 data to P1 according to the wiring diagram. It’s like giving your hydroponic tank a smart thermometer and pH meter that report to a mini touchscreen computer. Before first use or monthly, perform two‑point calibration with pH 7.0 and 4.0 buffer; rinse the probe with distilled water between solutions, stabilize in pH 7.0, enter serial commands enterph, calph, then exitph to store parameters, and repeat the same sequence in pH 4.0 so the library saves both points to EEPROM for accurate readings. The calibration example code uses PH_PIN P0, reads ADC voltage every second, optionally calls readTemperature for compensation, and uses ph.readPH plus ph.calibration with serial commands to adjust slope and offset. The K10 demo sample integrates the UNIHIKER_K10 screen, OneWire DS18B20, and DFRobot_PH: it reads DS18B20 temperature, falls back to 25 °C if the sensor fails, converts ADC counts to millivolts using ADC_MAX 4095 and Vref 3300 mV, then calls ph.readPH(voltageMv, temperatureC) and prints temperature, voltage, and pH to the serial monitor while also drawing them on the K10 canvas. Users see live updates every second, including a “Comp: pH(T) enabled” line that confirms temperature compensation is active, making it ideal for classroom demos or DIY nutrient monitoring. To protect measurement accuracy, keep the BNC connector and signal conversion board dry, mount the board on nylon pillars away from wet or conductive surfaces, and avoid any impact on the fragile glass bulb at the probe tip. After each measurement, unplug the probe from the board if power is off, store the tip in 3 mol/L KCl inside the protective cap to keep the glass hydrated, and never leave the probe long‑term in distilled water, protein‑rich solutions, acid fluoride, or silicone oil. For long‑term drift or reduced slope (slow, unstable readings), clean the sensing end according to contamination type; in severe cases, briefly etch in 4% HF for 3–5 seconds, rinse, soak in 0.1 mol/L HCl for a few hours, then rinse with deionized water, while avoiding aggressive polycarbonate‑soluble cleaners such as carbon tetrachloride or trichloroethylene that can permanently damage the glass surface.