Gravity: KnowFlow Basic Kit - DIY Water Monitoring Kit with pH & EC Sensors
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Description
The Gravity: KnowFlow Basic Kit is an open-source automated water monitoring platform designed for environmental researchers, educators, and citizen scientists. Built around an Arduino-compatible Bluno microcontroller with integrated Bluetooth, it continuously tracks and logs water pH and electrical conductivity.
Arduino and Bluetooth processing core
The system is powered by a Bluno development board combining an ATmega328P microcontroller with an onboard Texas Instruments CC2540 BLE chip. It supports transparent serial communication and wireless programming, enabling real-time sensor visualisation on smartphones without physical tethering.
Accurate pH and conductivity sensing
The kit includes an analog pH sensor offering a 0 to 14 pH range with plus-or-minus 0.1 pH accuracy at 25 degrees Celsius and an onboard calibration potentiometer. The companion electrical conductivity probe measures from 1 to 20 mS/cm with plus-or-minus 10 percent full-scale accuracy on a standard 10-bit ADC, ideal for freshwater and moderate salinity testing.
Isolated analog signal path
A dedicated Gravity analog signal isolator decouples sensor power from the Bluno microcontroller. This reduces electrical noise and safeguards the controller against potential electrical faults in wet testing environments.
Autonomous timestamped data logging
Sensor readings are paired with exact timestamps via an I2C SD2405 real-time clock module and written directly to the included 16GB Class 10 microSD card. The entire logging rig can run independently in the field using either USB or an external 7V to 12V DC power supply.
Modular Gravity expansion
Fitted with a Gravity IO Expansion Shield V7.1, the platform enables quick plug-and-play integration of additional sensors such as dissolved oxygen, ORP, or waterproof DS18B20 temperature probes. All hardware schematics and pre-loaded firmware are open-source, allowing seamless adaptation for advanced IoT and cloud-connected projects.
Downloads & documentation
Specifications
| Microcontroller | Atmega328p with Arduino Uno bootloader |
| Bluetooth chip | TI CC2540 (onboard BLE) |
| Wireless programming | Supported via BLE |
| BLE configuration | AT command set support |
| Serial communication | Transparent mode |
| Firmware update | Over-the-air upgrade capability |
| Power supply | USB or external 7V–12V DC |
| Board dimensions | 60mm × 53mm (2.36" × 2.08") |
| Board weight | 30g |
| pH sensor operating voltage | 5.00V |
| pH sensor dimensions | 43mm × 32mm (1.69" × 1.26") |
| pH measurement range | 0–14 pH |
| pH accuracy | ±0.1 pH (25°C) |
| pH response time | ≤1 minute |
| pH connector | BNC with pH2.0 interface (3-pin SMD) |
| pH calibration | Gain adjustment potentiometer |
| pH indicator | Power LED |
| EC sensor operating voltage | 5.00V |
| EC sensor dimensions | 45mm × 32mm (1.77" × 1.26") |
| EC measurement range | 1–20 mS/cm |
| EC operating temperature | 5–40°C |
| EC accuracy | ±10% F.S (with Arduino 10-bit ADC) |
| EC interface | PH2.0-3P with BNC connector |
| EC electrode constant | K=1 |
| EC electrode cable length | approximately 60cm (23.62") |
| EC power indicator | LED |
| Analog signal isolator operating voltage | 5.0V |
| Analog isolator response time | 4 seconds (typical) |
| Analog isolator error (both ends) | ±20mV (typical) |
| Analog isolator interface | PH2.0-3P |
| Analog isolator no-load current | 75mA |
| Analog isolator dimensions | 42mm × 32mm (1.65" × 1.26") |
In the box
| Bluno (DFR0267) | 1 |
| Gravity: Analog pH Sensor / Meter Kit For Arduino (SEN0161-V2) | 1 |
| Gravity: Analog Electrical Conductivity Sensor / Meter For Arduino (DFR0300) | 1 |
| Gravity: IO Expansion Shield for Arduino V7.1 (DFR0265) | 1 |
| Gravity: I2C SD2405 RTC Module (DFR0469) | 1 |
| MicroSD card module for Arduino (DFR0229) | 1 |
| Gravity: Analog Signal Isolator (DFR0504) | 1 |
| SD/MicroSD Memory Card (16GB Class10 SDHC with Adapter) (FIT0394) | 1 |
| Analog sensor cable | 2 |
| Digital sensor cable | 1 |
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