V 2.4 Revised 12/20 Gravity ™ Analog pH Sensor / Meter − + A Gravity pH Meter V2.1 PATENT PROTECTED Written by Jordan Press Designed by Noah Press This is an evolving document, check back for updates.
Gravity dimensions 56.2mm (2.2”) − + A 24mm (0.9”) 32mm (1.2”) Gravity pH Meter V2.1 34mm (1.3”) 42mm (1.6”) Female SMA 22.3mm (0.8”) 11mm (0.4”) 6.2mm Ø (1/4”) 36UNS-2B Power consumption 5V = 3mA 3.3V = 3mA Absolute max ratings Parameter MIN TYP MAX Storage temperature -65 °C Operational temperature -40 °C 25 °C 50 °C VCC 3.3V 5V 5.
The Atlas Scientific Gravity™ Analog pH Sensor / Meter is a low-cost solution specifically designed for Students / education Proof of concept designs Moderate accuracy applications • • • Connection pins Connect – to GND − + A Connect + to 3.3V or 5V Connect to analog pin / ADC Gravity pH Meter V2.
Converting the analog signal into pH The Atlas Scientific Gravity™ Analog pH Sensor / Meter will output a voltage from 3.00V to 0.265V. Equation to convert voltage to pH Tolerance ± .015V No probe = Unpredictable 4 Gravity pH Meter V2.1 − + A Gravity pH Meter V2.1 − + A pH Volts 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 2.745 2.570 2.390 2.210 2.030 1.855 1.680 1.500 1.330 1.155 0.975 0.800 0.620 0.445 0.265 Copyright © Atlas Scientific LLC r 0.
4.00 4.00 4.00 Gravity pH Meter V2.1 Gravity pH Gravity Meter pH V2.1 Meter V2.1 − + A − + A − + A Accuracy Accuracy +/- 0.2 +/- 0.2 Life expectancy Life expectancy ~10 years ~6 – 10 months 5 Copyright © Atlas Scientific LLC r 0.
Electrical isolation The Atlas Scientific Gravity ™ Analog pH Sensor / Meter is a very sensitive device and is susceptible to electrical interference from external sources. This interference is caused by micro-voltages entering the water from unnatural sources such as pumps, solenoid valves, or other probes / sensors. When electrical interference is affecting the pH readings, it is common to see rapidly fluctuating readings or readings that are consistently off.
Calibration 0 1 3 ) RX0 4 5 6 7 8 9 10 11 12 13 DIGITAL (PWM= 2 ICSP2 TX0 RESET GND AREF Using the free downloadable arduino software, one, two or three-point calibration can be performed. The calibration procedure requires standard pH calibration buffers (pH 4, 7, and 10). Any brand of pH quality calibration buffers can be used. L TX RX Arduino ON TM A5 A4 A3 A2 A1 ANALOG IN A0 VIN GND POWER Gravity pH Meter V2.
