V 1.1 Gravity ™ Analog Dissolved Oxygen Meter − + A Gravity DO Meter V2.0 Percent saturation only 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 DO Meter V2.0 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 = 0.3mA 3.3V = 0.3mA Absolute max ratings Parameter MIN TYP MAX Storage temperature -65 °C Operational temperature -40 °C 25 °C 50 °C VCC 3.3V 5V 5.
Operating principle The Analog Gravity™ class of meters offers the electrical engineer a low-cost solution to traditionally expensive measurements. This device gives the engineer access to the analog front end (AFE) of Atlas Scientifics Dissolved Oxygen sensing technology without the added cost that comes with complex mathematical processing. The Analog Gravity™ Dissolved Oxygen meter has been specially designed to read the voltage coming off a galvanic D.O.
Percent saturation A D.O. probe reads the partial pressure of oxygen. Using the percent saturation method, we can compare the partial pressure of oxygen in the atmosphere to the partial pressure of oxygen in the water and derive some information about its presence in the water. Because a dissolved oxygen probe can only read the partial pressure of oxygen, we are not able to determine the exact O2 content using this method. However, we can clearly determine its presence and partial pressure.
Converting the analog signal into percent saturation Every dissolved oxygen probe will output a slightly different voltage. Atlas Scientific's galvanic dissolved oxygen probe outputs ~40 – 60mV in air. = 42mV 58mV = This device can be used with a different brand of galvanic D.O. probe however, that probe may output a different voltage. The analog voltage coming off pin A is the voltage from the probe + an 11x gain. This means the analog voltage read on pin A is the voltage from the probe x11.
Connection pins Connect – to GND − + A Connect + to 3.3V or 5V Connect to analog pin / ADC Gravity DO Meter V2.0 Arduino 0 1 1 TX RX RX0 2 3 4 5 6 7 8 0 9 1 10 2 3 4 RX0 TX0 Gravity DO Meter V2.0 ) ON L TM ON ICSP TM ICSP 1 A5 A4 A3 A2 A1 ANALOG IN A0 VIN GND GND 5V RESET 3V3 IOREF POWER − + A − A5 A4 A3 A2 A1 ANALOG IN A0 GND POWER VIN GND 5V 3V3 RESET − + A IOREF A Gravity DO Meter V2.0 + Gravity DO Meter V2.
Sample code 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 sample code, a one point calibration can be performed. The calibration procedure does not use any chemical buffer solution, instead you use the open air to calibrate your probe to 100% saturation. L TX RX Arduino ON TM A5 A4 A3 A2 A1 ANALOG IN A0 VIN GND POWER Gravity DO Meter V2.
