Thermo Fisher Scientific ECDOTPII-S Submersible Galvanic Dissolved Oxygen Sensor - Manual (Page 2)

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HOW DISSOLVED OXYGEN SENSORS WORK
Your Dissolved Oxygen (DO) Probe is a galvanic electrochemistry device; i.e. it does not require power
from your meter or controller to generate its signal. The Sensorex DO Probe will provide a millivolt signal
proportional to the concentration of oxygen in the water. DO probes do not measure oxygen directly.
They measure the partial pressure of oxygen in the water, which is directly proportional to the percent
saturation of oxygen in the water. The concentration (mg/L or ppm) can be calculated based upon the
oxygen solubility, temperature, salinity, and total atmospheric pressure. Your Dissolved Oxygen Probe
consists of a cathode, anode, and an electrolyte separated from your process fluid by an oxygen
permeable membrane. The oxygen passing through the membrane reacts with the cathode, giving up
electrons, which produce an electrical current. A Pt 100 RTD temperature sensor is also included.
Electrical Connections
First connect the sensor to the DO instrument as follows:
DO + Red
DO - Yellow
TC+ Red, White
TC – Black
GETTING YOUR DO SENSOR READY TO USE
Remove clear wire and label from vent hole on top of DO sensor as shown in FIG 1. Discard these parts
after removing.
CALIBRATION
The simplest method to calibrate your DO sensor is in air, since air is saturated with oxygen. You may also
bubble oxygen or air. The sensor is pre-calibrated at the factory (see Specifications Section for calibration
range). If you want a 2-point calibration, a saturated solution of sodium sulfite (Na2SO3) is suggested.
17g Sodium sulfite in 125mL DI water is more than enough. Sodium sulfite will not reach a true zero
output but it should reach less than 1 mV (see Specifications Section for range).