How to Measure Dissolved Oxygen in Liquids

The post discusses a sensor device used for measuring the level or amount of dissolved oxygen in water and other fluids. The idea was requested by Mr. Amit

Technical Specifications 

I didn't find sensors or sensor modules for Dissolved Oxygen or pH readings for us to use with controllers for our projects. but we get sensors with controllers with display which are expensive.

Do you have any idea?

Thanks

Analyzing the Circuit Query

Sensors for measuring dissolved oxygen are available ready made in the market, one such example may be seen below:

The output can be easily integrated with an external amplifier circuit for the required conversions or displays.

If possible I'll try to update the info in my blog soon with all the details.

The Design

Today companies manufacture numerous types of sensors for measuring oxygen in water known as Dissolved Oxygen sensors, which you can use in water, chemical processor jobs, laboratory, and ecological .Dissolved oxygen (DO) is the expression or the evaluation of the oxygen dissolved in a unit volume of water, generally in units of mg/L or ppm.

The preferred sensing unit may comprise of 2 electrodes, an anode and cathode, in electrolyte and from the water in question by an oxygen permeable membrane, as observed in Figure 2.

Oxygen diffuses across the membrane and interacts with the cathode to a potential difference proportional to the oxygen diffused into the sensor.

DO sensors consequently basically determines the deficient strain of the oxygen in water; permits extra oxygen to across the membrane and more voltage to be generated. The current is then converted into a millivolt output, that could be assessed with a WSN wireless node.

The type of dissolved oxygen sensor shown above are quite ideal since the output can be quickly accessed and interfaced with any desired measuring instrument such as a millivoltmeter, LED bar graph meter, transistorized amplifier, opamp based amplifier etc for translating the collected data into the the required levels so that it can be assessed appropriately for the results.

The internal view of the above example sensor may be witnessed in the following image:

Sensor Setup

The shown outputs provides a direct readable data in the form of millivolts which could be used for for triggering an external electronic circuit stage.