Diagram Of "Lab Built" Dissolved Oxygen Probe & Alcohol Probe

Diagram Of A Lab Built Dissolved Oxygen Probe And Alcohol Probe

The staff at CEBTech Services has helped design and build many process sensors for the measurement of concentrations of various alcohols, and dissolved oxygen.

On the farthest left is a basic design for a galvanic dissolved oxygen probe used widely in Bioscience. They are inexpensive and relatively easy to build. They are steam sterilizable, stable, and have a linear millivolt electrical output range of 0-25 mv. They perform with the over-all electrochemical reactions as follows:

SILVER CATHODE: 1/2 O2 + H2O + 2e- ___> 2OH -

LEAD ANODE: Pb ___> Pb++ + 2e-

ANODE SURFACE: 1/2O2 + Pb + H2O ___> Pb(OH)2

(Electrolyte composition: Acetic acid 5.0 M, Sodium acetate 0.5 M, Lead acetate 0.1 M, pH 3.0)

On the right is one of the many designs for steam sterilizable alcohol probes. This design has a constant flow of low-pressure air flowing through it and through the silicone tubing which is very permeable to alcohols. The air absorbs alcohols proportional to that present in the fermentation broth. The air/alcohol mix is then sent to a gas sensor with an electrical output, 2-20 VDC, such as the Model TGS822 made by Figaro USA, Inc. www.figarosensor.com.

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Two Finished O2 Probes

View of Two Finished Galvanic Dissolved Oxygen Probes

These are two completed galvanic dissolved oxygen probes. They are steam sterilizable "in place" in a bioreactor. They are mounted in 316 stainless steel housings to withstand turbulence and to allow pressure compensation. The probe tips extend out of the housing approximately 5 cm to allow replacement of the teflon membrane (32, 136, 195, 199, 226).

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Craig Bremmon
CEBTech Services
503 11 th Ave. SE, Suite 5
Aberdeen, SD 57401

Phone: 605 226-3595
Mobile: 605 377-4062
Fax: 605 226-3595