Dissolved Oxygen Sensor AM-ODO-TX – Rugged, Low-Maintenance Optical DO 

A dissolved oxygen sensor is at the heart of any water quality monitoring system, from the aeration basin of a treatment plant to a shrimp or fish pond. Dissolved oxygen (DO) drives biological treatment efficiency, animal health and the energy bill for aeration blowers.

This article introduces the AM-ODO-TX from AquaMetrix by Water Analytics – an optical DO probe with built-in digital outputs, built to keep working in harsh conditions.

What Is a Dissolved Oxygen Sensor?

Dissolved oxygen is the amount of oxygen gas held in water, measured in mg/L (ppm) or percent saturation. A dissolved oxygen sensor measures it continuously and sends the value to a controller or PLC for process automation.

Two technologies dominate the market:

• Electrochemical (Clark-type): an electrode and electrolyte sit behind a membrane. It is proven, but needs electrolyte refills, membrane cleaning and sample flow across the tip.
• Optical (luminescent): a luminescent layer coats the sensor cap. Oxygen quenches the emitted light, and the probe converts that quenching into a DO reading.

AquaMetrix has built both types for decades. The AM-ODO-TX represents its optical, low-maintenance generation.

Meet the AM-ODO-TX Optical Dissolved Oxygen Sensor

It provides two 4–20 mA outputs plus RS485/Modbus communication. The two analog outputs can carry any two of three values: percent saturation, concentration in mg/L, or temperature.

The probe connects to the AM-2300 controller, the AM-2252 controller (one output only), or straight to a PLC. See the full range of AquaMetrix controllers.

How Fluorescence Quenching Works

An LED inside the probe excites the luminescent layer on the cap. Oxygen weakens the emitted signal; the electronics measure that change, compensate for temperature, pressure and salinity, and calculate DO.

The method is self-referencing and consumes no oxygen, so it needs no warm-up and no sample flow.

Key Benefits of the AM-ODO-TX Dissolved Oxygen Sensor

• No electrolyte: no refilling or replacing fill solution.
• No flow required: stable readings even in still water.
• Self-hydrating in under 90 seconds: reliable data soon after going from dry to wet.
• Factory 90-point calibration: stored on a chip embedded in the membrane cap.
• 1–2 year cap life: low-cost replacement caps arrive pre-calibrated; snap on and go.
• Visual Lifecycle Indication (VLI): tells you when the cap needs replacing.
• More than a year between calibrations; when needed, calibrate on the controller or on the probe.
• Unaffected by CO2 and H2S, less sensitive to fouling, with salinity compensation for brackish and seawater.

The core technology behind the sensor contributed to the EPA-approved method now used as an industry standard.

AM-ODO-TX Technical Specifications

Parameter	Value
DO range	0–20 mg/L (up to 60 mg/L); 0–200 % sat (up to 600 %)
Accuracy (25 °C)	±0.1 mg/L (0–20 mg/L); ±2 % (20–60 mg/L); temperature ±0.1 °C
Resolution	0.01 mg/L; 0.01 °C
Response time	T90 < 45 s; T95 < 60 s
Operating temperature	–5 to 50 °C (storage –40 to 65 °C)
Max depth / pressure	210 m (689 ft); 150 psi (0–50 °C)
Salinity & pressure compensation	Fixed or real-time
Outputs	Dual 4–20 mA (sourcing); RS485/Modbus
Power	8–36 VDC; 0.6 W max @ 12 VDC
Wetted materials	cPVC body, PC/ABS, PPS, PC/PMMA
Ingress protection	IP68
Mounting	1" MNPT both ends; length 7.6"
Cable	15 ft standard, custom lengths available

Optical vs. Electrochemical Dissolved Oxygen Sensor

Criterion	Optical (AM-ODO-TX)	Electrochemical (Clark)
Electrolyte	None	Yes, replaced periodically
Sample flow	Not required	Usually required for stable readings
Start-up	Under 90 s, no warm-up	Needs polarization time
H2S interference	None	Electrode can be poisoned
Main maintenance	Cap every 1–2 years	Membrane, electrolyte, electrode cleaning

Dissolved Oxygen Sensor Applications

• Municipal wastewater and sewage: control aeration blowers by DO and cut energy use.
• Industrial wastewater: continuous monitoring that tolerates H2S.
• Aquaculture and fish farms: low-oxygen alarms and aerator control, with salinity compensation for brackish ponds.
• Boilers: track dissolved oxygen in feedwater.
• Horticulture: manage oxygen in hydroponic nutrient solutions.

Installation and Maintenance

With 1" MNPT threads on both ends, the probe mounts submerged, in-line or via hot-tap insertion. Accessories include the AM-ARM-5 submersion kit, AM-TEE-R5 2" CPVC tee, AM-HTA-R5 ball-valve hot-tap assembly, AM-JB2 junction box and extension cable.

Maintenance comes down to rinsing the cap and swapping it when the VLI signals. Store the probe with the AM-ODO-TX-CAL calibration/storage cap.

For a complete monitoring station, pair it with pH sensors, ORP sensors and conductivity sensors.

FAQ

Can the AM-ODO-TX dissolved oxygen sensor work in saltwater? Yes. It supports fixed or real-time salinity compensation.

How often is the membrane cap replaced? Typically every 1–2 years; the VLI indicates when.

Does a new sensor need calibration? No. Caps ship with a factory 90-point calibration, and recalibration intervals exceed one year.

Conclusion

If you need a dissolved oxygen sensor that is accurate, rugged and nearly maintenance-free, the AM-ODO-TX deserves a close look. Contact [Company name – phone] for configuration advice and a quote.