Oxygen Sensor for Laboratory Series

ACITEK G300 Online DO Transmitter + DO6800 High-temperature Dissolved Oxygen Electrode

1. Project Background
A fine chemical enterprise produces 50,000 tons of acrylate annually. Its reaction kettles operate at 80–120℃ and 0.6–1.0 MPa. Dissolved Oxygen (DO) must be strictly controlled within 0.5–1.5 mg/L. Excess DO causes side reactions and reduces product purity, while insufficient DO leads to incomplete chemical reaction and lower output.

The traditional polarographic electrodes suffered severe signal drift above 60℃, with membranes aging every 2–3 weeks. Frequent shutdown for calibration and replacement brought high maintenance costs and disrupted continuous production. The site adopted ACITEK G300 DO Transmitter + DO6800 High-temperature DO Electrode to solve the problems.



2. Product Specifications
ACITEK G300 Online DO Transmitter

Measuring range: 0.00–40.00 ppm, Accuracy: ±0.01 ppm
Working temperature: -10.0–130.0℃, automatic temperature compensation
Output: 4-20mA & Modbus RTU, compatible with DCS system
Protection class: IP65, explosion-proof design







ACITEK DO6800 High-temperature DO Electrode

Temperature resistance: 0–130℃, supports 130℃ SIP sterilization
Housing: 316L stainless steel, acid & alkali resistant
High-temperature resistant membrane, anti-aging and anti-fouling
Response time: t90 ≤ 60 s




3. Installation & Commissioning

Mounted on DN50 side port of reaction kettle, immersed 20–30 cm below liquid level, away from agitator and inlet to avoid bubble interference.
Shielded cabling to prevent electromagnetic interference.
Two-point calibration with oxygen-free water and air-saturated water. Stable performance lasts over 6 months after one calibration.
Linked with DCS: Automatic nitrogen purge when DO below set value; cut off nitrogen supply when DO exceeds limit.

4. Application Results (6-month operation)

Stable measurement: No signal drift at 120℃, DO fluctuation controlled within ±0.1 mg/L.
Low maintenance: Membrane service life extended from 2–3 weeks to 8–10 months. Calibration cycle reaches 6 months, maintenance workload reduced by over 70%.
Quality improvement: Acrylate purity rose from 99.2% to 99.7%, high-grade product rate increased by 12%.
Higher efficiency: Gas consumption cut by 18%. Shutdowns caused by DO faults were eliminated, with annual output increased by 2000 tons.
Durable performance: Continuous trouble-free operation for 180 days, no corrosion orscaling on electrode.

5. Customer Feedback
"This high-temperature DO monitoring solution perfectly solves our pain points of unstable reading and frequent maintenance. The G300 transmitter delivers reliable data and smooth communication. The DO6800 electrode works well under high temperature. It greatly guarantees our continuous production and product quality." — Manager Wang, Equipment Department

6. Applicable Scenarios

Chemical industry: High-temperature reaction kettles, polymerization & oxidation processes, high-temperature wastewater
Pharmaceutical industry: Fermenters with 121℃ SIP sterilization
Power industry: Boiler feed water and condensed water trace oxygen monitoring
Environmental protection: High-temperature industrial wastewater & leachate treatment

Case 1: Thermal Power Plant Boiler Feed Water & Condensate Monitoring
Project Background
A 2×300MW thermal power plant in East China needs full-process monitoring of deaerator outlet feed water, condenser condensate and boiler drain water. Per national power industry standard DL/T 502.29-2019, tiny ion impurities in water will cause boiler scaling and turbine blade corrosion, which may trigger unplanned shutdown and huge economic loss. The original old conductivity sensors had two pain points:


Ordinary 304 stainless steel electrodes corroded rapidly under chloride-containing condensate, measurement drift occurred within 3 months;
Non-standard thread fittings required customized welding bases, high installation cost and difficult later disassembly maintenance.

ACITEK Solution Deployment

Sensor selection: AC58031404 SS316L 2-electrode conductivity sensor (K=1cm⁻¹), 3/4NPT male thread directly matched with pipeline standard 3/4NPT tee joint, no extra custom fittings;
Installation layout: Installed on condensate sampling pipeline, boiler feed water outlet and blowdown pipeline via side pipeline insertion; 44mm insertion length ensures electrode fully immersed in stable fluid, avoiding bubble interference;
System matching: Paired with ACITEK G100 compact DIN rail transmitter, 4-20mA active signal access plant DCS system, RS485 Modbus upload data to SCADA platform; built-in PT1000 automatic temperature compensation eliminates temperature drift error of high-temperature water samples;
Working condition adaptation: SS316L material resists trace chloride ion corrosion in condensate, withstands 17bar working pressure and 90℃ sampling water temperature.

On-site Operation Effect

Measurement stability: After 12 months continuous operation, measurement deviation is always within ±1% (0.02~5000µS/cm) and ±3% (>5000µS/cm), no regular calibration drift phenomenon;
Maintenance cost reduction: Replace cycle extended from 3 months to 12 months, only quarterly simple surface cleaning is needed, saving 70% of annual sensor replacement labor & material cost;
Safety optimization: Real-time conductivity abnormal linkage alarm timely reminds resin regeneration and condenser leakage risk, boiler scaling failure rate decreased by 8%, annual power generation loss risk reduced greatly.

Case 2: Semiconductor Factory Ultrapure Water (UPW) Preparation Line Monitoring
Project Background
A wafer manufacturing enterprise in Shanghai built a 18.25MΩ·cm ultrapure water production line, requiring real-time monitoring of RO reverse osmosis effluent, EDI terminal ultrapure water and cleaning circulating water. The core demand is to capture tiny conductivity rise caused by membrane element damage or ion exchange resin failure, to avoid wafer etching pollution and mass product scrap.

Application Scheme & Configuration

Sensor matching logic: K=1cm⁻¹ wide-range electrode fits full-process water quality monitoring—low-conductivity ultrapure water (0.05~2µS/cm) and medium-conductivity intermediate circulating water (500~5000µS/cm) can be measured by one sensor model, reducing spare parts types;
Installation method: Adopt flow cell pipeline installation, 3/4NPT thread quickly connect small-bore flow cell, compact structure fits narrow space of ultrapure water equipment rack;
Signal transmission: 5m shielded cable anti-electromagnetic interference in clean workshop, matched G100-DIN rail transmitter centralized installed in small control cabinet, multi-point conductivity data unified upload to water treatment PLC;
Customization support: Factory customized 10m long cable for remote sampling points according to workshop layout, realizing unified sensor model for all monitoring positions.

Actual Benefit

Early warning capability: Quickly capture conductivity fluctuation of 0.1µS/cm, advance 3~5 days to judge EDI resin failure, avoid batch wafer contamination loss;
Cost optimization: Single sensor covers all water quality sections, no need to prepare multiple electrode constants for different process sections, spare parts inventory cost cut by 45%;
Stable long-term operation: SS316L electrode will not release metal ions into ultrapure water, meet semiconductor high-purity water monitoring requirements, one-year warranty provides stable after-sales guarantee.

Case 3: Fine Chemical Plant Reaction Kettle & Circulation Cooling Water Monitoring
Project Overview
A fine chemical factory producing pharmaceutical intermediates has multiple reaction kettles and cooling water circulation systems. It needs to monitor electrolyte concentration in synthesis liquid and circulating water conductivity to control reaction conversion rate and prevent pipeline scaling blockage. The medium contains weak organic acid and trace chloride, putting forward high corrosion resistance requirements for electrodes.

ACITEK Deployment Plan

Tank & dual pipeline installation: Reaction kettle side wall 3/4NPT thread interface for sensor insertion; cooling water main pipeline symmetrical installation two sensors to monitor inlet & outlet conductivity;
Material advantage: SS316L electrode effectively resist weak acid and chloride corrosion, compared with plastic-shell electrodes, it is not easy to deform and aging under 80℃ circulating water long-term soaking;
Control linkage: 4-20mA signal feeds back to reaction PLC, automatically adjust raw material feeding amount according to solution conductivity; cooling water conductivity high value triggers automatic dosing & blowdown control to reduce scaling;
Maintenance convenience: Standard 3/4NPT thread can be directly screwed out without stopping production for short-term replacement cleaning, greatly improving production continuity.

Site Feedback

Reaction yield improved: Stable real-time conductivity data optimizes feeding control, intermediate product yield increased by 12%;
Pipeline maintenance cycle extended: Timely cooling water blowdown control reduces scaling frequency, pipeline cleaning cycle from 1 month extended to 4 months;
Wide range adaptability: One sensor continuously measures synthesis liquid (1000~20000µS/cm) and cooling water (50~800µS/cm), equipment procurement cost reduced.

Case 4: Small Factory Sewage Treatment Station Discharge Water Monitoring
Demand Background
Multiple small chemical & food processing factories built decentralized sewage treatment stations, needing online conductivity monitoring of aerobic tank effluent and final discharge water to meet environmental protection real-time upload requirements. The on-site cabinet space is narrow, with limited maintenance manpower, requiring low-cost, easy-to-install & low-maintenance conductivity measurement solution.

Matching Solution

Low-cost integrated system: AC58031404 conductivity sensor + G100 ultra-narrow DIN rail transmitter (12.5mm width), multiple sets side-by-side installed in small control box without cabinet reconstruction;
Immersion installation: 3/4NPT thread matched with stainless steel mounting sleeve, directly put into sewage outlet weir tank, 44mm insertion length avoids sludge sediment coverage at tank bottom;
Signal output dual mode: 4-20mA analog signal access environmental protection data collector, RS485 remote data upload to factory cloud platform, realize unattended monitoring;
Adapt to wastewater medium: SS316L anti-corrosion electrode resists sewage weak acid & alkali medium, not easy to be corroded by organic sewage.

Operation Results

Meet environmental compliance requirements: Continuous 24h online conductivity data meets local environmental bureau monitoring upload standards, no penalty risk due to missing monitoring data;
Labor saving: Only quarterly simple cleaning of electrode surface sludge, no frequent calibration, suitable for unattended small sewage stations;
Space saving advantage: Ultra-thin transmitter + compact sensor solves the problem of small control box insufficient installation space, overall equipment investment reduced by 30% compared with split large display conductivity meters.

Core Product Advantages Reflected in All Cases

Universal 3/4NPT standard thread: Compatible with all industrial pipeline, tank, flow cell common interfaces, no customized fittings, low installation cost and fast construction;
SS316L all wetted material: Excellent corrosion resistance to chloride, weak acid, weak alkali medium, long service life in power, chemical, semiconductor, wastewater industries;
K=1cm⁻¹ ultra-wide measurement range (0.02~50000µS/cm): Cover ultrapure water, intermediate process water, high-salinity sewage, one model for multi-scene use, reduce spare parts inventory;
Built-in PT1000 temperature sensor: Automatic temperature compensation, eliminate measurement error caused by medium temperature change, stable data under high/low temperature working conditions;
Flexible cable customization: Standard 5m cable, support OEM/ODM customized length to adapt long-distance sampling points;
Perfect matching ACITEK G100 DIN rail transmitters: Form compact low-cost online conductivity monitoring system, 4-20mA + RS485 dual signal output, compatible with all mainstream PLC/DCS industrial control systems;
Pressure & temperature resistance: Max 17bar (250psig) pressure, 93℃ medium temperature, adapt high-temperature & high-pressure industrial water sampling pipelines.

Summary
ACITEK AC58031404 SS316L 2-electrode conductivity sensor breaks the limitation of single-scene electrodes. With standard 3/4NPT thread, wide measurement range and reliable corrosion-resistant material, it has formed mature, low-cost and stable monitoring schemes in power, semiconductor, fine chemical and wastewater treatment industries. Whether it is high-standard ultrapure water precision monitoring, high-temperature high-pressure power plant water sampling, corrosive chemical process liquid control or decentralized sewage environmental monitoring, this sensor can meet on-site measurement demands, and combined with ACITEK G100 series compact transmitters, it provides users with space-saving, easy-maintenance and customizable industrial water conductivity full-set measurement solutions.

Updated Environmental Regulations Bring New Compliance Requirements for Wastewater Online Monitoring Equipment


With the official implementation of China’s HJ 212-2025 Technical Requirements for Data Transmission of Pollutant Automatic Monitoring System and the upcoming enforcement of the Ecological Environment Code, stricter supervision is being carried out on wastewater discharge monitoring. Regulators have raised higher standards for online water quality instruments used at wastewater outlets, including pH, dissolved oxygen and conductivity sensors. Factories in chemical, pharmaceutical, food & beverage industries, together with industrial wastewater treatment plants, are now entering a critical period to evaluate and upgrade their monitoring systems.

Core Updates in New Environmental Standards

Full data traceability to prevent distorted monitoring results Unique device identification codes are required for all field monitoring instruments during network access. Raw measurement data, calibration logs and equipment operation records must be stored for long-term review. Any modification to instrument parameters will be recorded automatically. Unauthorized devices cannot connect to official environmental monitoring platforms.
Higher standards for long-term measurement stability Wastewater usually contains sludge, weak acid, alkali and dissolved salts. Regulators demand sensors with reliable temperature compensation and low measurement drift. Sensors prone to corrosion, scaling and frequent deviation will be regarded as invalid monitoring equipment during official inspections.
Unified communication protocol for seamless data networking New standards standardize data interaction between sensors, transmitters and data collectors. Instruments shall support standard Modbus-RTU and stable 4–20mA analog signals. Outdated equipment with unstable signal output or incompatible communication cannot meet current compliance demands.

ACITEK Solutions for Regulatory Compliance
ACITEK offers a complete portfolio of water quality sensors and transmitters fully adapted to the latest environmental monitoring requirements: • AC580 series conductivity sensors, industrial pH electrodes and DO sensors feature built-in PT1000 temperature compensation. Wetted SS316L material provides anti-corrosion performance in complicated wastewater media. • G100 compact DIN rail transmitters support 4–20mA active output + RS485 Modbus dual signals. All parameter changes are logged automatically to meet traceability requirements. • Complete accessories including flow cells, immersion holders and mounting fittings comply with HJ installation & operation specifications.

Recommendations for End Users & System Integrators

For existing monitoring stations: Test sensor accuracy and signal stability in advance. Replace aging instruments in phases to avoid compliance risks.
For new wastewater treatment projects: Adopt integrated monitoring systems with both analog and digital communication to satisfy long-term regulatory demands.
Form standardized maintenance schedules, regularly clean and calibrate sensors and archive all calibration documents.

ACITEK provides professional technical support and customized online monitoring packages for wastewater discharge applications. If you need a complete solution for pH, DO and conductivity monitoring in wastewater projects, please contact our engineering team.

This paper presents three representative field application cases to verify the actual performance, economic benefits and technical advantages of ACITEK LDO Model 1 in seawater aquaculture, municipal wastewater treatment plant and coastal river nutrient monitoring projects.


Case 1: Seawater Industrial Mariculture Base Real-Time DO Control


1.1 Project Background


A large-scale coastal marine ranch in Fujian operates recirculating seawater breeding tanks for grouper and abalone, covering 12,000 m² breeding area.



Original monitoring scheme: Traditional polarographic dissolved oxygen electrodes
Pain points encountered:


Seawater contains high Cl⁻, algae and barnacle attachment; electrode membrane fouled within 7–10 days, data drifted severely;
Weekly membrane replacement, monthly electrolyte refilling, daily manual cleaning; 2 full-time maintenance staff required for 32 breeding tanks;
H₂S produced by residual bait decomposition poisoned polarographic electrodes, leading to invalid readings and delayed oxygen supply adjustment;
Without stable real-time DO data, aerators ran at full load all day, resulting in huge electricity waste; low DO at night caused occasional fish hypoxia mortality (annual loss over 180,000 RMB).






1.2 Solution Deployment


The project replaced all old electrodes with ACITEK LDO Model 1 seawater version dissolved oxygen sensors:



Installation: 1 probe per recirculation tank, installed on pipeline thread interface (standard thread compatible with existing tank fixtures); 10m matched sensor cable connected to ACITEK G800 controller;
Configuration: Factory pre-calibration, plug-and-play without on-site calibration; built-in automatic temperature compensation, immune to seawater temperature fluctuation 12–32°C;
Linkage control: Set DO threshold 5.0–7.5 mg/L; when DO <5.0 mg/L, system auto-starts aerators; when DO >7.5 mg/L, aerators reduce frequency or shut down.



1.3 On-Site Operation Results



Ultra-low maintenance workload

No consumables (membrane/electrolyte) needed. Only quarterly simple surface wiping of sensor cap required. The maintenance team cut staffing from 2 to 1 part-time worker, saving labor cost around 65,000 RMB annually. The sensor cap maintains 12-month service life covered by official warranty.
Strong seawater anti-interference performance

Not affected by high-concentration chloride, sulfide, residual feed organic matter and marine biofouling. Continuous 12-month immersion test showed no measurement drift, data accuracy kept ±0.05 ppm below 5 ppm as original specification.
Energy saving & mortality reduction

Precise aeration frequency regulation cut aeration power consumption by 22%. Night hypoxia incidents were completely eliminated; fish survival rate increased from 82% to 97%, reducing aquaculture economic loss by over 160,000 RMB each year.
Customer Feedback

"The ACITEK LDO sensor solves our long-standing seawater measurement trouble. Stable readings without frequent replacement parts greatly lower our operating cost, and scientific oxygen control significantly improved breeding output." — Farm Technical Director



Case 2: Municipal Wastewater Plant Secondary Biochemical Treatment Tank Monitoring


2.1 Project Background


A medium-sized municipal sewage treatment plant in Jiangsu adopts AAO secondary treatment process, daily treatment capacity 40,000 tons. Dissolved oxygen in aerobic tank is the core parameter to balance nitrification efficiency and aeration energy consumption.



Previous problem: Polarographic DO probes easily blocked by activated sludge foam; data fluctuated widely, unable to support automatic variable-frequency blower control; operators relied on manual sampling calibration twice per week, aerators operated with excessive air supply, high power consumption.



2.2 Project Scheme



Deploy 8 sets of ACITEK LDO Model 1 probes evenly distributed in aerobic biochemical tank;
Probe specification: 155mm length, 28.25mm diameter, Noryl corrosion-resistant body, maximum 3.5 bar pressure resistance adapting to tank immersion depth;
Data transmission: Max 100m transmission distance to G800 control unit, realizing real-time DO curve display and blower linkage regulation.









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Sensor Installed in Aeration Tank









2.3 Application Benefits



Stable measurement without flow demand

ACITEK LDO technology does not consume oxygen during detection, requiring no minimum water flow. Even in static sludge deposition zones, T90 response time <40s, quickly capturing DO concentration changes.
Cut down maintenance frequency drastically

Factory pre-calibration eliminates monthly air calibration work; no anode/cathode cleaning, membrane and electrolyte replacement. Calibration cycle extended to 6 months, annual maintenance time reduced by 70%.
Aeration energy consumption reduction

Stable continuous DO signal supports intelligent blower variable frequency control, maintaining aerobic tank DO steady at 2–3 mg/L. Annual power saving for aeration system reaches about 130,000 kWh, equivalent to 100,000 RMB electricity cost reduction.
Effluent standard compliance improvement

Stable dissolved oxygen environment promotes microbial nitrification, effluent ammonia nitrogen concentration stably below national discharge standard, compliance rate raised from 92% to 99.8%.



Case 3: Coastal Estuary Water Nutrient & Discharge Compliance Monitoring


3.1 Project Profile


Local ecological environmental bureau launched coastal river real-time water quality monitoring stations to track nutrient salt and DO variation, supervise industrial wastewater outlet discharge up to standard. Water body is brackish mixing fresh water and seawater, with complex interference substances including heavy metal ions, residual chlorine (<4 ppm), sulfate and surfactant.


3.2 Equipment Selection Reason


Traditional electrochemical DO sensors suffer severe cross-interference from H₂S, metal ions and chloride in brackish water, causing measurement distortion. ACITEK LDO Model 1 has exclusive anti-interference performance, unaffected by H₂S, K⁺, Na⁺, heavy metal ions, Cl⁻ and low-concentration residual chlorine, fully matching estuary water monitoring demands.


3.3 Field Operation Effect



Long-term continuous immersion for 10 months without data distortion, accurately recording daily DO fluctuation for nutrient eutrophication analysis;
Support remote unattended monitoring, sensor cable up to 10m, immersion depth up to 34m to cover multi-layer water body sampling;
One-point air calibration simple operation for routine inspection, convenient for environmental law enforcement personnel on-site verification;
Data provides reliable basis for early warning of algal bloom and pollution source tracing, assisting environmental management department to complete regular water quality assessment reports.



Core Advantages Verified by All Three Field Cases


Combining seawater breeding, municipal sewage and coastal environmental monitoring practical application data, ACITEK LDO Model 1 shows irreplaceable strengths compared with conventional DO electrodes:



Zero pre-use calibration & no drift

3D factory calibration before delivery, out-of-box usable; no signal drift under long-term continuous operation, ensuring long-period data authenticity.
Ultra-low operation & maintenance cost

No consumables (membrane, electrolyte), only annual replacement of sensor cap; labor and material maintenance expenditure reduced by over 60% versus polarographic sensors.
Powerful anti-interference for complex water bodies

Optical luminescent principle avoids electrode poisoning; suitable for seawater, sludge wastewater, brackish estuary water with various ion contaminants.
Wide environmental adaptability

0–50°C operating temperature, 3.5 bar pressure resistance, compact small footprint for flexible pipeline/tank installation; compatible with ACITEK G800 controller for automatic linkage control.
Cost-effective seawater dedicated version

Stainless steel sensing head with corrosion resistance against saline water, one-year full machine warranty, support OEM/ODM customized cable length and thread interfaces for engineering integrators.



Conclusion


ACITEK LDO Model 1 (AC9020000-SW) luminescent dissolved oxygen sensor has achieved remarkable energy-saving, labor-saving and efficiency-improving results in marine aquaculture, municipal wastewater secondary treatment and coastal water environmental monitoring projects. Its low-maintenance, high-stability and strong anti-interference characteristics perfectly solve the long-standing pain points of traditional dissolved oxygen electrodes in complex water quality scenarios, especially seawater working conditions. For water treatment system integrators, aquaculture enterprises and environmental monitoring institutions pursuing long-term reliable online DO detection, ACITEK LDO Model 1 is a preferred cost-performance optical dissolved oxygen monitoring solution.

ACITEK Team Explores WATERTECH CHINA 2026 for Industry Exchange


June 12, 2026

From June 9 to 11, WATERTECH CHINA 2026 (part of WieTec) was successfully held at National Exhibition and Convention Center (Hongqiao), Shanghai. As one of Asia’s top water treatment exhibitions, the event gathers thousands of global suppliers covering water quality monitoring, industrial wastewater treatment, smart water management and environmental restoration.


ACITEK’s technical and marketing team visited the exhibition to learn cutting-edge industry developments and conduct in-depth exchanges with peer manufacturers. The team focused on the latest technical solutions of dissolved oxygen sensors, conductivity probes and online analytical transmitters.


During communications with industry counterparts, we discussed hot topics including optical LDO technology optimization for seawater & wastewater applications, design improvements for low-maintenance water sensors, market demands from domestic projects and overseas markets, as well as challenges under complex working conditions. We shared practical field experience of our LDO Model 1 seawater dissolved oxygen sensor (AC9020000-SW) and CR-GS-10 two-electrode conductivity sensor.


This exhibition delivers valuable insights into market competition and technical trends. Moving forward, ACITEK will keep optimizing water quality sensing products for municipal wastewater, mariculture, pure water systems and coastal water monitoring. We look forward to further communication and cooperation with all partners in the environmental protection industry.