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How Does An Oxygen Sensor Work?

Different industrial applications for quality control, process management, and environmental compliance all depend on oxygen sensors. Oxygen sensors measure the amounts of free oxygen in gases and liquids. Microorganisms are essential for degrading hazardous chemicals in liquid analytical applications, specifically wastewater treatment. These creatures typically need at least 5 ppm (parts per million) of dissolved oxygen to survive. For these processes to be healthy, it is essential to understand these levels. Analysing oxygen levels is crucial in many gas-based systems, especially those that employ nitrogen blanketing. Operators must make sure oxygen levels are kept to a minimum in these applications to prevent potentially disastrous reactions.

Temperature, water depth, salinity, bioactivity, and air pressure are just a few of the variables that affect oxygen levels. In order to effectively monitor oxygen in both gaseous and dissolved forms, it’s crucial to comprehend these variables. Let’s investigate how oxygen sensors function.

HOW OXYGEN SENSORS OPERATE

The two main types of oxygen sensor technologies are optical (luminescent) and electrochemical (Clark-Style/amperiometric). Both sensor types have characteristics that make them suitable for particular circumstances in different applications. We’ll look at how each type of sensor functions so you can decide which technology is most appropriate for your application.

ELECTROCHEMICAL SENSORS

Compared to luminous sensors, electrochemical sensors can read oxygen levels up to 45 ppm, a higher range. As a result, they are more suitable for demanding applications like chemical and water treatment.

The anode and cathode of these sensors are submerged in a reference electrolyte, and an oxygen-permeable membrane is linked to both of them. The anode and cathode must be polarised through a transmitter or similar power source in order to properly interpret the voltage. The cathode is often made of a precious metal that keeps the sensor’s polarisation stable. The oxygen crosses the membrane during in-process measurement. Anode and cathode register a voltage as a result of an electrochemical reaction that has finished in the electrolyte.

The generated current will increase as the oxygen levels rise. The voltage will subsequently be translated into a legible oxygen value via a transmitter.

OPTICAL SENSORS

On the market, optical oxygen sensors are a relatively recent sensor type. These sensors are now being used more frequently in a variety of industrial processes thanks to technological advancements in this field.

They work using an inside LED light and an external cap that has a fluorescent dye layer that is oxygen-sensitive. Additionally, a coordinated internal receiver converts light waves into readable oxygen levels. The wavelengths produced between the light and the dye layer will travel quickly to the transmitter in the absence of oxygen. The waves will move much more slowly after oxygen comes into contact with the dye layer.

MAINTENANCE IS KEY TO KEEPING SENSORS FUNCTIONAL & ACCURATE

The model of the sensor determines the specific maintenance procedures needed to increase sensor lifespan and guarantee correct measurements.

Electrochemical Maintenance: A little more upkeep is needed for electrochemical sensors than for luminescent ones. Users must polarise the reference system using a transmitter or similar power source, as was already described. The reference system may need to be stabilised for several hours. Regular cleaning of the anode and cathode is also necessary to prevent wear, especially on the precious metal cathode. If the reference system is not correctly maintained, readings will start to drift and measurements will be inaccurate.
Optical Maintenance: The condition of the exterior cap housing the dye layer is crucial for sustaining a luminous oxygen sensor. Long-term exposure to corrosive or other abrasive environments will cause the luminous dye layer to degrade. The wavelength patterns of the LED light will alter due to a broken dye layer, which will reduce measurement accuracy. However, damaged dye layer caps can simply be replaced without needing a new sensor altogether.

DISCOVER WHICH MODEL WORKS FOR YOU

Both types of oxygen sensors offer advantages that allow them to be used in a variety of applications that call for oxygen measurements. Examine our choices for oxygen sensors to see which one suits your process the best.

Essential Industrial Wastewater Treatment Equipment

ALAR Water Treatment and M4 Knick team up to ensure regulatory compliance in wastewater treatment

Maintaining clean waterways is crucial to conducting business. Responsible water management practises are the first step in complying with wastewater discharge rules. A thorough awareness of industry practises, the characteristics of water pollution, chemical treatment techniques, and the technology employed to meet environmental and financial needs is necessary for implementing an environmental stewardship programme.

Quality Wastewater Treatment Equipment

Equipment to prevent water pollution is designed and built by ALAR Water Treatment LLC, an Ovivo Company, for the manufacturing and commercial production sectors. For production and manufacturing businesses in need of practical, affordable industrial wastewater equipment solutions, ALAR Water Treatment provides the greatest technology currently accessible. TSS, FOG, Heavy Metals, Insoluble BOD, and pH environmental discharge and disposal compliance are met by these custom-built systems.

Due to ALAR’s diversification into other industries, reliable pH and ORP monitoring tools are now required. The demand for sensors that can endure harsh chemical and wastewater environments is strongest in manufacturing and production facilities. In addition to durability, the majority of design requirements call for autonomous self-cleaning systems that can operate dependably in remote areas. Therefore, the concrete, food and beverage, flexographic ink, metal finishing, oilfield, and paint and coatings industries make the most requests for these system changes.

Conductivity, oxygen, and pH/ORP measurements are the main areas of focus for M4 Knick in the industrial and municipal markets. Sensors, analyzers/transmitters, portable metres, fittings, and automated wastewater treatment systems are among the M4 Knick product line’s offerings.

The Memosens® digital technology from Knick lies at the core of the M4 Knick solution package. Memosens is a digital connection and communication protocol that enhances measurement accuracy, cuts down on time spent doing in-field maintenance, and raises user safety standards in general.

A Partnership Benefiting the End-User

In order to use them with their Micro-KleanTM, Auto-Vac®, and Flex-O-Star® chemical delivery and sludge dewatering systems, ALAR has been using M4 Knick Sensogate and CSR 225 Retractable Holders, SE 555 pH sensors, MemoRail Modbus transmitters, and Portavo portable metres since 2017. The end-user will profit from all of the above:

• All system information is available on one HMI screen
• Automatic Sensor Cleaning
• Automatic Chemical Addition
• Highly accurate pH Adjustment
• More accurate sensor measurements using an offline calibration process
• Eliminates the influence of moisture ingress from submersion or humid environments
• Digital PLC Datalog Capabilities
• Predictive maintenance – the system continuously monitors: pH sensor wear, glass impedance, zero-point, pH slope, response time, calibration intervals.

  In conclusion, ALAR Water Treatment and M4 Knick will help you satisfy your regulatory compliance needs for wastewater treatment, and we’ll do it with a system that requires little upkeep, is secure, and is simple to operate.

Multi-parameter Liquid Analyzer Delivers Ultimate Flexibility

The Stratos Multi analyzer from Knick offers the utmost flexibility in terms of pH/ORP, conductivity, and oxygen measurement for both plant operations and maintenance. The compatibility and functionality of PLC/DCS and process installations are increased by providing a variety of alternatives for power, sensor inputs, and signal outputs. In other words, the days of keeping a variety of transmitters in stock to support the installed base of measurements in your plant are over; now, there is only need for a single transmitter for almost all applications.

Perfect Flexibility in the Process Unit 

Installing or retrofitting a universal 4-wire power supply (24…230 V AC/DC) is possible in almost any space.

Measurement of up to two (2) pH, ORP, conductivity, or dissolved oxygen applications in any combination is possible thanks to multi-parameter capabilities.

Practically any Analogue, Memosens Digital, or ISM Digital sensor is compatible with the open platform idea.

Stretch your Control System

The Stratos Multi offers a variety of choices for acquiring process data and sensor diagnostics, which can improve your control system. As an illustration, the Stratos Multi provides:

• Up to (4) 4…20mA outputs
• (3) relays configurable for alarm, limit, PID control, or wash
• HART
• Ethernet/IP

Added Flexibility with Memosens

It will also take less time to calibrate and maintain sensors when Stratos Multi and Knick Memosens sensor technology are combined.

Smart digital sensors offer diagnostic information that enables quick performance evaluation and necessary maintenance. The multi-color screen on the Stratos Multi provides sharp, simple graphics.

You no longer need to spend a lot of time inside the process unit to complete offline calibration; instead, you can use a Portavo portable metre or the MemoSuite programme. Simply connect a pre-calibrated sensor to Stratos Multi to resume taking measurements. It now just takes a few minutes to complete a task that used to take 30 to 45 minutes. Offline calibration thus lowers maintenance expenses while raising worker safety in the facility.

Both plant maintenance and operating requirements can be balanced by a single transmitter. The multi-parameter Stratos Multi can help your process operate at its best.

How Does A Ph Sensor Work in industry ?

The litmus paper tests from elementary school are often what come to mind when most people think about pH measuring. The pH chart will show how acidic or basic the solution is based on how the litmus changes colour after being dipped in the solution.
Numerous industrial processes necessitate pH analysis for various reasons. They involve analysing chemical reactions, ensuring product safety, and maintaining product quality. These processes frequently take place in challenging circumstances and call for far more sophisticated apparatus, which is significantly more advanced than the old experiments we did in primary school. The pH sensor is the most crucial piece of equipment here. So let’s investigate how a pH sensor functions.

pH SENSOR OPERATION

Electrodes are used by pH sensors to track hydrogen ion activity in a solution. In doing so, the measuring electrode compares the measured voltage from the internal reference electrode to the ion exchange through the gel layer created on the glass membrane.

UNDERSTANDING THE COMPONENTS OF A pH SENSOR 

The components of the pH sensor need also be understood in order for us to fully comprehend how a pH sensor operates. Diagram

Glass membranes and specialised glass bodies used in industrial pH sensors are made according to a unique recipe that is compatible with the process liquids. Three electrodes—a measuring electrode, a temperature electrode, and a reference electrode—are present in the glass body. A crucial element of the reference system, which also comprises electrolyte, is the reference electrode. The electrolyte is intended to maintain neutrality at pH 7.

When the immersed sensor makes contact with the liquid, a sensitive gel layer is created in the specific pH glass. The measurement electrode produces a voltage in response to the hydrogen ion activity near the gel layer. Additionally, the solution being measured and the internal reference electrode need to be electrically connected. A liquid junction is used for this. Depending on the type of sensor, junctions can be ceramic, open-hole, or PTFE. To determine the recorded pH value, the potentials from each of these electrodes are crucial. You receive a pH reading from the transmitter or the head of a clever digital sensor after doing the computation.

If you don’t take good care of these parts, your pH sensor’s accuracy will degrade and the potentials could not be trustworthy.

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SENSOR MAINTENANCE IS THE KEY TO KEEPING YOUR SENSOR FUNCTIONAL AND ACCURATE 

Like any tool, sensors occasionally need upkeep to keep working effectively. A few situations that can affect a sensor’s longevity include increased temperatures and solution accumulation, particularly from alkaline solutions.

Sensors come in a variety of sizes and shapes, each one designed for a particular application. To choose the sensor that works best for your process, check out our catalogue.

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2-point And 3-point Calibration Comparison For Ph Measurements

To guarantee that your pH sensor is operating properly and giving reliable readings, a number of crucial elements must be in place. Understanding the calibration procedure and how it affects your pH measurement range is the first step in achieving accurate measurements. You anticipate a process to function in accordance with the accepted calibration procedures when calibrating sensors by setting two points on the pH scale. The industry standard for calibrating pH sensors is the 2-point calibration technique. Although single-point and three-point calibrations are less common, each technique has a place in pH measurement. The following will be looked at in this article:
1)  Calibration’s contribution to measurement accuracy
2)  2-point and 3-point calibration characteristics
3)  When to use each calibration technique

Calibration Basics 

For precise measurements, calibrating your sensor is essential. Calibrations can be carried out in a variety of methods by you, your operators, and your professionals. Some ways may be more effective than others depending on the configuration and the process involved.
Understanding a pH sensor’s slope and zero-point is crucial before beginning the calibration process. Each sensor’s values are particular to that sensor. The sensor’s slope is the linear relationship between the pH value and raw voltage (mV) readout. This indicates that in a perfect world, the mV value at pH 7 is zero. Then, as the value changes from pH 7, it should rise or fall by 59.16 mV/per unit of pH.
Unfortunately, there is no perfect world because every sensor is different. Each sensor is calibrated to the slope and zero-point in relation to the theoretical values so that it can account for variations brought on by ageing and process exposure.

Using 2-Point Calibration

The most common and advised calibration technique is 2-point calibration. Many people believe that the more calibration buffers used in a pH measurement application, the more accurate the result will be. This is only occasionally true. Users have discovered that regulated 2-point calibrations may deliver extremely accurate and dependable readings in the majority of applications as industry technology has advanced. The sensor can precisely read the pH of a solution by adjusting your electrode with two particular buffers on the pH scale. We frequently advise performing two-point calibrations using pH buffers 4 and 7, then performing a third-point validation.

Adding a third point to your 2-point calibration allows people used to 3- or multi-point calibration to have further confidence in the sensor’s accuracy. When doing routine maintenance or addressing a particular performance issue, a technician can use a Portavo portable metre that has undergone 3-point calibration in the field. They now have a third source of data to compare to the process reading and lab measurement after obtaining a sample of the process and measuring and data logging with the Portavo. The process measurement may now be quickly and accurately validated without the permanent addition of a third, possibly superfluous variable.

Using 3-Point Calibration

When attempting to cover an even greater pH range, we can use 3-point calibration. As was previously stated, going beyond the two buffer points does not guarantee that a reading would be more accurate. Once more, the majority of 2-point calibrations use the pH 4 and pH 7 suggested buffers.

Users frequently need to set buffers higher on the pH scale for 3-point calibration. Historically, deterioration has been more likely to occur with higher buffers in alkaline ranges. This is especially true when the sensors are subjected to the challenging conditions they work in. This exposure can eventually result in faulty readings and a misalignment of data over time. Such pH data interruption could have a negative impact on costs, time, and output in many of these contexts, including the food and beverage, pharmaceutical, and CIP (clean-in-place) industries, as well as the fertiliser manufacturing process. A 3-point calibration may be required in some applications, particularly those involving processes where values are commonly found to exceed pH 10, in order to cover that wider range.

2-point and 3-point Calibration Summary

Keep in mind that every sensor calibration is specific to the process you are studying. Both the 2-point and 3-point calibration procedures have advantages. But the key to ensuring accuracy is knowing which is preferable for your application. Which method best fits your analysis depends on whether your buffers are applicable to this procedure. For additional details on calibrations and buffers, see our informative films and practical instructions.

True Asset Management Of Your Ph, ORP, Conductivity, & Oxygen Sensors

A Data-Driven Paradigm Shift for Asset Management

How many pH probes are there in your plant, exactly? Although it would be simple to respond to that question, do you know how well each performs and how long it will last? Keeping an eye on your assets is always a top responsibility when running an industrial process facility. Critical assets frequently include liquid analytical sensors. These sensors are essential to the smooth operation of processes, the maintenance of constant quality, the prevention of equipment corrosion, and regulatory compliance.
Employees at plants frequently view liquid analytical sensors as disposable. However, if you can guarantee that your sensors are performing at their peak levels and living longer than average, you’ll save a tonne of money. Why can’t you do this? With the help of historical data and asset management, it is feasible. You can receive a macro and micro perspective of what is occurring with your sensors and, in certain situations, your process using digital pH, ORP, conductivity, and oxygen sensors and data gathering software designed for liquid analytics.

The Possibilities of Asset Management for Liquid Analytics

Smart digital sensors that utilise interference-free signals are what Memosens Knick sensors, for example, offer their customers. Memosens sensors have internal memory that stores previous data. This information includes everything from the sensor’s identification (such as its model, serial number, associated tags, and name of assigned application) to the events it has gone through (such as its most recent calibration, the amount of wear and life it has left, the number of CIP cycles, and the amount of time it spent in extreme measurement ranges).
You can instantly get data from a smart digital Memosens sensor for collection and sensor management when you combine it with software like MemoSuite Advanced. Even offline calibrations are possible. Users acquire a thorough grasp of sensor performance for each application by compiling historical data from analytical sensors used in plants. Techs can utilise this data to develop predictive maintenance plans and pinpoint the precise repair each application needs.

Maintaining Assets within Certified Guidelines

For pH sensors, regular, frequently approved calibration procedures are crucial. A secure GMP and FDA CFR 21 Part 11 compliant database is provided for calibrations carried out utilising a data collecting and asset management tool like MemoSuite Advanced. With MemoSuite, users are able to calibrate up to 10 sensors at once using user-defined calibration techniques like GMP (Good Manufacturing Practise) or Knick’s “Calimatic” automatic calibration. For accurate calibrations and subsequently improved accuracy, the Calimatic function makes use of automatic buffer recognition and temperature adjustment. After the sensor has been calibrated and adjusted, the record is safely stored in the software’s database. Additionally, users can design their own calibration certificate templates. Regulatory compliance is ensured by unchangeable digital data.

Summary

The ideal strategy to handle and comprehend your liquid analysis sensors is to use digital technology along with asset/data management software. The question “Are you getting the most life and best performance from your sensors?” can be answered with straightforward software like Memosens Advanced. You will also discover that you have all you require to create a data-driven strategy to improve your process.