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What to consider when choosing liquid analysis instruments
Here’s how Fagerberg improves the everyday for the process industry.
Which properties of your liquid do you need to measure or monitor? The right analysis instrument depends on what you need to know about the medium, your process conditions and your measurement requirements.
Here, we guide you through the key factors to consider and provide an overview of different measurement parameters and their applications.
1. Start with what you need to measure
pH, conductivity, turbidity and dissolved oxygen provide information about different properties of a liquid. Other measurements, such as ORP and free chlorine, are used to monitor chemical processes and disinfection. The most relevant parameter depends on what you need to monitor or control.
2. Consider the properties of the medium
Clean water, wastewater and chemical process liquids place different demands on the sensor. Temperature, chemical composition, particles and deposits can affect both measurement results and sensor service life. Materials and measuring range must also be suitable for the medium.
3. Continuous measurement or sampling?
Do you need to monitor your process continuously, or is analysing individual samples sufficient? Continuous liquid analysis provides measurements directly from the process and can be used for monitoring and control. The measurement point and installation also affect how accurately the results represent the process.
4. Consider maintenance and calibration
Analysis sensors may need cleaning, inspection and calibration to provide reliable measurements. Requirements vary between measurement principles and depend on factors such as the medium and process conditions. Accessibility and the ability to remove the sensor for maintenance are also important considerations.
5. Adapt the installation to your process
Analysis instruments can be installed directly in pipes and tanks or in separate sensor assemblies and bypass measuring systems. Flow, pressure, temperature and available space all influence the installation. Demanding processes may require special assemblies and materials to protect the sensor and simplify maintenance.
6. Which type of liquid analysis is right for your application?
A brief overview of our different product categories.
Conductivity
Measures the electrical conductivity of a liquid and is used to monitor water quality, changes in concentration and cleaning processes. Available with both conductive and inductive measurement principles.
Dissolved oxygen (O₂)
Measures the amount of oxygen dissolved in a liquid. Used in water treatment, biological wastewater treatment and other processes where oxygen levels need to be monitored.
ORP (Redox)
Measures the oxidation-reduction potential of a liquid, also known as redox potential. Used to monitor redox conditions in applications such as water treatment and chemical processes.
pH
Measures how acidic or alkaline a liquid is. An important parameter for water treatment, neutralisation and process control in the chemical industry.
Suspended solids
Used to measure the concentration of suspended particles or monitor sludge levels in applications such as sedimentation tanks. Provides data for controlling and monitoring treatment processes.
Turbidity
Measures the cloudiness of a liquid using optical measurement. Used to monitor water quality, filtration and treatment processes.
Liquid analysis accessories
Sensor assemblies, transmitters and other accessories help adapt analysis instruments to the process. They can simplify installation, signal transmission and maintenance.
Free chlorine, chlorine dioxide (ClO₂) and ozone
Measure the concentration of disinfectants in water. Used to monitor and control disinfection processes in water treatment.
The most suitable measurement parameter and sensor depend on the medium, your process conditions and how the analysis results will be used.
Frequently asked questions
How often does a pH sensor need to be calibrated?
This depends on the medium, process conditions and accuracy requirements. Deposits, chemical exposure and ageing can change the sensor's properties over time. Calibration intervals should therefore be adapted to the application and reviewed regularly.
What is the difference between optical and amperometric dissolved oxygen measurement?
Optical oxygen sensors measure dissolved oxygen using oxygen-dependent optical properties of a sensing material. Amperometric sensors use an electrochemical reaction that generates an electrical current. Both can be used for continuous dissolved oxygen measurement, but differ in maintenance requirements and measurement conditions.
What is the difference between turbidity and suspended solids measurement?
Turbidity describes how cloudy a liquid is and is usually measured using light scattering. Suspended solids measurement determines the concentration of suspended material in the liquid and can be performed using optical sensors designed for higher particle concentrations. The two measurements provide different information and are not directly interchangeable.
How does temperature affect pH and conductivity measurement?
Temperature affects both the properties of the liquid and the sensor measurements. Temperature compensation can correct for certain temperature-dependent effects, but works differently for pH and conductivity. Temperature conditions and the properties of the medium must therefore be considered when selecting and calibrating instruments.
What is the difference between conductive and inductive conductivity measurement?
Conductive measurement uses electrodes in direct contact with the liquid and is suitable for applications such as low-conductivity water. Inductive measurement does not require electrodes in direct contact with the medium and is often a suitable option for higher conductivity levels, contaminated or aggressive liquids.
What is the difference between pH and ORP?
pH indicates how acidic or alkaline a liquid is, while ORP measures its oxidation-reduction potential. ORP is usually expressed in millivolts and is used to monitor redox conditions in water treatment and chemical processes. The two measurements provide different information and can complement each other.