Browse Analytical Instruments
Liquid analysis
Liquid analysers measure the chemical and physical properties of water and process liquids. They’re used across water and wastewater treatment, food and beverage, dairy, chemical processing and environmental monitoring.
pH sensors
Suitable for: Liquids
pH sensors measure the hydrogen-ion activity of water-based solutions, showing how acidic or alkaline they are on a scale of 0 to 14. They’re widely used in water treatment, chemical, food and process applications, and pH can also be used to infer chemical concentration. A typical sensor pairs a glass measuring electrode with a reference electrode, and temperature compensation keeps readings accurate as process conditions change.
Conductivity analysers
Suitable for: Liquids
Conductivity analysers measure a liquid’s ability to carry an electrical current, reported as conductivity or resistivity. They suit both simple and complex processes, from high-purity water to acids and caustic cleaning solutions. Using a concentration curve or table, the analyser can calculate concentration from the known properties of the liquid.
Contacting sensors use electrodes immersed in the liquid. Where fouling or corrosion is a problem, toroidal (inductive) sensors measure without exposed electrodes, using two closely coupled coils immersed in the solution.
Ion-selective electrodes (ISE)
Suitable for: Liquids
Ion-selective electrodes measure the activity of one specific ion dissolved in a solution and convert it into an electrical potential. Based on the known properties of the liquid, this gives you the concentration of ions such as ammonium, nitrate, chloride, fluoride and sulfide, as well as some metals. ISEs are commonly used for nutrient monitoring in wastewater treatment and for environmental water quality.
Oxidation reduction potential (ORP)
Suitable for: Liquids
Oxidation reduction potential (ORP), also known as redox, measures a solution’s ability to oxidise or reduce another substance, expressed in millivolts. It’s a cost-effective way to monitor processes that contain oxidisers or reducers such as chlorine, ozone and bromine. ORP is often used to confirm disinfection performance in water treatment and to control chemical treatment of industrial wastewater. It shows how active the oxidiser or reducer is, rather than its exact concentration.
Dissolved oxygen (DO)
Suitable for: Liquids
Dissolved oxygen (DO) is the amount of oxygen dissolved in water, usually expressed in mg/L or percent saturation. It’s a key measurement in wastewater aeration, aquaculture and environmental water quality monitoring.
Two technologies are used: electrochemical (membrane) sensors and optical (luminescent) sensors. Optical sensors generally need less maintenance and don’t consume oxygen, while electrochemical sensors remain a proven, economical choice for many applications. In aeration control, accurate DO measurement can also help reduce blower energy use.
Turbidity and suspended solids
Suitable for: Liquids (including slurries)
Turbidity and suspended solids sensors use optical methods to measure the cloudiness of water caused by suspended particles. The sensor measures how light is scattered or absorbed and converts this into turbidity units, such as nephelometric turbidity units (NTU) or formazin nephelometric units (FNU), or into total suspended solids (TSS) in mg/L or ppm. These measurements are widely used in drinking water, wastewater, industrial and environmental applications.
Where solids content is very high or particle size varies widely, microwave or ultrasonic sensors can give a more reliable result than optical devices.
Gas analysis
Gas analysers measure the concentration of specific gases in combustion, emissions, process, biogas and gas purity applications, including oxygen, one of the most commonly measured gases of all. Alongside the general-purpose technologies below, zirconia and paramagnetic analysers are designed specifically for oxygen. The right technology depends on the target gas, its concentration range and the other gases in the sample.
Nondispersive infrared (NDIR) gas analysers
Suitable for: Gases
Nondispersive infrared (NDIR) analysers suit a wide range of gas measurements, including carbon dioxide, carbon monoxide and methane, each of which absorbs infrared light at known wavelengths. “Nondispersive” means the analyser doesn’t split the light into a spectrum with a prism or grating; instead, an optical filter passes only the wavelength of interest.
Sample gas flows through a measuring cell with an infrared source at one end and a detector at the other. The amount of light absorbed is proportional to the gas concentration and is converted into a measurement signal. A reference measurement, from a second cell filled with a non-absorbing gas or at a wavelength the gas doesn’t absorb, corrects for drift caused by temperature changes and component ageing.
Analysers with multiple filters or a rotating filter wheel can measure more than one gas at the same time. A related method, photoacoustic detection, measures the tiny pressure pulses produced as the gas absorbs infrared energy and warms, which are also proportional to concentration.
Ultraviolet (UV) gas analysers
Suitable for: Gases
Ultraviolet (UV) analysers work on a similar principle to NDIR analysers, but use ultraviolet light. They’re the better choice when the target gas doesn’t absorb enough infrared light, and they suit low concentrations and samples where water vapour would interfere with an infrared measurement. Typical measurements include sulfur dioxide, nitric oxide, nitrogen dioxide and hydrogen sulfide.
For some gases, a UV fluorescence method is used instead: the analyser measures the light the gas emits after absorbing UV energy.
Thermal conductivity (TC) analysers
Suitable for: Gases
Thermal conductivity (TC) analysers suit binary gas mixtures, where the target gas conducts heat noticeably differently from the background gas. The sample passes over a heated element, and the heat it carries away changes the element’s resistance, which is converted into a concentration reading. A second cell containing a fixed reference gas compensates for ambient changes, improving accuracy and reducing drift.
TC analysers are best suited to measuring hydrogen and helium at percentage levels, and can also measure gases such as argon and carbon dioxide, depending on the background gas. A common application is monitoring hydrogen purity in hydrogen-cooled generators.
Electrochemical gas analysers
Suitable for: Gases
Electrochemical analysers are a cost-effective and sometimes essential solution for gas concentrations from very low (ppm) to high percentage levels. A typical sensor has a gas-permeable membrane covering an electrolyte and several electrodes. As the target gas passes through the membrane, it reacts chemically and produces a small current that is proportional to its concentration.
Electrochemical sensors are consumable and are replaced periodically, much like a battery. Sensor life depends on sample flow, gas concentration, moisture and any background gases that could poison the sensor. With careful selection, sensors typically last from several months to several years.
Common applications include portable and fixed combustion analysis, area monitoring, process measurement and blanket gas analysis. For monitoring toxic and combustible gases to protect people, see our Gas Detection range.
Zirconia oxygen analysers
Suitable for: Gases
Zirconia oxygen sensors use a zirconium oxide (zirconia) ceramic cell with porous electrodes on each side. One side is exposed to reference air and the other to the process gas. Because the two sides have different oxygen levels, the cell produces a voltage (described by the Nernst equation) that is converted into an oxygen concentration.
Zirconia only conducts oxygen ions at high temperatures, so the cell is heated electrically or by the process itself, for example when installed directly in a flue or furnace. Zirconia sensors are rugged, respond quickly and measure from ppm to percentage levels, making them the standard choice for combustion control on boilers and furnaces. They aren’t suitable where the sample contains high levels of combustible gases, as these react on the hot cell and cause low readings.
Paramagnetic oxygen analysers
Suitable for: Gases
Paramagnetic analysers use a property that sets oxygen apart from most other gases: it is strongly attracted to a magnetic field. In the common dumbbell design, the sample passes through a strong magnetic field around a small glass dumbbell on a fine suspension. Oxygen in the sample pushes on the dumbbell with a force proportional to its concentration, and this is measured electronically.
Paramagnetic analysers are accurate across the full 0–100% range, respond quickly and have no consumable sensor. With a clean, dry sample and regular maintenance, they give long, reliable service in process, laboratory and gas purity applications.
Solids analysis
Solids analysers measure the moisture and other constituents, such as oil, fat and protein, of bulk and manufactured products. This once meant taking samples to a laboratory. Today’s analysers measure directly on the production line, giving you continuous data for process control, quality and compliance, even in harsh factory environments.
Near infrared (NIR) moisture and constituent analysers
Suitable for: Solids
Near infrared (NIR) analysers work on the same principle as many gas and liquid analysers: constituents absorb light at specific wavelengths. In the near infrared range, this gives high sensitivity to moisture, oil, fat, protein, resins and coatings.
The analyser directs light through a rotating wheel of narrow-band filters onto the product. Measurement filters target the constituent of interest, while reference filters compensate for changes in the product’s colour and texture. Light reflected from the product returns to a detector and is converted into a concentration reading.
Installation is non-contact: the analyser mounts above a conveyor or web, or views product in pipework or chutes through a window or sample port. Typical products include snack foods, minerals and wood chips. Because NIR light only penetrates the surface, it’s best suited to products where the surface is representative of the whole, such as powders, wood fibre and chips.
Radio frequency (RF) moisture analysers
Suitable for: Solids
Radio frequency (RF) moisture analysers use a dielectric measurement to determine the moisture content of a product. Because RF energy penetrates deep into the material, the reading reflects total moisture rather than just surface moisture, which matters when moisture isn’t evenly distributed. This makes RF analysers well suited to plasterboard, wood panels and food products such as wheat.
The sensor acts as an antenna and is available in configurations for high-temperature, solid, granular and viscous products, including bakery dough and honey.
Choosing the right analyser
There are many ways to make these measurements, so we focus on recommending reliable, technically advanced instruments that reduce complexity for your business. When recommending an analyser, we consider:
- the properties of the liquid, gas or solid being measured
- the process connection and mounting location
- the pressure and temperature of the process and its surroundings
- your preferred units of measurement and output signal
- power, installation and maintenance requirements
- hazardous area, compliance and certification requirements.
Which technology suits your measurement?
| What you need to measure | State | Technology |
|---|---|---|
| Acidity or alkalinity | Liquids | pH sensors |
| Dissolved salts or chemical concentration | Liquids | Conductivity analysers |
| Specific ions, such as ammonium or nitrate | Liquids | Ion-selective electrodes |
| Disinfectant or oxidiser activity | Liquids | ORP |
| Oxygen dissolved in water | Liquids | Dissolved oxygen sensors |
| Cloudiness or suspended solids | Liquids | Turbidity and suspended solids sensors |
| Carbon dioxide, carbon monoxide or methane | Gases | NDIR analysers |
| Low levels of sulfur dioxide, nitrogen oxides or hydrogen sulfide | Gases | UV analysers |
| Hydrogen or helium in a binary mixture | Gases | Thermal conductivity analysers |
| Combustion gases with a portable analyser | Gases | Electrochemical analysers |
| Oxygen in a flue or furnace | Gases | Zirconia oxygen analysers |
| Oxygen purity from 0 to 100% | Gases | Paramagnetic oxygen analysers |
| Surface moisture, fat or protein on a conveyor | Solids | NIR analysers |
| Total moisture in board, grain or dough | Solids | RF moisture analysers |
As well as supplying the right instrument, we can maintain and repair it for you. See our Calibration & Service page for more.
Frequently asked questions
Which analyser should I use to measure oxygen in a boiler flue?
A zirconia oxygen analyser is the usual choice. It can be installed directly in the flue, responds quickly and measures accurately at the high temperatures found in combustion processes.
What’s the difference between optical and electrochemical dissolved oxygen sensors?
Optical (luminescent) sensors generally need less maintenance and don’t consume oxygen during measurement. Electrochemical (membrane) sensors are a proven, economical option for many applications.
How often do electrochemical gas sensors need replacing?
It depends on the application. With careful selection, sensors typically last from several months to several years, depending on sample flow, gas concentration, moisture and background gases.
Can moisture be measured without touching the product?
Yes. Near infrared (NIR) analysers mount above a conveyor and measure moisture and other constituents without contact. Radio frequency (RF) analysers are used where total moisture, not just surface moisture, needs to be measured.