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Instruments, Controllers & Sensors




Portable Turbidity meters

Bench Turbidity meters

Online Turbidity

Flame Photometry

BWB-1 Flame Photometer

Dissolved Oxygen (DO)

Handheld Dissolved Oxygen IP67 Dissolved Oxygen Meters

Bench Dissolved Oxygen Meters

Industrial Dissolved Oxygen 

Dissolved Oxygen Probes

DO Probe Conditioner


Portable pH Testers

Handheld pH Meters

Waterproof pH Meters

Bench pH Meters

Industrial pH Controllers

Replacement pH Electrodes


Free Chlorine

Total Chlorine

Cyanuric Acid

Redox (ORP)

Portable Redox Testers

Handheld Redox Meters

Waterproof ORP Meters

Bench ORP Meters

Industrial ORP Controllers

Replacement Metal ORP Probes

Conductivity (EC)

Portable Conductivity Testers

Handheld Conductivity Meters

Waterproof Conductivity Meters

Bench Conductivity Meters

Industrial Conductivity Meters

Replacement Conductivity Cells

Total Dissolved Solids (TDS)

Portable TDS Testers

Handheld TDS Meters

Waterproof TDS Meters

Bench TDS Meters

Industrial TDS Controllers

Replacement Cells

Ion Concentration

Handheld Ion Meters

Waterproof Ion Meters

Bench Ion Meters

Ion Selective Electrodes (ISE)


Portable Salinity Testers

Handheld Salinity Meters

Bench Salinity Meters

Salinity Sensors

Multi-parameter Bench Meters


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Multifunctional Controller


Chlorine Dioxide

Paracetic Acid

Hydrogen Peroxide 



Bench Resistivity Meters

Industrial Resistivity Controller

Resistivity Cells

Electrochemical Sensors

pH, Reference, Conductivity, Redox, Dissolved Oxygen, Ion Selective Electrodes, Calibration Solutions, Hollow Cathode Lamps and

Deuterium Lamps

What is Ion Concentration ?

Definition of Ion: ion - An atom or molecule that has a net electrical charge from gaining or losing electrons.

Chemical sensors are miniaturized analytical devices, which can deliver real-time and on-line information in the presence of specific compounds or ions in complex samples. Usually an analyte recognition process takes place followed by the conversion of chemical information into an electrical or optical signal. Among various classes of chemical sensors, ion-selective electrodes (ISE) are one of the most frequently used potentiometric sensors during laboratory analysis as well as in industry, process control, physiological measurements, and environmental monitoring. The principle of ion-selective electrodes operation is quite well investigated and understood.

An ion-selective membrane is the key component of all potentiometric ion sensors. It establishes the preference with which the sensor responds to the analyte in the presence of various interfering ions from the sample. If ions can penetrate the boundary between two phases, then an electrochemical equilibrium will be reached, in which different potentials in the two phases are formed. If only one type of an ion can be exchanged between the two phases, then the potential difference formed between the phases is governed only by the activities of this target ion in these phases. When the membrane separates two solutions of different ionic activities (a1 and a2) and provided the membrane is only permeable to this single type of ion, the potential difference (E) across the membrane is described by the Nernst equation:

E = RT/zF . ln (a2/a1)

If the activity of the target ion in phase 1 is kept constant, the unknown activity in phase 2 (a1 = ax) is related to (E) by:

E = RT/zxF . ln (ax/a1) = const + S . log (ax)

where S=59.16/z [mV] at 298 K and zx - the charge of the analyte. The potential difference can be measured between two identical reference electrodes placed in the two phases. In practice the potential difference i.e. the electromotive force is measured between an ion selective electrode and a reference electrode, placed in the sample solution. An examplary set-up for the measurement of electromotive force is precented in figure 1. It is important to note that this is a measurement at zero current i.e. underequilibrium conditions. Equilibrium means that the transfer of ions from the membrane into solution is equal to the transfer from the solution to the membrane. The measured signal is the sum of different potentials generated at all solid-solid, solid-liquid and liquid-liquid interfaces.

The above text was copied from pages from Warsaw University of Technology and was prepared by Wojciech Wroblewski (Copied from http://www.ch.pw.edu.pl/~dybko/csrg/tutorials/ise/index.html)

How Can Ion Concentration be Measured?

Ion Concentration can be measured in the laboratory using a bench Ion Meter, in outdoor and field applications a portable Ion Meter would be used.  

What products do R.M.S Ltd offer for Ion Measurement?

Portable Hand Held Instruments:

The R.M.S EcoScan Ion 6 portable Ion meter is ideal for water hardness testing, ions in feed or wastewater, sewage treatment, soil testing, fertilizer testing, plant tissue testing, food processing (sodium, potassium levels), geological testing. This competitively priced hand held Ion meter offers a user friendly, low-cost instrument ideal for measuring the Ionic strength of a wide range of applications. 

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Outdoor & Field Applications: 

The CyberScan 300 & 310 Meters are an ideal choice for anyone requiring to take Ion measurements in rugged outdoor field work or in situ Plant and Process applications - being waterproof and robustly built, the chance of accidental damage is virtually eliminated.  Not only is this instrument waterproof but in the event of accidentally dropping it into liquid, it will float to facilitate easy retrieval.

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Laboratory Applications: 

The high specification, economically priced Ion 510 Bench Ion Meter offering direct Ion concentration measurement with use of many Ion Selective Electrodes, is the idea choice for routine laboratory Ion measurements. With advanced features to suit the demands of today's scientist, sophisticated yet easy-to-use functions entail this microprocessor-based meter makes laboratory Ion testing procedures routine.

Please Click on the picture below to view in detail:







Replacement Sensors and Ancillaries:

At R.M.S Ltd we can supply replacement Ion Selective Electrodes that are compatible with all modern instruments. All of our electrochemical sensors can be supplied with or with out temperature compensation. All we need is the make and model of your Ion meter so that we can determine the correct connector etc - please email, phone or fax us with your requirements and one of our team will contact you. 

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We are proud to announce the launch of the Worlds First CFR 21 Compliant - Windows CE Driven Multi-Parameter 6000 Range of Bench Meters. Ideal for use in industries such as Pharmaceutical, Food & Drug Manufacture and Health & Human Services. Please click here for details.

We accept all major credit/debit cards - please contact us for our best possible prices!; any questions? Why not try our Technical Area where you will find an in-depth explanation of many relevant aspects within the field of electrochemistry! more..


Russell Mainstream Supply Ltd.


Cameron House, 8 Crown Square, Kingskettle, Cupar, Fife, KY15 7PW


Phone: +44 (0)1337 831192

Fax: +44 (0)1337 371192


Email: Sales@rmprocesscontrol.co.uk 



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