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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

Please click above to view this range

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 pH Measurment?

The pH of a solution measures the degree of acidity or alkalinity relative to the ionization of water sample. Pure water dissociates to yield 10-7 M of [H+] and [OH-] at 25 oC; thus, the pH of water is neutral i.e. 7: pHwater = - log [H+] = - log 10-7 = 7

Most pH readings range from 0 to 14. Solutions with a higher [H+] than water (pH less than 7) are acidic; solutions with a lower [H+] than water (pH greater than 7) are basic or alkaline. Measuring pH involves comparing the potential of solutions with unknown [H+] to a known reference potential. pH meters convert the voltage ratio between a reference half-cell and a sensing half-cell to pH values.

In acidic or alkaline solutions, the voltage on the outer membrane surface changes proportionally to changes in [H+]. The pH meter detects the change in potential and determines [H+] of the unknown by the Nernst equation: E = Eo + (2.3RT)/nF log {unknown [H+]/internal [H+]}

For more information on pH Measurement, please visit our technical area

How Can pH be Measured?

pH can be measured in the laboratory using a bench pH Meter, in outdoor and field applications a portable pH Meter would be used and for plant and process applications an online pH controller would be used.

A pH meter is a sophisticated volt meter capable of reading small millivolt changes from the pH electrode system. The meter is seldom the source of problems for pH measurements. Our pH meters have temperature compensation (either automatic or manual) to correct for variations in slope caused by changes in temperature. Microprocessor technology used in R.M.S instruments has created many new convenience features for pH measurement; auto-buffer recognition, calculated slope and % efficiency, log tables for concentration of ions and more.

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

Portable Hand Held Instruments:

Our EcoScan compact palm-top pH meters are economically priced, user-friendly and simple-to-use features such as : Microprocessor based, easy and quick push button calibration, auto buffer recognition, automatic temperature compensation (ATC), easy to read custom LCD, hold function, auto power off and self diagnostic.

Please Click on the picture below to view in detail:

Outdoor & Field Applications:


The very competitively priced R.M.S IP67 waterproof pocket-sized pH testers are the WORLD'S FIRST testers to utilize user-replaceable electrodes to enhance the useful lifespan of the instruments. These feather-weight testers are most ideal for rugged outdoor use and wet applications.

Please Click on the picture below to view in detail:

Waterproof Portable:

New Product!

When accuracy is as important as portability, The new CyberScan pH 600 Series is your perfect choice. Equipped with enhanced features such as higher resolution, ion measurement, a wide pH range and greater accuracy of up to 0.002pH, the meters are rugged and waterproof to IP67 standards, with GLP functions, wireless data transfer and a mega-memory that houses up to 500 data sets! In fact, we've made the pH 600 Series so powerful and versatile, it's like having a portable bench meter in your hands.

Please Click on the picture below to view in detail:

The CyberScan pH Meters are an ideal choice for anyone requiring to take pH 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.

Please Click on the picture below to view in detail:

Laboratory Applications:

Choose from our wide range of Bench pH meters, from the low cost, high specification CyberScan pH510 through to our top of the range touch-screen CyberScan pH5000. Incorporating advanced programmable features to suit the demands of today's scientist these meters make laboratory pH testing procedures routine with user-customisable options. Some top-of-the-line bench meters even automatically print or store measurements at timed intervals or when readings stabilise.

Please Click on the picture below to view in detail:

Plant & Process Applications:

Our Alpha 2000 is our top of the range industrial pH process control instrument. Advanced user-customizable features in the Alpha's powerful SETUP function include: Two Galvanically Isolated Scaleable 0-20/4-20 mA Outputs for fine control, 2 independent set-points with hysteresis protection, built-in proportional control, and noise grounding functions. Being menu-driven, the alpha range of controllers offer quick access and greater flexibility to configure measurement functions to suit the needs of process plants that demand high-end features at an economical price.

Please Click on the picture below to view in detail:

Replacement Sensors and Ancillaries:

At R.M.S Ltd we can supply replacement pH Electrodes for both Industrial and Laboratory applications 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 pH 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.

Please Click on the picture below to view in detail:

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We are proud to announce the pH600 series offering mega-memory capabilities: up to 500 data-sets, and gives you lab accuracy of up to 0.001 resolution. This versatile instrument is the ideal choice in today's demanding Laboratory and field environments with features such as, Wireless and cable-free data transfer with infrared IrDA technology. Comes with PC-based Complimentary Data Acquisition Software for hassle-free data import and report-generation into any popular spreadsheet programs of your choice. 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


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