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Endress + Hauser pH measurement selection guide
Engineering summary from PDF text extraction for Endress + Hauser pH measurement selection guide. Verify every value with the OEM datasheet.
Summary
Overview
This document is a selection and engineering guide for pH measurement in industrial processes, covering different industries and applications. It assists users in selecting the appropriate pH sensor and assembly, and includes information on transmitters.
pH Measurement Fundamentals
pH determination is a crucial measurement in all industries for monitoring product quality and chemical reactions. The pH value relates to the hydrogen ion (H⁺) concentration in an aqueous solution, indicating its acidity or alkalinity on a scale from 0 (acidic) to 14 (caustic). Application conditions can vary widely, from wastewater to ultra-pure water. The lifespan of a pH sensor is influenced by these conditions, as well as maintenance practices and the correct sensor selection. A complete pH measurement point includes the pH sensor, an assembly, cable, and transmitter.
Sensor Types
Glass Sensors
- Sensing Element: A thin salt layer on a glass bulb that incorporates H⁺ ions, causing a change in electrostatic potential. This potential is measured against a reference element via a junction.
- Variations: Available in hygienic and non-hygienic versions, differing in junction type (ceramic, Teflon, or none) and reference system (gel or liquid).
- Resistance: Junction and reference type selection impacts resistance to blocking and poisoning.
ISFET Sensors
- Sensing Element: An ion-selective field-effect transistor (ISFET) chip sensitive to H⁺ ions.
- Advantages: Unbreakable, can tolerate higher concentrations of organic solvents than glass sensors. Made from PEEK with lower alkaline and acid errors. Newer generations offer improved CIP stability.
- Applications: Preferred when glass is unsuitable, such as in food processes or with high organic solvent content (>20%).
Enamel Sensors
- Advantage: Robustness, long calibration cycles, extended lifetime, and reduced maintenance.
- Features: Liquid KCl filled reference with a hygienic ceramic junction. Operates in the pH range of 0 to 10. Suitable for CIP and SIP.
Combined pH/ORP Sensors
- Features: Include a platinum element for simultaneous pH and ORP (Oxidation-Reduction Potential) measurement. The platinum element can also be used to measure reference impedance for sensor quality monitoring. Directly provide rH values indicating the oxidizing or reducing nature of the medium.
Memosens Technology
- Principle: Inductive signal and energy transmission without metallic contacts, ensuring reliable operation in humid environments.
- Benefits:
- Stores calibration data in the sensor head for convenient lab calibration and quick on-site exchange.
- Memosens 2.0 offers enhanced data storage for predictive maintenance and improved IIoT connectivity.
pH Sensors and Application Limits
| Sensor Type | pH Range | Process Temperature | Max. Process Pressure | Min. Conductivity | Organic Content | Shaft Material | Junction | Reference System | Applications |
|---|---|---|---|---|---|---|---|---|---|
| Memosens CPS11E | 0 to 14 | 0 to 135 °C | up to 17 barabs | 50 µS/cm | < 20 vol% | glass | PTFE | gel filled | water, wastewater, process, chemical processes |
| Orbisint CPS11 | 0 to 14 | 0 to 135 °C | up to 14 barabs | 0.1 μS/cm | < 20 vol% | glass | ceramic | gel filled, ion trap | water, wastewater, process, chemical processes |
| Memosens CPS71E | 1 to 12 | 0 to 140 °C | up to 7 barabs | 10 µS/cm | < 20 vol% | glass | ceramic | gel filled, ion trap | hygienic and sterile applications (sterilizable, autoclavable) |
| Ceragel CPS71 | 1 to 14 | 0 to 140 °C | up to 7 barabs | 10 µS/cm | < 20 vol% | glass | ceramic | gel filled, ion trap | hygienic and sterile applications (sterilizable, autoclavable) |
| Memosens CPS61E | 1 to 12 | 0 to 110 °C | up to 7 barabs | 100 µS/cm | < 20 vol% | glass | ceramic | gel filled | hygienic and sterile applications (sterilizable, autoclavable) |
| Ceratex CPS31 | 1 to 14 | 0 to 80 °C | up to 4 barabs | 50 µS/cm | < 20 vol% | glass | ceramic | gel filled | hygienic and sterile applications (sterilizable, autoclavable) |
| Memosens CPS91E | 0 to 14 | 0 to 110 °C | up to 14 barabs | 500 µS/cm | < 20 vol% | glass | open | stabilized gel reference | emulsions, suspensions, precipitation reactions |
| Orbipore CPS91 | 0 to 14 | 0 to 110 °C | up to 14 barabs | 500 µS/cm | < 20 vol% | glass | open | stabilized gel reference | emulsions, suspensions, precipitation reactions |
| Memosens CPS41E | 0 to 14 | 0 to 135 °C | up to 11 barabs | 0.1 µS/cm | higher possible | glass | PTFE | liquid filled | process, ultrapure water, fat, dye |
| Ceraliquid CPS41 | 0 to 14 | 0 to 135 °C | up to 11 barabs | 0.1 µS/cm | higher possible | glass | PTFE | liquid filled | process, ultrapure water, fat, dye |
| Memosens CPF81E | 1 to 12 | 0 to 80 °C | up to 11 barabs | 100 µS/cm | < 20 vol% | glass | ceramic | gel filled, double chamber | wastewater, mining, drinking water, swimming pool water |
| Orbipac CPF81 | 1 to 14 | 0 to 110 °C | up to 11 barabs | 50 µS/cm | < 20 vol% | glass | ceramic | gel filled, double chamber | wastewater, mining, drinking water, swimming pool water |
| Memosens CPS31E | 0 to 14 | 0 to 110 °C | up to 7 barabs | 50 µS/cm | < 20 vol% | glass | ceramic | liquid filled | food and life sciences |
| Ceratex CPS31 | 0 to 14 | 0 to 110 °C | up to 7 barabs | 50 µS/cm | < 20 vol% | glass | ceramic | liquid filled | food and life sciences |
| Ceramax CPS341D | 0 to 10 | 0 to 140 °C | up to 7 barabs | 50 µS/cm | < 20 vol% | enamel | ceramic | liquid filled | food and life sciences |
| Memosens CPS77E | 0 to 14 | -15 to 135 °C | up to 11 barabs | 10 µS/cm | high level | PEEK | ceramic | gel filled | food, life sciences, fermenter, process, non aqueous media |
| Memosens CPS97E | 0 to 14 | -15 to 110 °C | up to 11 barabs | 500 µS/cm | high level | PEEK | open | stabilized gel reference | emulsions, suspensions, precipitation reactions, non aqueous media |
| Memosens CPS47E | 0 to 14 | -15 to 135 °C | up to 11 barabs | 5 µS/cm | high level | PEEK | ceramic | liquid filled | process, pure water, fat, dye, non aqueous media |
| Memosens CPS16E | 0 to 14 | 0 to 135 °C | up to 17 barabs | 50 µS/cm | < 20 vol% | glass | PTFE | gel filled, ion trap | water, wastewater, process |
| Memosens CPS76E | 0 to 14 | 0 to 140 °C | up to 14 barabs | 10 µS/cm | < 20 vol% | glass | ceramic | gel filled, ion trap | chemical process |
| Memosens CPS96E | 0 to 14 | 0 to 110 °C | up to 14 barabs | 500 µS/cm | < 20 vol% | glass | open | stabilized gel reference | emulsions, suspensions, precipitation reactions |
Assembly Types
Immersion Type Holders
- Applications: Open vessels and channels, such as in wastewater treatment plants or the chemical industry. Suitable for installations from the top of containers.
- Models:
- Dipfit (CPA111, CPA140): CPA111 (PP) for wastewater; CPA140 (PVDF/stainless steel) for harsher applications. Various immersion lengths, can hold up to three sensors. Spray cleaning options available.
- Modular Immersion Holders: Versatile for various sensor types and installation locations (pipes, rails).
- Flexdip (CYA112): For open vessels and channels. Modular system with stainless steel or PVC versions, assembly lengths from 600 mm to 3600 mm. Features a float assembly and quick fasteners.
Insertion Assemblies
- Applications: Primarily in batch processes where sensor access is between batches, common in life sciences and food production.
- Models:
- Unifit (CPA842): Stainless steel assembly for food and life sciences, with hygienic process connections (clamp, dairy fitting). EHEDG, 3-A, ASME BPE, and Pharma CoC certified options available.
Flow-Through Assemblies
- Applications: Installation in process pipes or bypasses, found in waterworks, beverage industry, chemical industry, and power plant analytical panels.
- Models:
- Flowfit (CPA250, CPA240, CYA21): CPA250 (PP) for waterworks; CPA240 (PVDF/stainless steel) for ultra-pure water. All offer multiple sensor slots and optional chemical spray cleaning. CYA21 is a compact option for limited space.
Retractable Assemblies
- Advantage: Allows sensor exchange or cleaning without process interruption. Manual or automatic (pneumatic) retraction is possible. Pneumatic versions can integrate with automatic cleaning and calibration systems.
- Models:
- Cleanfit: Offers various materials, sealing strategies, and safety functions. Ball valve sealing systems are available for heavy-duty applications. Pneumatic versions support the Liquiline Control system for automated processes.
pH Assemblies - Technical Data Summary
| Assembly Type | Model | Max. Process Pressure | Process Temperature | Materials (Medium Contact) | Sensor Connections | Process Connections | Cleaning | Remarks | Applications |
|---|---|---|---|---|---|---|---|---|---|
| Flow-through | CPA240 | SS: 11 bar @ 150°C; PVDF: 9 bar @ 50°C | SS: -15 to 150°C; PVDF: 0 to 120°C | PVDF, SS 1.4404/316L | 3 x PG 13.5 | Welding adapter DN 25, Flanges (DN 25 PN 16, ANSI 1” 150 lbs, JIS 10K 25A), FNPT ½” | Spray cleaning CPR31 | PMC, PWIS-free version | Water, boiler feedwater, ultrapure water, cooling water, fertilizer, petrochemical |
| CPA250 | 7 bar @ 20°C | 0 to 80°C | Polypropylene (PP) | 3 x PG 13.5 | G 1”, NPT 1” | Spray cleaning CPR31, Chemoclean CPR3 | Compact design | Water, wastewater treatment, beverages | |
| CYA21 | 17 bar | 0 to 100°C | SS 1.4404/316L | 1 x PG 13.5, NPT ½” | Pipe (6mm OD), common tube fittings | - | Ideal for limited space | Water, boiler feedwater, ultrapure water, cooling water | |
| Insertion | CPA842 | 17 bar | -15 to 140°C | SS 1.4435/316L | 1 x PG 13.5 | Hygienic clamp, Tri-Clamp, Dairy fitting, Varivent, Aseptic fitting | - | EHEDG, 3-A, ASME BPE, Pharma CoC options | Food, life sciences, chemical, water |
| Immersion | CPA111 | 5 bar @ 20°C | -10 to 80°C | Polypropylene (PP) | 3 x PG 13.5 | Flange DN 100, suspension bracket | Spray cleaning CPR30, CPR31 | Wet bucket | Water, wastewater, flocculant dosage, surface water |
| CPA140 | 11 bar (metal), 7 bar (PVDF) | PVDF: 0-120°C; SS: -15-150°C | PVDF, SS 1.4404/316L | 3 x PG 13.5 | Flange DN 80, ANSI 3”, JIS 10K 80A | Spray cleaning CPR30, CPR31 | Modular system | Chemical industry, petrochemical, power plants | |
| CYA112 | 1 bar | 0 to 60°C | PVC, SS 1.4404/316L | 1 x PG 13.5 or NPT ¾” | G ¾”, 1”; NPT ¾”; PG13.5 | - | Modular, float assembly available | Water/wastewater treatment, open channels, basins, fluctuating water levels | |
| Retractable | CPA871 | 17 bar (version dep.) | -10 to 140°C (version dep.) | SS 1.4404/316L, Alloy C22 | 1 x PG 13.5 | Clamp, Flanges, Thread NPT/G, Dairy fitting | - | Manual/pneumatic, immersion chamber version | Water, wastewater, process |
| CPA875 | 17 bar @ 140°C | -10 to 140°C | SS 1.4435/316L, Alloy C22 | 1 x PG 13.5 | Clamp, Aseptic, Neumo, Dairy fitting, Varivent | - | Manual/pneumatic, double chamber version | Food and life sciences processes | |
| CPA450 | 5 bar @ 130°C | -15 to 130°C | SS 1.4404/316L, Hastelloy C22, Titanium | 1 x PG 13.5 | Thread G/NPT, Flange ISO, ANSI | - | Manual, ball valve | Water, wastewater, process | |
| CPA451 | 3 bar @ 80°C | 0 to 80°C | SS 1.4404/316L | 1 x NPT ¾” | Thread G/NPT, Flange ANSI | - | Manual, ball valve | Water, wastewater | |
| CPA472D | 11 bar @ 100°C | 0 to 140°C | PEEK, PVDF, Alloy C22, Titanium, SS 1.4571 | 1 x PG 13.5 | Thread internal 1¼“, Flange DN50/80, ANSI 2”, JIS 10K 25A, Tri-Clamp, Dairy fitting | - | Manual/pneumatic, ball valve | Heavy-duty and process applications | |
| CPA473 | 7 bar @ 100°C | PA cylinder: max. 80°C; SS cylinder: 100°C | SS 1.4404/316L | 1 x PG 13.5 | Thread internal 1¼“, Flange DN50/80, ANSI 2”, Tri-Clamp, Dairy fitting | - | Manual/pneumatic, ball valve | Chemical industry, paper industry, sticky media | |
| CPA474 | 7 bar @ 80°C | PP: 0-60°C; PVDF/PEEK: 0-120°C | PP, PEEK, PVDF | 1 x PG 13.5 | Flange DIN/ANSI, Dairy fitting | - | Manual/pneumatic, ball valve | Paper industry, industrial water treatment |
Transmitters for pH Measurement
Liquiline CM42
- Features: Two-wire transmitter, intuitive operation with clear text menu (14 languages), suitable for Ex and Non-Ex applications. Compatible with Memosens sensors for predictive maintenance. Parameter changes (pH to conductivity, DO) are possible by sensor exchange.
- Outputs: 4 to 20 mA, HART, FOUNDATION Fieldbus, PROFIBUS PA.
Liquiline CM44 and CM44R
- Features: Digital four-wire transmitter, up to 8 channels, intuitive operation (17 languages). Supports 12 different parameters with Memosens sensors. Includes Heartbeat Technology for diagnostics and verification.
- Outputs: Up to 8 analog outputs (0/4 to 20 mA), up to 4 relays, HART, PROFIBUS DP, Modbus TCP/RTU, EtherNet/IP, Profinet. Remote access via Ethernet webserver. Available as field device or DIN-rail version.
Liquisys CPM223/CPM253
- Features: Panel-mounted (CPM223) or field housing (CPM253) versions. Optional relay functions for neutralization and spray cleaning.
- Outputs: 0/4 to 20 mA, HART, PROFIBUS PA/DP. Advanced diagnostic functions available.
Liquiline CM14
- Features: Basic transmitter for standard measuring points, fits common cabinet cut-outs. Easy commissioning with digital Memosens technology. Hot-plug capability for Memosens sensors allows quick replacement.
- Outputs: Up to 2 analog outputs (0/4 to 20 mA), 2 limit relays.
Liquiline Compact CM72/CM82
- Features: Smallest transmitters for Memosens sensors, attached directly to the sensor without independent power supply. Loop-powered two-wire devices. CM82 offers Bluetooth connectivity via the SmartBlue app for configuration and diagnostics. Suitable for hazardous and non-hazardous areas.
- Outputs: 1 analog 4 to 20 mA (CM72/CM82). CM82 features Bluetooth and HART.
Transmitter Technical Data Summary
| Transmitter | Measured Parameters | Input | Channels | Power Supply | Output | Display | Degree of Protection | Communication | Housing | Mounting | Specials |
|---|---|---|---|---|---|---|---|---|---|---|---|
| CM44/CM44R | pH, ORP, conductivity, O₂, NO₃⁻, NH₃, SAC, K⁺, Cl⁻... | Memosens, 4-20mA, digital | up to 8 | 24V DC/AC | up to 8 analog, max. 4 digital, 8 relays, fieldbus | Graphic, plain text | IP66/67 (field), IP20 (DIN-rail) | HART, PROFIBUS DP, Modbus TCP/RTU, Eth. IP, Profinet, Webserver | Plastic | Post, rail, DIN-rail, wall | 4-wire, multiparameter, Heartbeat Technology, math functions, cleaning/controller functions, modular, SD-Card |
| CM42 | pH, ORP, conductivity, O₂ | Memosens, analog | single | 100-230V AC; 12.5-30 V DC | up to 2 analog, fieldbus | Graphic, plain text | IP66/67 | HART, PROFIBUS PA, FOUNDATION Fieldbus | Plastic | Wall, post, panel | 2-wire, quick setup, navigator, sensor module replaceable, predictive maintenance, also suitable for analog sensors |
| CM14 | pH, ORP, conductivity, O₂ | Memosens | single | 24 V to 230 V AC/DC | up to 2 analog, 2 relays | 2 line LCD, dot matrix | IP65 (front), IP20 (housing) | - | Plastic | Panel | 4-wire, compact for cabinets, cost-efficient |
| CM72/CM82 | pH, ISFET, ORP, conductivity, O₂ | Memosens plug-in head | single | 12.6 to 30 V DC | 1 analog 4-20 mA | 2 line LCD | IP 67/68 | CM82: Bluetooth®, HART | PEEK | Space-saving | 2-wire, easy operation/commissioning, Bluetooth via SmartBlue App, direct sensor mounting |
| CPM253/CPM223 | pH, ISFET, ORP | Memosens, analog | single | 100/115/230 V AC, 24 V AC/DC | 2 analog, alarm relays, up to 4 additional relays | LED red/green | IP65 (field), IP30 (panel) | HART, PROFIBUS PA/DP | Plastic | Wall, post, panel | 4-wire, cleaning via timer/Chemoclean/PID controller, also suitable for analog sensors |
Check List / Data Sheet
A checklist is provided for complete specification, including customer contact data, medium properties (pH range, conductivity, chemical content), process data (temperature, pressure, flow), installation details, transmitter requirements, and necessary approvals/certificates (Ex, EHEDG, 3-A, FDA, SIL).
Selection of pH Sensor
The primary criteria for selecting a pH sensor are the chemical and physical characteristics of the process medium, aiming for maximum lifetime and minimal maintenance.
Application Categories:
- Standard Application: Conductivity > 50 µS/cm, Organic content < 20 vol %, No fibers/particles, No risk of poisoning (S²⁻, CN⁻, NH₃), Not hygienic or abrasive.
- High Organic Load: Organic content > 20 vol %.
- Low Conductivity: Conductivity < 50 µS/cm.
- Hygienic Applications: Food, Life sciences, Fermentation, WFI.
- Heavy-duty – Abrasive: High concentrations of abrasive particles.
- High Risk of Build-up: Pulp and paper, Process industry, Emulsions, Flue gas desulfurization.
- Chemically Demanding: Applications with aggressive chemicals.
Disclaimer
This extracted information may not include all figures, footnotes, or revisions. Contractual data must be confirmed against the official OEM PDF revision used for the specific project.
Official datasheet (PDF)
Curated from selected public technical reference material for discovery and preliminary comparison. This summary is not a substitute for a current certified manufacturer datasheet. Verify revisions and design limits before use.