ATAGO CM-Isα Online Refractometer for Sulfuric Acid Concentration Monitoring

Overview

The ATAGO CM-Isα Online Refractometer is an intrinsically safe, process-integrated optical instrument engineered for continuous, real-time monitoring of sulfuric acid (H₂SO₄) concentration in industrial production environments. It operates on the fundamental principle of refractometry—measuring the refractive index (RI) of a liquid phase as a function of solute concentration—calibrated specifically for aqueous H₂SO₄ solutions across a broad operational range (0–80% w/w). Unlike offline titration or laboratory-based density measurement, the CM-Isα delivers second-by-second concentration data without sample extraction, chemical reagents, or operator intervention. Its robust sapphire prism sensor head is mounted directly into pressurized or recirculating process lines, enabling stable, drift-free operation under dynamic flow conditions. Designed for integration into distributed control systems (DCS) and programmable logic controllers (PLC), the instrument supports closed-loop feedback for automated acid dosing, dilution control, or crystallization endpoint detection—critical for sulfuric acid regeneration in metal pickling, fertilizer synthesis, battery electrolyte preparation, and spent acid recovery units.

Key Features

• Intrinsically safe certified sensor head (Ex ia IIB T3 Ga TA) compliant with ATEX Directive 2014/34/EU and IEC 60079-0/-11 for Zone 0/1 hazardous areas.
• High-precision sapphire prism optical interface with chemical resistance to concentrated H₂SO₄, hot acids, and aggressive cleaning agents (e.g., nitric acid passivation).
• Simultaneous real-time output of refractive index (RI), Brix-equivalent (% w/w), temperature, and user-defined concentration curves via factory or field calibration.
• Automatic temperature compensation (ATC) over 5–100 °C using integrated Pt100 RTD, eliminating manual correction and ensuring metrological traceability per ISO 21748 and ASTM D1218.
• Dual analog/digital output: isolated 4–20 mA current loop (HART-compatible) and RS-232C serial interface for SCADA integration and configuration via PC utility software.
• IP67-rated electronics housing with stainless steel (SUS316L) wetted parts, suitable for high-humidity, corrosive atmosphere, and washdown environments.

Sample Compatibility & Compliance

The CM-Isα is validated for direct in-line measurement of sulfuric acid solutions ranging from dilute (10 ppm. The instrument conforms to international standards governing safety-critical process instrumentation: IEC 61508 (SIL2 capable when integrated into safety instrumented systems), EN 61326-1 (EMC immunity), and ISO/IEC 17025 traceable calibration protocols. All factory calibrations are performed using NIST-traceable sucrose and sulfuric acid reference standards, with documentation supporting GLP/GMP audit requirements.

Software & Data Management

Configuration, calibration, and diagnostics are managed via ATAGO’s proprietary PC-based CM-Setup Utility (Windows OS), supporting multi-point linear/nonlinear curve fitting, alarm threshold definition (HI/LO, rate-of-change), and data logging at user-selectable intervals (1–60 s). The 4–20 mA output can be mapped to any primary variable (e.g., % H₂SO₄, RI, or temperature), and optional Modbus RTU firmware enables seamless integration into Rockwell Automation, Siemens PCS7, or Yokogawa CENTUM VP platforms. Audit trails—including calibration history, parameter changes, and fault logs—are timestamped and exportable in CSV format, satisfying FDA 21 CFR Part 11 requirements for electronic records and signatures when deployed in regulated manufacturing.

Applications

• Real-time concentration control in sulfuric acid alkylation units (petrochemical refining)
• Monitoring acid strength during copper/steel pickling line regeneration
• Electrolyte concentration verification in lead-acid battery manufacturing
• Process optimization in ammonium sulfate crystallization (fertilizer plants)
• Spent acid recovery via concentration staging in vacuum concentrators
• Quality assurance in pharmaceutical-grade acid synthesis (USP/EP grade)

FAQ

What is the maximum allowable process temperature for continuous operation?
The sensor head is rated for sustained exposure up to 160 °C; however, long-term stability above 100 °C requires optional high-temp gasketing and thermal shielding per ATAGO Technical Bulletin TB-CMIS-07.
Can the CM-Isα be calibrated for non-sulfuric acid solutions?
Yes—custom calibration curves for other binary mixtures (e.g., HNO₃/H₂O, NaOH/H₂O) can be programmed via the CM-Setup Utility, provided refractive index-concentration linearity is verified and documented per ISO 5725.
Does the instrument support digital communication protocols beyond RS-232?
Standard firmware includes RS-232 only; Modbus RTU and Profibus DP modules are available as factory-installed options (Cat. No. CM-Isα-MB / CM-Isα-PB).
How often does the prism require cleaning or maintenance?
Under typical clean-process conditions, no routine cleaning is required; fouling detection is enabled via real-time RI deviation alerts, and CIP-compatible flush ports allow automated solvent rinsing without disassembly.
Is validation documentation provided for GMP-regulated environments?
Yes—each unit ships with a Certificate of Conformance, Factory Calibration Report (NIST-traceable), and IQ/OQ protocol templates aligned with Annex 15 and ASTM E2500.