FJA-04 Online pH Transmitter with Integrated Display

Overview

The FJA-04 Online pH Transmitter is an industrial-grade, fully sealed analog transmitter engineered for continuous, high-stability pH monitoring in demanding process environments. It operates on the electrochemical principle of potentiometric measurement: a pH-sensitive glass electrode and a stable reference electrode form a galvanic cell whose open-circuit potential follows the Nernst equation—approximately −59.16 mV per pH unit at 25 °C. The FJA-04 incorporates a third solution-ground electrode to suppress common-mode interference from ground loops and stray currents—critical for reliable operation in agitated reactors, wastewater basins, and municipal water treatment systems where grounding conditions are non-ideal. Unlike conventional pH meters, the FJA-04 features dual high-input-impedance circuitry (>10¹² Ω), enabling compatibility with both traditional liquid-filled reference electrodes and modern solid-state or gel-filled reference elements. Its integrated digital display supports field verification without external readout devices, while its robust epoxy-sealed housing meets IP65 ingress protection standards for dust- and splash-resistant operation in chemical plants, food processing lines, and effluent monitoring stations.

Key Features

• Fully sealed, IP65-rated enclosure designed for long-term deployment in humid, corrosive, or vibration-prone industrial settings
• Dual high-impedance input architecture supporting conventional Ag/AgCl reference electrodes as well as low-maintenance solid-state reference systems
• Integrated temperature compensation using a standard 10 kΩ NTC thermistor (25 °C nominal), eliminating manual correction and improving measurement traceability
• Configurable dual-output capability: isolated 4–20 mA current loop for PLC/DCS integration and 0–1400 mV voltage output (100 mV/pH) for local voltmeter interfacing
• Panel-mount form factor (96 × 96 × 112 mm) with standardized 92.7 × 92.7 mm cutout—compatible with DIN 43700-compliant mounting frames
• Calibration stability maintained via precision potentiometric offset (zero) and slope (span) adjustment circuits, factory-trimmed for minimal drift over time
• Support for two-point calibration using certified NIST-traceable buffer solutions (e.g., pH 4.01, 6.86, and 9.18) under static or flow-through conditions

Sample Compatibility & Compliance

The FJA-04 is validated for use across aqueous process streams including municipal wastewater, industrial cooling water, pharmaceutical rinse solutions, and chemical synthesis reactors. It complies with general requirements outlined in ISO 10523 (water quality — determination of pH) and ASTM D1293 (standard test method for pH of water). While not intrinsically safe or ATEX-certified, its design conforms to IEC 61000-6-2 (immunity to electrostatic discharge, fast transients, and conducted RF disturbances) and IEC 61000-6-4 (emission limits for industrial environments). For regulated industries, the device supports audit-ready calibration logs when paired with compliant smart displays featuring GLP/GMP-compliant event logging (e.g., timestamped calibration records, operator ID fields, and parameter change history)—though native data storage is not embedded in the transmitter itself.

Software & Data Management

The FJA-04 is an analog-only transmitter with no onboard microprocessor or firmware; thus, it does not include embedded software, cloud connectivity, or USB/Bluetooth interfaces. All configuration—including display resolution (0.01 or 0.1 pH), alarm thresholds, and output scaling—is performed locally via front-panel push-button interface on optional intelligent display modules (e.g., JY series or equivalent DIN-rail indicators). When integrated into larger SCADA or MES ecosystems, the 4–20 mA output provides linear, noise-immune transmission over distances up to 1 km (with appropriate shielded twisted-pair cabling and proper grounding practices). For FDA 21 CFR Part 11 compliance, users must implement external validation protocols for the entire measurement chain—including sensor certification, calibration documentation, and electronic record integrity—since the transmitter lacks built-in audit trails or electronic signature functionality.

Applications

• Real-time pH monitoring in activated sludge tanks, equalization basins, and tertiary clarification units
• Process control in chemical dosing systems (e.g., lime softening, acid neutralization, coagulant feed)
• In-line quality assurance during beverage bottling, dairy pasteurization, and biopharmaceutical buffer preparation
• Environmental compliance reporting for NPDES discharge permits and EPA Method 150.1 adherence
• Monitoring of boiler feedwater, condensate return lines, and closed-loop HVAC systems
• Field-deployable verification tool for laboratory cross-checks in GLP-regulated environmental testing labs

FAQ

What is the recommended calibration frequency for the FJA-04 in continuous operation?
Calibration interval depends on application severity: weekly for aggressive media (e.g., high-TDS wastewater), monthly for stable municipal water, and after each electrode replacement or mechanical disturbance to the “zero”/“slope” controls.
Can the FJA-04 be used with a pH electrode lacking a built-in temperature sensor?
Yes—external RTD or thermistor inputs are supported via dedicated terminals; however, automatic temperature compensation requires connection of a compatible 10 kΩ NTC sensor.
Is the 4–20 mA output intrinsically safe for hazardous area installation?
No—the FJA-04 is not certified for Class I Div 1 or ATEX Zone 0/1 environments; barrier-isolated signal conditioning is required for such deployments.
How is linearity verified across the full 0–14 pH range?
Linearity is confirmed during factory calibration using three NIST-traceable buffers (pH 4.01, 6.86, 9.18); end-user verification requires at minimum two-point calibration per ISO 7027-1 guidelines.
Does the transmitter support HART or other digital communication protocols?
No—the FJA-04 provides only analog outputs; for digital integration, users must select a HART-enabled smart transmitter or add a separate HART-to-analog converter.