JENCO Industrial Online pH Transmitter Series 691/692

Overview

The JENCO Industrial Online pH Transmitter Series 691/692 is a rugged, DIN-rail mountable process transmitter engineered for continuous, real-time monitoring of pH, oxidation-reduction potential (ORP), and temperature in industrial liquid streams. Based on potentiometric measurement principles, the transmitter interfaces with standard glass or combination pH electrodes (e.g., JENCO’s 6010 series or third-party ISO-compliant sensors) to convert electrode millivolt signals into stable, linearized digital outputs. Its dual-model architecture—691 with manual temperature compensation (MTC) and 692 with automatic temperature compensation (ATC)—enables flexible deployment across varying process conditions, from municipal wastewater treatment to chemical dosing loops and food-grade CIP rinse monitoring. Designed for long-term stability in harsh environments, the unit features galvanically isolated 4–20 mA analog output compliant with IEC 61000-4 electromagnetic immunity standards and suitable for integration into PLC-based SCADA systems.

Key Features

• DIN-standard 1/8 DIN aluminum enclosure (96 × 48 × 167 mm) with IP65 front panel rating for dust and water resistance
• Model 691: High-visibility LED display with dual-parameter readout (pH + temperature or ORP + temperature); Model 692: Backlit LCD display supporting multi-language menu navigation and real-time trend visualization
• Galvanically isolated 4–20 mA current output with selectable range mapping (e.g., 4–20 mA = 0–14 pH or user-defined span), configurable via front-panel keys or optional PC software
• Temperature compensation: 691 supports manual input via keypad (°C or °F); 692 integrates Pt100 or Pt1000 RTD inputs for automatic compensation per NIST-traceable thermistor algorithms
• Calibration support for two-point (asymmetric) pH calibration with slope and offset verification; ORP calibration via standard redox buffer solutions (e.g., Zobell’s solution)
• Configurable alarm thresholds with relay output (optional module) for high/low pH, sensor fault, or temperature deviation alerts

Sample Compatibility & Compliance

The Series 691/692 is compatible with all industry-standard pH and ORP sensors featuring BNC, DIN, or screw-terminal connections. It supports operation in conductive aqueous media with conductivity ≥50 µS/cm and is rated for use in non-explosive atmospheres (Class I, Division 2, Group A–D per NEC Article 500). The transmitter complies with ISO/IEC 17025 traceability requirements when used with certified reference buffers (e.g., NIST SRM 186, 188, 4697). Its analog output meets ANSI/ISA-50.00.01 signal integrity specifications, and firmware supports audit-ready calibration logging for GLP/GMP-aligned operations where documentation of calibration history, operator ID, and environmental conditions is required.

Software & Data Management

Configuration and diagnostics are performed via intuitive front-panel controls or optionally through JENCO’s Windows-based PC utility (JENCO ConfigTool v3.2), which enables batch parameter export/import, firmware updates, and timestamped calibration record generation. All configuration changes—including sensor type selection, temperature coefficient (α), and linearization settings—are stored in non-volatile memory with battery-backed retention (>10 years). The device supports Modbus RTU over RS-485 (optional module) for integration into centralized asset management platforms. While the transmitter itself does not store historical data, its 4–20 mA output is fully compatible with DCS historian systems that comply with FDA 21 CFR Part 11 for electronic records and signatures when deployed with appropriate system-level validation.

Applications

• Continuous pH monitoring in municipal and industrial wastewater treatment plants (influent, aeration basins, effluent discharge)
• Chemical feed control for coagulant/flocculant dosing, chlorine stabilization, and acid/base neutralization
• Pharmaceutical water-for-injection (WFI) and purified water (PW) loop monitoring per USP and EP 2.2.43
• Food and beverage processing: CIP rinse validation, dairy fermentation control, and juice acidification
• Electroplating bath management, where precise ORP tracking ensures optimal redox potential for chromium passivation or nickel plating
• Boiler feedwater and condensate pH surveillance in power generation facilities per ASTM D1066 and ASME PTC 19.11

FAQ

Does the Series 692 support automatic temperature compensation with all pH electrodes?
Yes—provided the connected electrode includes an integrated Pt100 or Pt1000 temperature sensor and uses a 3- or 4-wire connection compatible with the transmitter’s ATC input circuit.
Can the 4–20 mA output be re-ranged for non-standard pH spans (e.g., 4–20 mA = 5.5–8.5 pH)?
Yes—both models allow full user-defined span mapping via the setup menu, including asymmetric ranges and inverted scaling.
Is the transmitter suitable for high-pressure inline applications?
The transmitter itself is not pressure-rated; it must be installed remotely from the process line, interfacing with pressure-rated pH/ORP sensors mounted in sanitary or threaded process housings (e.g., Tri-Clamp or NPT).