Product Overview

The Yokogawa SC25V-ALP25-120 represents the pinnacle of liquid analysis technology, integrating four discrete sensing elements into a single, robust 12mm body. This combined electrode captures pH levels, reference potentials, and temperature via an onboard Pt1000 RTD, while the integrated Titanium liquid earth eliminates measurement drift caused by stray ground currents. Engineered specifically for harsh industrial processes, the SC25V excels in high-temperature environments and chemically aggressive media where standard sensors fail. Its specialized AR-Glass and PEEK construction provide a durable barrier against corrosion, ensuring precise analytical data for critical applications like cooling tower water management, chemical dosing, and wastewater treatment. By delivering a stable, low-impedance signal through its Variopin connector, this sensor enables real-time monitoring of fluid chemistry with laboratory-grade accuracy in a field-hardened format.

Technical Configuration

The SC25V-ALP25-120 model string defines a specific set of hardware characteristics optimized for specialized process conditions and safety requirements.

Model Suffix Analysis: SC25V-ALP25-120

SC25V: This identifies the 12mm combined sensor series equipped with the standard Variopin (VP) waterproof connector, ensuring secure signal transmission in humid or wash-down environments.

ALP25: This code designates the specialized "Alkali Resistant" glass type. The ALP25 sensor chemistry withstands high-temperature operation and resists chemical erosion in processes with high pH values or high salt concentrations.

120: Specifies the immersion length of the sensor body. The 120 mm length follows the standard laboratory and industrial DIN mounting dimensions, making it compatible with a wide range of retractable or flow-through fittings.

Intrinsically Safe (IS): The module carries global certifications including ATEX, IECEx, and FM, allowing for safe deployment in Zone 0 or Class I, Division 1 hazardous areas.

Technical Specifications

Engineering Advantages

The SC25V-ALP25-120 thrives in extreme process conditions where electrolytic depletion usually limits sensor life. Its PTFE reference junction provides a large surface area that resists fouling and clogging, maintaining a stable junction potential even in oily or high-solid fluids. The use of PEEK for the sensor head provides mechanical strength far superior to standard plastic sensors, protecting the internal electronics from physical stress.

Furthermore, the Titanium liquid earth functions as a shield against process noise. In modern plants with variable frequency drives (VFDs) and heavy electrical loads, stray voltages often cause pH readings to fluctuate. This electrode drains those currents to ground, ensuring that the CENTUM VP or standalone transmitter receives a pure, noise-free analytical signal. This makes it a vital component for high-reliability loops in the pharmaceutical and petrochemical industries.

Installation Guide

Correct mechanical installation and electrical grounding guarantee the long-term accuracy of the SC25V sensor.

Mounting Orientation

Install the sensor at an angle of at least 15° above the horizontal plane. This orientation ensures that the internal electrolyte remains in contact with the pH glass bulb and prevents air bubbles from trapping in the reference chamber.

Variopin Connection

Ensure the Variopin connector is completely dry before mating the cable. While the VP connector provides an IP68-rated seal, moisture trapped inside the pins during installation will cause high-impedance leakage, leading to significant measurement drift.

Storage and Conditioning

Never allow the pH bulb to dry out. If the sensor is removed from the process for maintenance, store it in a 3.3M KCl solution. For first-time installation, soak the ALP25 glass in a buffer solution for at least 24 hours to fully hydrate the measuring membrane.

Technical FAQs

Q1: What makes the ALP25 glass different from standard pH glass?

A1: The ALP25 glass is specifically formulated to resist "alkaline error" at high pH levels and maintains its structural integrity at temperatures up to 130°C, where standard glass would quickly dissolve or lose sensitivity.

Q2: Does this sensor support digital communication like SENCOM?

A2: No, the SC25V-ALP25-120 is an analog sensor. It outputs a millivolt signal for pH and a resistance signal for temperature, making it compatible with any standard high-impedance pH transmitter.

Q3: How often should I calibrate the SC25V-ALP25-120?

A3: Calibration frequency depends on the process aggressiveness. For high-temperature chemical applications, we recommend a two-point buffer calibration weekly to compensate for natural sensor aging and glass impedance changes.

Q4: Can this electrode be used in hazardous areas?

A4: Yes. This module is certified for use in intrinsically safe (IS) environments when used with an approved Yokogawa barrier or transmitter, meeting ATEX and IECEx standards.