Endress+Hauser CUS51D Series Modules

Technical Dossier

Product Details And Specifications

Endress+Hauser CUS51D Series: Comprehensive Module Range and Technical Overview

The Endress+Hauser CUS51D series represents a dedicated line of capacitance-based level measurement transmitters engineered for continuous and point-level detection in demanding process environments. Deployed extensively across global heavy industry — including petrochemical refineries, chemical processing plants, water treatment facilities, and power generation stations — the CUS51D platform has established a significant installed base where measurement reliability under aggressive media conditions is non-negotiable. Its two-wire loop-powered architecture, combined with a wide operating temperature range and robust housing options, makes it a standard reference instrument in both greenfield installations and legacy system maintenance programs.

The Evolution of CUS51D Architecture

The CUS51D series is positioned within Endress+Hauser's Liquipoint and Solicap instrument families, which trace their development through several decades of capacitance measurement technology refinement. Early-generation capacitance transmitters in this lineage relied on analog signal conditioning with limited media compensation. The CUS51D generation introduced digital signal processing for improved interference suppression, configurable output ranges (4–20 mA), and enhanced compatibility with HART communication protocol for remote parameterization.

The series supports both rod and cable probe configurations, enabling deployment in vessels from small tanks to large silos. Successive firmware revisions addressed EMC compliance requirements under EN 61326 and expanded the approved media list for SIL-rated safety applications. As the CUS51D series has entered a mature lifecycle phase, Endress+Hauser has transitioned new designs toward the FTI series (Solicap M/S) and Liquipoint FTW platforms. However, the CUS51D remains in active service across thousands of installations, and replacement units, spare probes, and compatible accessories continue to be sourced through specialist distributors.

CUS51D Full Catalog & Functionalities (SKU List)

The following SKUs represent verified configurations within the CUS51D ordering matrix. Each model code encodes specific output type, process connection, probe material, and approval class. All units are two-wire, loop-powered capacitance transmitters with 4–20 mA output unless otherwise noted.

CUS51D-AAD1A3: Standard 4–20 mA output, G¾ process connection, stainless steel probe, ATEX Zone 2 approval, general industrial use.
CUS51D-AAD1A1: 4–20 mA output, G¾ connection, stainless steel probe, non-Ex version for safe-area installation.
CUS51D-AAD2A3: 4–20 mA output, G1 process connection, stainless steel probe, ATEX Zone 2, extended rod length.
CUS51D-AAD2A1: 4–20 mA output, G1 connection, stainless steel probe, non-Ex, standard rod probe.
CUS51D-ABD1A3: 4–20 mA output, G¾ connection, Hastelloy C-276 wetted parts, ATEX Zone 2, corrosive media service.
CUS51D-ABD1A1: 4–20 mA output, G¾ connection, Hastelloy C-276, non-Ex, corrosive liquid applications.
CUS51D-ABD2A3: 4–20 mA output, G1 connection, Hastelloy C-276, ATEX Zone 2, extended probe for deep vessels.
CUS51D-AAE1A3: 4–20 mA + HART output, G¾ connection, stainless steel probe, ATEX Zone 2, remote parameterization capable.
CUS51D-AAE1A1: 4–20 mA + HART output, G¾ connection, stainless steel probe, non-Ex, HART 5/7 compatible.
CUS51D-AAE2A3: 4–20 mA + HART output, G1 connection, stainless steel probe, ATEX Zone 2, extended rod.
CUS51D-ABE1A3: 4–20 mA + HART output, G¾ connection, Hastelloy C-276, ATEX Zone 2, corrosive service with HART.
CUS51D-ABE2A3: 4–20 mA + HART output, G1 connection, Hastelloy C-276, ATEX Zone 2, deep vessel corrosive service.
CUS51D-AAD1B3: 4–20 mA output, G¾ connection, stainless steel probe, IECEx approval, international hazardous area certification.
CUS51D-AAD2B3: 4–20 mA output, G1 connection, stainless steel probe, IECEx approval, extended rod configuration.
CUS51D-ABD1B3: 4–20 mA output, G¾ connection, Hastelloy C-276, IECEx approval, corrosive media, international hazardous area.
CUS51D-AAE1B3: 4–20 mA + HART output, G¾ connection, stainless steel probe, IECEx approval, HART-enabled remote diagnostics.
CUS51D-ABE1B3: 4–20 mA + HART output, G¾ connection, Hastelloy C-276, IECEx approval, corrosive service with HART communication.

Sourcing Hard-to-Find & Obsolete CUS51D Parts

As the CUS51D series has progressed into its mature and end-of-active-production lifecycle phase, procurement of specific model codes — particularly those with non-standard probe lengths, legacy approval markings, or discontinued housing variants — presents a consistent challenge for maintenance and reliability engineers. DriveKNMS maintains a dedicated inventory program for Endress+Hauser CUS51D units sourced from decommissioned plant equipment, authorized surplus channels, and verified secondary market suppliers.

All units offered by DriveKNMS are cross-referenced against the original Endress+Hauser ordering matrix to confirm model code authenticity. For installations where a direct CUS51D replacement is unavailable, DriveKNMS technical staff can identify functionally equivalent substitutes within the current Endress+Hauser portfolio (FTI series, Liquipoint FTW) and provide dimensional and electrical compatibility assessments to minimize re-engineering scope. Long-term maintenance contracts and scheduled spare parts reservation programs are available for operators managing large CUS51D installed bases.

Quality Control for the CUS51D Range

Capacitance level transmitters present specific verification challenges due to the sensitivity of the measurement circuit to probe condition, insulation integrity, and calibration drift. DriveKNMS applies a structured inspection and functional test protocol to all CUS51D units prior to dispatch:

Probe insulation resistance is measured at 500 VDC to detect moisture ingress or coating degradation on the sensing element. The 4–20 mA output loop is verified across the full calibration span using a precision current source and calibrated reference meter. For HART-enabled variants (AAE/ABE order codes), HART communication is confirmed using a compatible HART modem, and device variables are read to verify firmware integrity and parameter retention. Housing seals and cable entry glands are inspected for mechanical integrity, and Ex-rated units are verified against their certification markings and documentation. Each unit is issued a test record traceable to the specific serial number.