Original Yokogawa EJA438E with Remote Diaphragm Seal - DA Diaphragm Sealed Gauge Pressure Transmitter

Overview

The Yokogawa EJA438E is a gauge-pressure transmitter in which the pressure sensing element is connected to the process via a remote diaphragm seal and capillary filled with fluid. This remote-seal arrangement makes it suitable for harsh, viscous, high-temperature or corrosive media where direct mounting of the sensor may not be feasible.

Importantly: the model has been officially discontinued by the manufacturer. When you see “(DISCONTINUED)” in the specification or product heading, it means you’ll likely need to plan for replacement or alternative sourcing/stocking.

Key Features & Specifications

Here are some of the major features and technical highlights:

• Measurement range & span: For example “A” span category: 0.06 to 3.5 MPa (≈ 8.6 to 500 psi) with range from –0.1 to +3.5 MPa. For the “B” category (flush/extended type) span from 0.46 to 16 MPa etc.
• Accuracy: Reference accuracy of calibrated span is typically ±0.2% of span (for certain spans) in the standard configuration.
• Response time: Approx. 200 ms (with zero software damping) including nominal dead time of 45 ms.
• Output / Communication options: 4-20 mA DC with digital superimposed communications (HART/BRAIN), also versions with 1-5 V output + HART, or digital bus (FOUNDATION Fieldbus, PROFIBUS PA).
• Self diagnostics / advanced features: The transmitter supports local parameter setting (LPS via buttons or detail configuration), signal characterizer (10-segment for 4-20 mA), capillary fill-fluid density compensation (for the remote seal/capillary fluid effect) etc.
• Diaphragm seal remote system: The remote diaphragm seal prevents the process fluid from entering the sensor assembly; it's connected via capillary filled with appropriate fluid. This config enables measurement of challenging media (high viscosity, high temperature, corrosives, etc).
• SIL certification: In standard (non-Fieldbus/PROFIBUS) configuration, the EJA-E series meets SIL 2 safety requirements.

Use-Case / Application Context

Because of the remote diaphragm seal, the EJA438E is especially appropriate for process applications where:

• The process fluid is high temperature, viscous, dirty, or contains solids or aggressive chemicals, and direct exposing of the sensor is undesirable.
• There is a requirement for high accuracy gauge pressure measurement in a harsh environment.
• The process connection may need to be physically remote from the transmitter electronics (for example to keep electronics away from high temperature or hazardous area).
• A standard 4-20 mA loop (with HART) or fieldbus communication is used in a process control / instrumentation system.

You’ll often find such transmitters in industries like oil & gas, petrochemical, chemical, power generation, or other heavy processing plants.

Discontinuation and Replacement

It is important to note that the EJA438E has been discontinued. For example:

• The manufacturer page states it is “DISCONTINUED” and replaced by the model series Yokogawa EJXC80A or EJAC80E Diaphragm Seal Systems.
• Being discontinued means: no new production, limited spare/stock availability, potential end of full support or long-term availability of original parts.
• For replacement, upgrade or future procurement you should engage with Yokogawa or their authorised distributor to find the best current equivalent, check compatibility, consider retrofit costs etc.

Considerations for South Africa / Local Market

Since you are based in Benoni, Gauteng, South Africa, some local notes:

• Because the transmitter is discontinued, check the available local stock or import lead times. Spare parts may be limited.
• Ensure you have local support for calibration, stamping, certification (if required) and any explosion/zone hazardous approvals relevant in South African/ SADC environment.
• When replacing, check that the replacement product has suitable local approvals (ATEX/IECEx, South African standards) for your installation.
• Capillary remote seal systems mean installation care is important: proper mounting, correct fill fluid, capillary routing, temperature effects to be considered especially in hotter ambient conditions common in Gauteng region.
• Consider whether you can standardise on a newer model (replacement) across multiple installations for ease of maintenance and spares.