Wireless Differential Pressure Measurement for Difficult-to-Wire Applications
The Yokogawa EJX118B is designed for differential pressure measurement where conventional wired installation is inconvenient or where remote diaphragm seals are required to isolate the pressure-sensing assembly from the process medium.
Unlike a conventional differential pressure transmitter connected directly to the process, the EJX118B uses remote diaphragm seals connected through fill-fluid capillaries. This arrangement helps protect the sensing assembly when the process involves challenging media or when the measurement point requires a remote seal configuration.
The wireless transmitter communicates using the ISA100.11a industrial wireless protocol and operates from an internal battery. This removes the need for conventional signal wiring to the transmitter, which can significantly simplify installation at remote or difficult-to-access measurement points.
Why Choose EJX118B?
The main advantage of the EJX118B is not simply wireless communication. It combines wireless instrumentation and remote diaphragm sealing in one measurement solution.
This makes it particularly useful when:
- Signal cabling is difficult, expensive or impractical
- Measurement points are far from the control system
- Existing plants need additional measurement points
- Process media should be isolated from the transmitter sensing assembly
- Conventional impulse piping may be unsuitable
- Tank level measurement requires remote diaphragm seals
- Distributed pressure or flow monitoring is required
Yokogawa specifically highlights applications including flow measurement of liquids, gases and steam, liquid level, density and pressure measurement.
Key Features
- Wireless differential pressure transmitter with remote diaphragm seals
- ISA100.11a wireless communication
- Internal battery-powered operation
- Long-life lithium-thionyl chloride battery design
- Wireless transmission of both process variables and setting parameters
- Selectable process-value update interval from 0.5 second to 60 minutes
- Remote diaphragm seals connected through fill-fluid capillaries
- Suitable for liquid, gas and steam flow measurement
- Suitable for liquid level, density and differential pressure measurement
- 260 ms approximate response time for M and H capsules under normal temperature conditions
- Reference accuracy of ±0.15% of span when the measurement span is within the specified accuracy region
- Wireless security using AES-128 encryption
- 2.4 GHz ISM-band wireless communication
Wireless Communication and Battery Operation
The EJX118B uses the ISA100.11a wireless protocol with a 2.4 GHz ISM-band radio system. The transmitter can publish measured process values at intervals selectable from 0.5 seconds to 60 minutes, allowing the update rate to be matched to the application.
The current Yokogawa General Specifications indicate a dedicated 7.2 V, 19 Ah battery pack. Typical battery life is specified as up to 10 years at a 30-second update interval or approximately 5 years at a 10-second update interval under stated reference conditions. Actual battery life depends on operating conditions and configuration.
Remote Diaphragm Seal Design
The diaphragm seal prevents the process medium from entering the transmitter's pressure-sensing assembly. The seal is connected to the transmitter through capillaries containing fill fluid.
This configuration is particularly useful when direct connection to the process is undesirable or when the transmitter needs to be positioned away from the process connection. Yokogawa provides multiple diaphragm seal configurations, including flush, extended and combination types.
Typical Applications
Tank Level Measurement
Remote diaphragm seals can be used for differential pressure-based level measurement, especially where the transmitter cannot be mounted directly at the tank connection.
Flow Measurement
The EJX118B can be used with suitable primary flow elements for differential pressure flow measurement of liquids, gases and steam.
Chemical Process Monitoring
Wireless communication can simplify the addition of pressure measurement points in existing chemical processing facilities where new signal cables are difficult to install.
Oil & Gas Applications
Wireless pressure monitoring can be useful at distributed or remote measurement locations, including applications where conventional cabling would increase installation complexity.
Plant Expansion and Retrofit
The wireless architecture is particularly attractive when adding measurement points to an operating facility without extensive new cable infrastructure. Yokogawa application examples include chemical plants, gas wells, water treatment plants and distributed tank monitoring.
EJX118B vs. Conventional Wired Differential Pressure Transmitter
The biggest difference is the communication and installation architecture.
A conventional transmitter normally requires signal wiring between the field device and the control system. The EJX118B instead uses wireless communication and internal battery power, reducing the amount of field cabling required.
The EJX118B also integrates remote diaphragm seals, so it is better suited to applications where process isolation and remote mounting are important.
Frequently Asked Questions
What is the Yokogawa EJX118B used for?
The EJX118B is used for differential pressure measurement and can also be applied to liquid level, flow, density and pressure measurement for liquids, gases and steam.
What makes the EJX118B different from a standard EJX110B?
The EJX118B adds a remote diaphragm seal system to the wireless differential pressure transmitter. This allows the process medium to be isolated from the sensing assembly and provides greater flexibility for challenging process connections.
Is the EJX118B a completely wireless pressure measurement solution?
The measurement signal is transmitted wirelessly using ISA100.11a, and the transmitter can operate from its internal battery. However, a complete wireless installation still requires a compatible wireless infrastructure such as the appropriate gateway and network configuration.
What is ISA100.11a?
ISA100.11a is an industrial wireless communication standard designed for reliable wireless communication in process automation environments. The EJX118B uses this protocol for wireless transmission of process information and device parameters.
How long does the EJX118B battery last?
Under Yokogawa's specified reference conditions, typical battery life is approximately 10 years at a 30-second update interval or 5 years at a 10-second update interval. Actual battery life can vary with update rate, operating conditions and configuration.
How fast can the EJX118B update its measurement?
The process-value publication interval can be selected from 0.5 second to 60 minutes, allowing the wireless update rate to be adjusted according to the application.
Can the EJX118B measure tank level?
Yes. Differential pressure measurement with remote diaphragm seals is commonly used for tank level measurement. The EJX118B is designed for liquid-level applications as well as flow, density and pressure measurement.
Why use a remote diaphragm seal?
A remote diaphragm seal isolates the transmitter from the process medium. This can be valuable when direct process connection is unsuitable or when the process conditions require the sensing assembly to be separated from the process connection.
Can the EJX118B measure flow?
Yes. With an appropriate primary flow element, the EJX118B can be used for differential pressure flow measurement of liquids, gases and steam. Its output can also be configured for linear or square-root operation.
Is the EJX118B suitable for retrofit projects?
Yes. Eliminating conventional signal cabling is one of the main advantages of the wireless design. It can be particularly useful when adding measurement points to existing facilities where installing new cables would require significant construction work. Yokogawa provides application examples for plant monitoring and retrofit-style wireless instrumentation.
