Wireless Absolute Pressure Measurement
The Yokogawa EJX310B is a high-performance absolute pressure transmitter in the EJX-B wireless series. It uses Yokogawa's single-crystal silicon resonant sensor technology and measures pressure relative to an absolute vacuum reference rather than atmospheric pressure.
This makes absolute pressure measurement useful when changes in atmospheric pressure could affect the accuracy or interpretation of a process measurement. The EJX310B is available with several measurement capsules covering low absolute pressure through higher-pressure applications.
Why Absolute Pressure Matters
Absolute pressure is different from gauge pressure because the measurement reference is a vacuum rather than the surrounding atmosphere.
This is particularly important in applications such as vacuum systems, pressure-controlled processes, distillation, evaporation and other processes where atmospheric pressure changes should not become part of the measurement.
The EJX310B provides this measurement capability while adding the flexibility of an industrial wireless connection.
Wireless Installation Without Conventional Signal Cabling
One of the main advantages of the EJX310B is its wireless architecture.
The transmitter uses ISA100.11a communication and internal battery power, allowing process measurements to be transmitted without conventional signal cabling between the field transmitter and the control system. This can reduce installation work when measurement points are remote, widely distributed or difficult to reach with new cables.
The wireless network can also transmit setting parameters. Infrared communication is provided for wireless network configuration and parameter setting, helping simplify device commissioning.
Key Features
- Wireless absolute pressure transmitter
- Single-crystal silicon resonant sensor
- ISA100.11a wireless communication
- Internal battery-powered operation
- Process values and setting parameters transmitted wirelessly
- Selectable process-value update interval from 0.5 second to 60 minutes
- Long-life battery design using high-capacity lithium-thionyl chloride batteries
- Infrared communication for wireless network configuration
- Measurement capsules from 0.5–10 kPa abs to 0.08–16 MPa abs
- Reference accuracy up to ±0.04% of span for M, A and B capsules within the specified accuracy region
- L capsule reference accuracy of 0.075% of span
- 150 ms response time
- Long-term stability of ±0.1% of URL per 10 years for the applicable EJX B series pressure transmitter configurations
Measurement Range and Capsule Selection
The EJX310B is available in four measurement span capsules:
- L: 0.5 to 10 kPa abs
- M: 1.3 to 130 kPa abs
- A: 0.0175 to 3.5 MPa abs
- B: 0.08 to 16 MPa abs
The correct capsule should be selected according to the actual absolute pressure range, required span and process conditions.
For procurement, the complete model code is important because capsule selection, wetted materials, process connection, display and hazardous-area requirements can change the final configuration.
Battery-Powered Wireless Operation
The EJX310B is designed for low-power wireless operation using high-capacity lithium-thionyl chloride batteries.
Yokogawa's specifications indicate typical battery life of approximately 10 years at a 30-second update interval or 5 years at a 10-second update interval under specified reference conditions. Actual battery life depends on update interval, operating environment and configuration.
This makes the EJX310B particularly attractive for distributed monitoring points where installing and maintaining conventional signal cables would add significant infrastructure work.
Typical Applications
Absolute Pressure Monitoring
The EJX310B is suitable for industrial processes where pressure needs to be measured independently of atmospheric pressure.
Vacuum and Low-Pressure Applications
Absolute pressure measurement is useful when the process operates under vacuum or when atmospheric pressure variations could influence a gauge-pressure measurement.
Process Pressure Monitoring
The transmitter can be installed at distributed pressure monitoring points in chemical, power, oil and gas, water and wastewater and other process industries.
Tank and Level Applications
Differential pressure is not required for every level application. Where the process measurement arrangement requires an absolute pressure reference, an absolute pressure transmitter can provide useful process information. Yokogawa also lists liquid-level and density applications among the broader EJX-B wireless transmitter applications.
Plant Expansion and Retrofit
Wireless communication can be particularly useful when adding new measurement points to an existing facility. Yokogawa provides application examples covering chemical plants, gas wells, water treatment plants and diesel tank monitoring.
Frequently Asked Questions
What is the Yokogawa EJX310B used for?
The EJX310B is primarily a wireless absolute pressure transmitter for industrial process measurement. Yokogawa also lists applications involving liquid, gas and steam processes, liquid level, density and flow-related measurement.
What is the difference between absolute pressure and gauge pressure?
Absolute pressure uses a vacuum as the reference point, while gauge pressure uses atmospheric pressure as the reference.
Absolute pressure is therefore useful when atmospheric pressure variations should not affect the measurement, such as in vacuum and certain pressure-control applications.
Why choose the EJX310B instead of a conventional wired absolute pressure transmitter?
The main difference is the communication architecture. The EJX310B uses ISA100.11a wireless communication and internal battery power, eliminating conventional signal wiring at the transmitter.
This can be especially useful for remote measurement points, plant expansion and retrofit projects where installing new signal cables would be difficult or expensive.
Is the EJX310B completely wireless?
The measurement transmitter communicates wirelessly and can operate from its internal battery. However, a complete installation still requires compatible ISA100 wireless infrastructure, such as the appropriate gateway and network configuration.
How fast can the EJX310B update its measurement?
The measured process value can be published wirelessly at selectable intervals from 0.5 second to 60 minutes. The appropriate update interval depends on the dynamics of the process and the required monitoring performance.
How long does the EJX310B 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 varies with operating conditions and configuration.
What measurement ranges are available?
The EJX310B provides four capsule options covering absolute pressure spans from 0.5–10 kPa abs up to 0.08–16 MPa abs. The correct capsule should be selected according to the required measurement range and process conditions.
How accurate is the EJX310B?
For the M, A and B capsules, the reference accuracy can be ±0.04% of span when the specified measurement-span conditions are met. The L capsule has a reference accuracy of 0.075% of span. Actual performance depends on the selected capsule, rangedown and operating conditions.
What is ISA100.11a?
ISA100.11a is an industrial wireless communication standard designed for process automation. The EJX310B uses ISA100.11a for wireless transmission of process data and device parameters. Yokogawa specifies a 2.4 GHz ISM frequency band, 250 kbps data rate and AES-128 wireless security for its wireless transmitter platform.
Can the EJX310B be used in a retrofit project?
Yes. Wireless communication can reduce the need for new signal cabling when additional pressure measurement points are added to an existing plant. Yokogawa provides wireless application examples in chemical plants, gas wells, water treatment and tank monitoring.
What is the difference between EJX310B and EJX210B?
The EJX310B is a wireless absolute pressure transmitter, while the EJX210B is a wireless flange-mounted differential pressure transmitter primarily intended for level and density measurement, particularly with solidifying or precipitating liquids.
The two models therefore solve different measurement and installation requirements.
What is the difference between EJX310B and EJX510B?
Both are wireless absolute pressure transmitters, but their mechanical mounting configurations are different.
The EJX310B is the traditional-mount absolute pressure configuration, while the EJX510B is the in-line mount absolute pressure configuration. The choice depends mainly on the required process connection and installation arrangement.
