Multivariable Measurement for High Static Pressure Applications
The Yokogawa EJX930A is a multivariable transmitter developed specifically for applications where high static pressure is an important part of the measurement challenge.
Instead of using separate transmitters for differential pressure, static pressure, and temperature together with an external flow computer, the EJX930A integrates these measurement functions into one device. It measures differential pressure, static pressure, and external temperature, then uses an onboard flow computer to calculate fully compensated mass flow.
Why Choose the EJX930A?
The main reason to select the EJX930A over a general multivariable transmitter is its high static pressure capability.
The transmitter supports a maximum working pressure of 4,500 psi and is designed for applications where both flow measurement and high process pressure must be considered. The current Yokogawa specifications list ±0.04% of span reference accuracy for DP and ±0.1% of span for static pressure under the specified conditions.
This makes the EJX930A particularly suitable when conventional multivariable measurement needs to be combined with demanding high-pressure process conditions.
Three Process Variables in One Transmitter
The EJX930A measures:
- Differential pressure (DP)
- Static pressure (SP)
- External process temperature (ET)
These measurements can be used individually as process variables or together for flow calculation.
For mass flow applications, the onboard flow computer uses the measured process conditions together with programmed primary-device and fluid parameters to calculate compensated flow.
Fully Compensated Mass Flow Calculation
For DP-based flow measurement, changes in pressure, temperature, density, and other flow factors can influence the calculated flow rate.
The EJX930A can dynamically compensate parameters such as:
- Discharge coefficient
- Primary device bore
- Upstream pipe diameter
- Gas expansion factor
- Fluid density
- Fluid viscosity
The FSA120 FlowNavigator software is used to configure these parameters for the flow calculation.
This approach allows the transmitter to perform the flow calculation using actual process measurements rather than relying only on fixed operating assumptions.
High Static Pressure Capability
The EJX930A is designed for high-static-pressure environments and supports M and H differential pressure capsules.
The current General Specification lists:
- Differential pressure span: 1 to 100 kPa (M)
- Differential pressure span: 5 to 500 kPa (H)
- Static pressure measurement up to 32 MPa absolute
- Sealed gauge static pressure measurement up to 32 MPa
- Maximum working pressure: 4,500 psi
- DP reference accuracy: ±0.04% of span
- Static pressure reference accuracy: ±0.1% of span
- DP response time: 250 ms
- Static pressure response time: 200 ms
Long-Term Stability
The EJX930A provides long-term DP stability of ±0.1% of URL per 15 years under normal operating conditions specified by Yokogawa.
For applications where measurement stability is important over long operating periods, this can help reduce the need for frequent re-zeroing and maintenance intervention.
Communication and System Integration
Depending on configuration, the EJX930A supports:
- HART
- FOUNDATION Fieldbus
- RS485 Modbus
The Modbus version can provide multiple process values to external systems such as flow computers or RTUs. HART and FOUNDATION Fieldbus versions can also support multivariable and mass-flow measurement functions according to the selected configuration.
Saturated Steam Measurement
For HART 7 equipment revision 12 or later, Yokogawa provides a Saturated Steam Mode.
In this mode, the transmitter can calculate steam temperature from static pressure using the IAPWS-IF97 steam table. This allows saturated steam flow measurement without connecting a separate external thermometer in the supported configuration.
Key Features
- Designed specifically for high static pressure applications
- Measures differential pressure, static pressure, and external temperature
- Onboard flow computer for compensated mass flow calculation
- DPharp single-crystal silicon resonant sensor technology
- Maximum working pressure up to 4,500 psi
- DP reference accuracy up to ±0.04% of span
- Static pressure reference accuracy up to ±0.1% of span
- DP long-term stability of ±0.1% URL per 15 years
- HART, FOUNDATION Fieldbus, and RS485 Modbus options
- Dynamic flow compensation
- Compatible with FSA120 FlowNavigator configuration software
- Saturated steam mode available with supported HART 7 revision
Typical Applications
The EJX930A is suited to DP-based flow measurement where high static pressure is present, including:
- High-pressure gas flow measurement
- High-pressure steam flow measurement
- Oil and gas processing
- Chemical and petrochemical processes
- Power generation
- Utility and energy systems
- High-pressure pipeline flow monitoring
- Orifice flow measurement
- Nozzle and Venturi flow measurement
- Averaging pitot tube applications
Its high-static-pressure design makes it particularly useful when conventional multivariable transmitters may not provide the required pressure capability.
FAQ
What is the EJX930A?
The EJX930A is a multivariable transmitter designed specifically for high static pressure applications. It measures differential pressure, static pressure, and external temperature and can use these values to calculate compensated mass flow.
What makes the EJX930A different from the EJX910A?
The main difference is the intended pressure environment.
EJX910A is the general multivariable model, while EJX930A is specifically designed for high static pressure applications. The EJX930A supports a maximum working pressure of 4,500 psi.
Is the EJX930A a flowmeter?
It is better described as a multivariable transmitter with an onboard flow computer.
The actual primary flow element—such as an orifice plate, nozzle, Venturi, or averaging pitot tube—creates the differential pressure. The EJX930A measures the required process variables and calculates the compensated flow.
What does the EJX930A measure?
The transmitter measures:
- Differential pressure
- Static pressure
- External process temperature
The measured values can then be used for compensated mass flow calculation.
What is the maximum working pressure of the EJX930A?
The current Yokogawa specification lists a maximum working pressure of 4,500 psi for the EJX930A.
Can the EJX930A measure gas flow?
Yes. It is suitable for DP-based gas flow measurement, particularly where pressure and temperature compensation are important and high static pressure is present.
The transmitter can dynamically use parameters such as density, viscosity, gas expansion factor, primary-device bore, and discharge coefficient in its flow calculation.
Can the EJX930A measure steam flow?
Yes. The EJX930A can be used for DP-based steam flow measurement.
With supported HART 7 equipment revision 12 or later, its Saturated Steam Mode can calculate steam temperature from static pressure using IAPWS-IF97, allowing supported saturated steam applications to operate without an external temperature sensor.
Does the EJX930A need a separate flow computer?
Not when configured for its mass-flow function.
The EJX930A has an onboard flow computer that can calculate compensated mass flow using the measured DP, static pressure, temperature, and configured flow parameters.
What software is used to configure the EJX930A flow calculation?
Yokogawa provides FSA120 FlowNavigator for configuring the flow calculation.
The software supports parameters including the primary device, discharge coefficient, pipe diameter, gas expansion factor, density, and viscosity.
What primary flow elements can be used with the EJX930A?
The EJX930A can be applied with DP-based primary devices such as orifice plates, nozzles, Venturi tubes, and averaging pitot tubes, depending on the measurement application and configuration.
Is the EJX930A suitable for high-pressure oil and gas applications?
Yes. Its high-static-pressure capability makes it suitable for demanding process applications where DP flow measurement is combined with high line pressure. Yokogawa specifically positions the EJX930A for high static pressure applications.
What communication options are available?
Depending on the selected configuration, the EJX930A is available with HART, FOUNDATION Fieldbus, or RS485 Modbus communication.
What is the advantage of using one EJX930A instead of separate transmitters?
The EJX930A integrates multiple measurement functions and flow calculation into one device.
This can reduce the need for separate DP, static-pressure, temperature, and flow-computing equipment, potentially simplifying installation, system integration, and maintenance.
