When you hear discussions about “the cloud” you often also hear about “the edge” where higher resolution processing can be performed. For manufacturers and producers, this edge may extend to the instrumentation itself measuring and controlling the process.
In a Control Engineering IIoT for Engineers supplement article, Extend edge data gathering with multivariable instruments, Emerson’s Connor Oberle describes how many measurement devices are capable of providing more than one measurement.
These additional measurements can be used for more than process control and monitoring to include inputs to Industrial Internet of Things (IIoT) applications. Connor noting that different instruments have different capabilities:
The simpler the instrument, such as those used to measure temperature, the fewer variables. On the other hand, complex instruments such as differential pressure (DP) flow meters often measure or infer multiple process variables.
He explains that some sensors require an additional measurement for the accuracy of the primary sensor.
For example, many sensors used to measure pressure (piezoresistive, capacitive, and others) require compensation for temperature, so the transmitter must include an internal temperature sensor as the adjustment factor.
It’s important to note that this additional sensor may not measure the process, but the housing for the transmitter itself and be of limited value. On the other hand, multivariable transmitters, such as a Rosemount 3051S MultiVariable flow transmitter:
…have additional sensors within a single transmitter. An additional pressure sensor is located within the transmitter module to measure the line pressure.
These valid process readings can be used as individual values, without need for separate pressure or temperature transmitters on the same line.
With these additional measurements as well as:
…fluid type, primary element configuration and line size to the transmitter, a range of process measurements can be calculated, such as:
- Mass flow
- Volumetric flow
- Energy flow, and
- Totalized flow.
Control systems supporting digital communications protocols such as Foundation fieldbus, HART and WirelessHART can read the multiple process variables from these MultiVariable transmitters. Connor shares another option:
…adding a WirelessHART adapter (or using a native WirelessHART transmitter) is arguably the best interface to get process data, whether simple or multivariable, into an IIoT environment. The adapter… mounts on a transmitter housing and can send data to a WirelessHART gateway without disrupting the established wired connection to the host system. Since WirelessHART is digital, the gateway can convert it to Ethernet or other protocol such as Modbus RTU.
Visit the Rosemount 3051S MultiVariable Flow Transmitter page on Emerson.com for more on the capabilities and specification on this device. You can also connect and interact with other measurement device experts in the Measurement Instrumentation group in the Emerson Exchange 365 community.