Showing posts with label 4-20 ma. Show all posts
Showing posts with label 4-20 ma. Show all posts

Tuesday, December 8, 2015

Ethernet I/O Modules Provide Connectivity Advantages

Industrial Ethernet Input and Output Modules on DIN Rail
Industrial Ethernet I/O Modules
Courtesy Acromag
Industrial process control relies on the accurate and timely delivery of process measurements and data to the point of control and decision making. As technology affords more opportunities to measure and transmit process variables, the demand for incorporating the additional information in the control and decision making process expands. The frequency at which data can flow from a process has also increased dramatically, and there is often significant value derived from rapid sampling. Transmitting the voluminous measurement data to the point of control can be accomplished using three basic methods:

  • Point to point wiring from each measurement device to the control point.
  • Wireless linkup from measurement location to controller.
  • Wired network connection between measurement and control devices.
Each of these connection topologies has particular attributes which may better suit a particular application.  For a wired network scheme, Acromag has designed a line of I/O modules that make installation and configuration a smooth operation. Helpful features include:
  • Power wiring options that allow back connected bus power or top mounted screw terminals. You can even provide primary and backup power sources to the two connections.
  • Front facing screw terminals for connections make status checking of inputs a simple operation with your digital volt meter.
  • Modules are rail mounted and can be placed immediately adjacent to one another for high density installation.
  • Modules have a built in webpage for display of operational information. Configuration is accomplished using a front mounted USB port.
  • Operable in temperatures -40 to +70 deg. Celsius.
  • Two Ethernet ports on each unit allow modules to be daisy chained, reducing or negating need for local hubs.
  • Acromag's Priority Channel Technology assures that data update frequencies are maintained, regardless of other network traffic.
The short video below provides additional detail on the useful features of the Acromag line of industrial Ethernet I/O modules. Watch the video. Share your process measurement and control connectivity challenges with a sales engineer specializing in industrial Ethernet I/O. Combine your process knowledge with the state of the art product knowledge of a product specialist for the best solutions.



Tuesday, September 29, 2015

Big Signal Loop? Consider Using a Splitter.

Acromag Industrial Signal Isolated Transmitter
Industrial Signal Transmitters
Courtesy Acromag
Industrial process measurement and control requires the transmission of signals from point to point with no significant distortion. Even with the growing prevalence of wireless signal transmission, over-wire transmission of signals is still a primary means of connecting one device to another.
In the cabled process measurement and control world, the 4 to 20 milliampere signal is generally considered the standard for transmitting analog control and measurement signals over any distance.
There is an immense array of instrumentation and controllers available for use with 4-20 ma signals, so expertise in routing and delivering those signals should be part of your process M&C skill set.

Like just about everything else, routing 4-20 ma signals presents its own set of challenges that require some thought and planning to overcome. Electrical interference is always a concern and must be prevented from impacting the operation of measurement and control devices. Additionally, there must be sufficient power in the signal loop to accommodate the resistance load of connected devices. There are other considerations, but I'm going to focus on these two.

One scenario that can present significant issues is multiple devices requiring connection to the same signal, but with great distance between them. A simple solution can be implemented using an isolated signal splitter.

Features of these units making them an attractive, single box, solution:


  • One 4-20 ma input channel for the measuring or controlling device.
  • The input signal is retransmitted as identical isolated 4-20 ma signals
  • Galvanic isolation from input to output
  • Isolation between channels for safety and increased noise immunity. Fault in one output channel does not impact the operation of the other channels.
  • Reliable operation in industrial environments, with protection from RFI, EMI, ESD, and surges.
  • Low radiated emissions in accordance with CE requirements. 
  • DIN-rail mounting of the unit
  • Plug-in terminal blocks
If you have a very long signal loop, connecting multiple devices, consider breaking the devices into two groups that may allow for a substantially shorter cable length for each group. Connect each group to one of the isolated outputs of the splitter, giving each group of instruments the identical signal without the risks or impractically of an excessively long cable run.

There are other devices available that may combine special characteristics that solve your signal transmission challenges. Contact a product specialist and discuss your existing or anticipated project requirements. I continually urge engineers to take their process expertise, combine it with the extensive product knowledge of a professional sales engineer, and produce the best possible outcome.