The WebTransmitter has been developed to copy data from the WEB seamlessly into a control system as a 4-20mA signal. Once in the control system, the data can be either merely displayed on the Human Machine Interface (HMI) or used in logic as a Process Variable (PV).

This system has been developed to provide the Alberta Electric System Operator (AESO) System Marginal Price (SMP) to facility operators due to the high volatility of the electricity price.

The original systems included a pc computer with custom software and an ethernet enabled logic solver. With advancements in ethernet enabled Single Board Computers (SBCs), a simple but powerful system has been developed to do this with a single device - the WebTransmitter!


The WebTransmitter has the following features:

  • Input power can vary from 15Vdc to 30Vdc
  • Two (2) isolated 4-20mA loops
  • One set of 5A 30V dry contacts that, by default, close each time the Internet is queried to monitor the health of the system
  • Remote reset capablity
  • Optional external LCD display to provide status information
  • WEB configurabile settings
These features make the WebTransmitter a powerful tool to monitor energy prices and provide information so that one can optimize the facility for cost effective operations.


Included is a short list of related sites that relate to the WebTransmitter:


Version History

Version 1.R - May 16, 2021
  • Minor update - add option to read parse AIL from CSV instead of HTTP.
Version 1.Q - April 14, 2021
  • Minor update - add error check to HTTP read of AIL.
Version 1.P - September 18, 2019
  • Minor update - add terminal functionality to display configuration.
Version 1.O - September 16, 2019
  • Minor update - display CRC for existing and new config.
  • Minor update - ensure error value set in default parameters.
Version 1.N - January 14, 2019
  • Provide feature to allow for adjusting the zero in the zero and span of each of the two ports.
Version 1.M - January 11, 2019
  • Added option to poll the Alberta Internal Load (AIL).
  • Implement device to check multiple times for config file.
  • Revert to using battery backed up configuration rather than reseting the configuration to force a new upload.
Version 1.L - April 4, 2016
  • Add 0.5 to DAC converstion to ensure proper rounding.
  • Implement data type "4" to read actual SMP; data type "1" is hour ending SMP.
  • Correct minor bug to prevent string overrun when calibrating.
Version 1.K - April 4, 2016
  • Provide support for both linear (existing) and logorithmic outputs. This allows better resolution at lower SMP prices.
Version 1.J - April 2, 2016
  • Allow terminal session to force output from 0mA to 20mA for testing and calibrating.
Version 1.H - December 28, 2015
  • Update DB9 to support commands via terminal session.
Version 1.G - December 28, 2015
  • Configure DB9 to support a terminal session.
  • DB9 serial connection requires hardware revision 1.2 or greater.
Version 1.F - March 12, 2015
  • Update display output to support a terminal session.
Version 1.E - May 13, 2013
  • Utilized revised NGX WEB site.
  • Corrected bug in runtime display.
Version 1.D - June 22, 2011
  • Add feature to write status info to WebTransmitter DB.
Version 1.C - June 9, 2011
  • Update to ensure that System Update time is correct.
Version 1.B - June 6, 2011
  • Ensure that the system clock is updated with each http request.
Version 1.A - June 5, 2011
  • Complete rewrite using new http client libraries.