Custom “Tri-Controller” portable control system for pH, temperature, speed control.
In 1999 a research lab / pilot plant needed to control several parameters in area of their fume hoods with a portable control system that could be easily moved about.
A large beaker filled with the customer’s test solution needed to be heated with an electric mantle wrapped around the vessel, while the solution was being agitated with an over the side mixer and dosed with an acid solution to maintain a pH level. In addition, the heater was to be started up an hour or so prior to the Tech’s arrival in the morning so a timer was incorporated to bring the vessel up to temp at 6:00 am.
All of this equipment was to be in a stainless steel portable enclosure that would not take up a lot of workspace.
We first selected a ¼ din pH control and Timer and a 1/16 din temperature control to read and control the parameters. We then designed an enclosure with a sloping front and hinged cover that measured 18” x 10” x 10” and had a local sheet metal fabricator build 3 of them for the job. Holes were cut to accept the controls and then wired to 120 VAC receptacles that allowed the customer to plug in their 2 heating elements (top and bottom of vessel), their mixer and their acid dosing pump.
Additional receptacles were added to plug in the mixer and the acid dosing pump. A main on off power switch with circuit breaker and terminal strips were installed and the system wired. Quick disconnects were added for the enc pH sensor connection and dual RTD inputs (one for the temperature controller and the other for the pH controller for automatic temperature compensation. We also provided a connector for dual 4-20 milliamp outputs to send the temperature and pH readings to the customer’s recorder.
Wiring schematics and operating instructions were provided. If you are interested to know more about this system and application – read more here.
In 2014 the customer called and asked us to update these “Tri-controllers” and take advantage of more modern instruments on the market today. Instead of 3 portable systems this time, they wanted two portables and one fixed system that could be mounted near the fume hood with the addition of a remote digital display for the pH portion of the system. They requested that we utilize some of the original equipment and modify the functionality of the system as follows:
The two portable systems retained the original pH and temperature controls while the start up timer was removed (no longer necessary) and a ¼ din data logger was added. The data logger records the pH, temperature, mixer motor speed and torque. Necessary quick disconnects were added for all input signals from the various sensor/transmitters and a panel mount USB connector for downloading the data logger records to a thumb drive when desired.
The permanent system was installed in a 14” x 12” x 8” fiberglass raised face enclosure with the same control scheme but with the addition of a remote Precision Digital panel meter that would be visible at the customer’s eye level.
submitted by Wayne Cooke Sr.