A High-Tech Alternative to Paper Chart Recorders
CHESTERLAND OH—October 13, 2011
CAS DataLoggers recently provided the postsale technical solution for a seafood distributor who ordered a Brainchild VR-06 Paperless Chart Recorder to both record and control the temperature in a large oven. The oven was heated by hot water, and the control came from an iris valve. The aim of this controller was to have a thermocouple reading controlling the analog output. The problem with this setup was that the analog output card only worked in a positive direction, and thus it was difficult to have it open the iris valve as the temperature decreased. To resolve this problem, the following steps were taken in programming the Brainchild chart recorder.
The basic layout of the paperless chart recorder was 1 AI183 analog input card and 1 AO183i analog current (4-20mA) output card. The analog input came from a type K thermocouple, and the target temperature range for the oven was between 200°-243°F (93° and 117°C). The analog control needed to have the iris valve fully open at 200°F and fully closed at 243°F.
The analog output could work with values from any available channel in the Brainchild chart recorder. This included measured analog channels as well as virtual math channels. In order to create a channel that would read in the correct direction for the analog output to work correctly, a math channel needed to be used. Using math channel one, the following statement was used: ABS(A1-243). The constant value was, of course, variable in terms of the temperature range desired. This created a range of 0-43 which was then used in the AO settings as the full range of 4-20mA.
In the AO portion of the software, the output was set for 4-20mA, and the ‘Expression’ portion was made as ‘Math1’. The range was then set for 0.0 to 43.0.
The values given were for the specific project that this solution was programmed for, and therefore could easily be changed to suit other projects.
For further information on the VR-06 Paperless Chart Recorder, the VR-18 Paperless Chart Recorder with up to 18 input channels, or to find the ideal solution for your application-specific needs, contact a CAS Data Logger Applications Specialist at (800) 956-4437 or visit the website at www.DataLoggerInc.com.
CAS DataLoggers, Inc.
12628 Chillicothe Road
Chesterland, Ohio 44026