I want to get data from an stand-alone DMM (multimeter) into a log file. There is no direct interface, so I need to take a still image of the reading on the LCD and convert it into a text string. For example, given the image below, I want to write "3.539" into a file, and do this repeatedly every 10 seconds or so.
- image of multimeter display
- Fluke-DMM.JPG (41.21 KiB) Viewed 19611 times
Apart from getting good enough still frames from a camera, this is basically an OCR (optical character recognition) problem. I gather there is a very powerful, open-source OCR program called
Tesseract which is available for Ubuntu, but I'm not sure if anyone has successfully run this on a R-Pi (?) Apparently Tesseract can read entire books, but for this application, I only need to detect digits 0-9 which are each in a fixed location in the frame, so maybe there is a simpler option.
(Note, I know there are DMMs with built-in serial / GPIB / USB ports, and I have some of them, but in this case I want more isolation between the computer and the meter than most of them provide. Also, in one meter I'd like to debug what seems to be an occasional error in the GPIB output.)
I occurs to me that one problem here which you don't have with a book, is the case where the frame is taken with the meter just changing from one reading to another, when the digits may be superimposed. So maybe I also need a "change detection" image algorithm that only presents an image to the OCR which has not changed for the past few frames.
