Reading/logging data from a display screen using a camera

[wookiehuntr]

Hi, apologies if this topic has been covered somewhere but I'm not even sure exactly what to search for. Here's my situation: I have a couple measurement instruments that display results on a screen but have no provision for computer control or logging. I'd like to be able to use a simple camera whose output is processed in a Labview routine that can recognize various fields on the measurement instrument display screen, do some OCR/etc to parse the image data to numerics or strings and save that data along with time-stamps to output to a file. For instance, I have a basic thermocouple reader that displays temperature that has no computer interface whatsoever. I'd like to monitor and log temperature over some period of time by "reading" the TC reader screen with a camera. 

Has anyone done anything like this before that could point me in the right direction? I am running Labview 2021, do not currently have a camera picked out (that LV needs to be able to receive image/video data from), and do not currently have NI Vision or other installed (although I can, if necessary). Is there an straightforward way to do this using an iPhone for instance?

Thanks in advance,

Jason

[santo_13]

Comparing the engineering cost of developing and debugging such a vision-based solution versus buying instruments that can be automated, the latter will be cheaper and more robust.

For instance, for the thermocouple reader, you can get USB-TC01

[wookiehuntr]

Hi, thanks for the reply. My TC reader example was for illustration only. There are two different instruments I would like to do this with that cost more than $5K. For one of them, even if that was in my budget, there is no available option with any kind of computer interface. I understand that the robustness/fidelity may not be perfect but if I can use a simple USB camera attached to a laptop (that I already have), or an old iPhone (that I already have), I could get a lot more use out of these instruments. So I'm still interested in any other suggestions anyone might have.

Thank you,

Jason

[chupitoelpame]

Hi there. Any luck with this one ? I need this too..

[rolfk]

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@chupitoelpame wrote:

Hi there. Any luck with this one ? I need this too..

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Not very likely. The idea may sound easy and brilliant, the actual execution of it is riddled with trouble. First, cheap webcams are that, cheap! Not useful for any machine vision task really. Second, even more expensive cameras are pretty worthless without the right lighting. And you better make sure that the lighting conditions stay constant. Bright sunlight from a window row across the room, 50m away easily can change your lighting conditions so much that you need to adjust the additional lighting you bought, and which isn't cheap either. Last but not least doing proper image acquisition isn't just clicking together a few analysis functions. And the quality of the used functions is usually directly proportional with the price you are able to invest into it. And IMAQ Vision from National Instruments, while not for free, is by far not the top of the notch in the market anymore for many many years.

So if you intend to make something useful and reliable like this, expect to spend easily 5k for this, and part of that cost are repeat cost for every system. Good image analysis libraries generally also have runtime license costs, that you have to pay for every single installation. Expect to spend a lot more money for the actual initial development, unless you work for free. 🙂

[santo_13]

Edit: Realized late that your instrument has a display and not an analog gauge

There seems to be no off-the-shelf solution but found a few research articles using Google and some YouTube videos too,

https://medium.com/@nayak.abhijeet1/analogue-gauge-reader-using-computer-vision-62fbd6ec84cc

https://www.hindawi.com/journals/mpe/2015/283629/

https://patents.google.com/patent/CN106599897A/en

https://youtu.be/OC0Ar2YrytU

Edit: Found something interesting - http://www.cypressenvirosystems.com/products/wireless-gauge-reader-2/

https://github.com/Aikhjarto/analog_gauge_reader

https://github.com/axn170037/Analogue-Gauge-Reader

Spending more and more time on this seems to uncover a bunch of potential solutions,

https://www.intel.com/content/www/us/en/developer/articles/technical/analog-gauge-reader-using-openc...

https://hackaday.com/2016/04/16/digital-logging-of-analog-instruments/