Hello, my name is Victor, and I'm a Brazilian ichthyologist.
Currently, I'm working on developing a digital ichthyometer, which is essentially an electronic ruler for measuring fish. In this project, I am researching ways to obtain accurate measurements using cost-effective sensors. The desired resolution for the measurements is 1 mm, but I would like to know if it's possible to achieve even greater precision, down to 0.1 mm.
Initially, I considered using laser sensors, but I have also read about linear potentiometers. However, I am still in the early stages of the project and feel a bit lost about how to proceed. I would appreciate any advice or guidance.
Yes, even 1 micrometer is possible. As a crude guide, sensor cost goes up by roughly a factor of ten, for each factor of ten improvement in precision and accuracy.
The more information you provide about how your measurement will be conducted, the more detailed advice you can expect.
Are the requirements meaningful? Even 1 millimeter is too much. How to apply the fishes to the measurement device in the same way to be able to compare them? Pull the fish, straightening it out, X-ray the back bone being straight?..... Even centimeter accuracy is questionable.
What's the actual use of the device?
In the commonly used ichthyometer, the fish is placed on a kind of ruler on top of a plate, with its mouth against a stopper, and we measure the length up to the end of the fin and another up to the last vertebra.
It's all very visual, which is why there's a corresponding error for each person performing the measurement. I believe that with a digital model, this error can be reduced.
I want to keep the idea of placing the fish against a stopper and using a sensor attached to something that moves along with an indication of the exact measurement point so that whoever is operating the equipment can place it at the right spot on the fish, and the length is displayed on a screen.
The attachment and fixation of the fish to the device are done manually.
Basically, the use would be for fish sorting, collecting the sizes to be cataloged in a database that would later be used in other scientific research.
Sorry for any english errors, i'm using chat gpt for translate.
It is difficult to imagine how this measurement process, which involves manual placement of the fish, could be performed with a digital sensor. A camera stand with image processing is a possibility, and 1 mm accuracy is probably achievable.
@Railroader makes the important point that your expectations for accuracy and repeatability may be too high.
How could I make this measurement from the camera? I imagine that the biggest challenge would be measuring from the head to the last vertebra since we usually use touch to identify it.
I'm thinking of a possible solution with lighting from below the fish, where the vertebra is located, making it opaque, and perhaps it would be possible to measure it.
I'd like to take this opportunity to thank you for the help you're providing
I was referring to the digital version of the ichthyometer.
I understand. I think the best way to describe it would be a standardization of measurement and information visualization.
Of course, it's always possible to change the way the material is placed on the device to achieve better results.
Currently, with the standard tool in the market, there is no complex preparation before measurement, and that's exactly what I want to correct. I want to make the data more accurate and simplify the measurement.
Currently, to achieve good accuracy, a significant amount of time is spent manually measuring hundreds of fish from various species. I would say the error is around 5mm for each fish, but it can vary considerably depending on who is measuring.
