Fish-Finder Factory Calibration Story

[hetek]

Hi All -

Thought I'd share a "Marine Electronics" story from my past...

Back in the early '80s I worked at a marine electronics company in NJ. My career path there led me through "Final Test and Calibration Technician". We sold the "spinner" type fish-finders back then.

One of my tasks was to calibrate the depth settings on the fish-finders. In order to do this I had to place the transducer in a fixture which then lowered it into a tank of water, but rather than being in the vertical position, it was in the horizontal. You see, the tank looked like a 2' x 2' x 10' fiberglass and plywood coffin filled with water.

The transducer pulse didn't mind which direction it traveled and as long as I set the display for 10' it was calibrated. (It was a little more involved than that, but that's the basics of it).

The water in the tank was stagnant and it got a bit funky over time and it needed to be filtered periodically. We had a portable pool filter that I would wheel over, put the intake and discharge hoses into the tank and let her run.

One day I left the filter running while I went to lunch. When I came back, I found that while I was away, the discharge hose had hopped out of the tank and was emptying the contents of the H2O coffin onto the factory floor!

Math time: 2'x2'x10'=40 cubic feet... ...or just under 300 gallons!

I learned how to use a mop that day but we had the cleanest floor in all the factory.

"Updated Filtering Procedure: 1. Firmly secure both intake and discharge hoses to tank... "

[RobS]

If the tank was 2x2x10, you should have been setting the display for 2', not 10'. No wonder they make this stuff over seas now! The standard is LxWxH, right?

Sounds like the common washing machine hose dislodge and overflow flood claims we get time to time..

[hetek]

OK, Rob, I stand corrected...

"L x W x H" makes it 10' x 2' x 2'. Still just shy of 300 gallons.

The trick to calibration was not to set the primary return at 10', but to crank up the gain and set the 9th reflection at 100'. Being the spinner-type finder you'd see a blip at each 10' increment on the display.

Speaking of "being made overseas" now, apparently it is so. Aqua Meter Instruments is no longer there. Doubt if they're even in business anymore. Google maps shows my old factory as a climate controlled mini-storage business now. The compass division was sold off to Rule Industries years ago.

Funny side note: With each unit I had to fill out that piece of paper that said "Inspected By..." with some calibration details and my initials. About 4 years later I was working as a new boat rigger at Ulrich Marine in Southold, NY (now Southold Marine Center). I'm installing an Aqua Meter fish-finder and there's that piece of paper with "JFB" on it.

Wonder who that could be.