Fishhawk Calibration

[vicarious]

Fishhawk Calibration

Have any Fishhawk owners ever had to calibrate your probes?  

Yesterday, I dropped my X4 probe about two feet below the surface and compared the speed the probe was reporting (at the ball) to the speed being reported at the surface.  Considering the probe was at the same depth as the surface paddle wheel, I expected both the surface and probe speeds to be identical.  Surprisingly, the surface speed was consistently .6 to .9 mph faster than the probe speed.

I repeated the test multiple times, both with and against the current, and the result were consistent.

Thoughts?

 

Thanks,

Brad

 

[rolmops]

It is very easy to do. All the info is in the manual.


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[garrymny]

Yes you have to calibrate it so they read the same, but it must be done in calm water, no wind no current, and I calibrate mine ( surface transducer and probe transducer) to read the same as GPS speed over ground. Again, must be done in dead calm so the GPS isn't jumping all over.

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[Sk8man]

Brad - I'm not sure about the accuracy of the impeller type speed sensors at LOW speed but I know mine always read very high at upper speed on my boat compared with anything and at that range was often up to 10 mph faster at top speed (e.g 56 instead of 46). Could be the case at lower end as well? The other thing is that the resistance of the probe in the water is different than that of the free wheeling impeller and that could account for the difference.

Edited August 1, 2017 by Sk8man

[vicarious]

Thanks Guys!

I reached out to Trevor at FishHawk and this was his response:

"Typically the mechanical surface speed will show faster than your probe speed and SOG due to the fact that the water moving under your hull is accelerating as it travels the length of the boat.  You can opt to calibrate that if you wish, or you can leave it at factory zero. Transducer location plays a role also.

Mechanical speed as we use it is not absolute, but is 100% repeatable. Using your probe speed as a reference point, it doesn't matter if the number is 2.0 or 200 - knowing what the probe speed is at the time of the strike and then duplicating that number is the important thing. "

[Decoy Hound]

"Mechanical speed as we use it is not absolute, but is 100% repeatable. Using your probe speed as a reference point, it doesn't matter if the number is 2.0 or 200 - knowing what the probe speed is at the time of the strike and then duplicating that number is the important thing."

That's exactly right, so when someone asks for a down speed it might be completely different than your down speed. My magic number is 2.6 but someone else might not be calibrated the same to duplicate it.

[IUP30]

I've always just left mine at factory settings.  The only thing that matters to me is down speed and temp and as others have said above, it's only a reference so you can repeat what you were doing.  SOG or GPS speed is right on the fish finder so it's something to give reference to what you're seeing down below with currents and the fish hawk reading. 

[whycanteye]

I check mine at the surface when conditions are calm and compare it to my GPS speed my probe seems to be consistent .4 faster than my sog gps speed so I just factor that in for my down speed, has worked for me.

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[on the lam]

The calibration feature becomes more useful when you want to calibrate your FH to match a different brand speed n temp probe. I calibrated my FH down
.4 to match my Depth Raider.

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