Adjust STW

D

danderer

Furuno Fan
My newly-installed 525 transducer seems to read a bit low on STW. As an aside, I've never had any transducer on any boat that generated a real good STW value so this wasn't a surprise.

- Is there any way to tweak the STW value from the TZT3 the transducer is connected to?
- Is there a way to have the TZT3 suppress/ignore the STW value?
- Is there any harm to running the system with an erroneous STW?

Configuration: Displacement trawler, TZT3s, SCX20, 711C, DRS4DNXT

Thanks.
 
danderer":5l6fmbio said:
My newly-installed 525 transducer seems to read a bit low on STW. As an aside, I've never had any transducer on any boat that generated a real good STW value so this wasn't a surprise.

- Is there any way to tweak the STW value from the TZT3 the transducer is connected to?
- Is there a way to have the TZT3 suppress/ignore the STW value?
- Is there any harm to running the system with an erroneous STW?

Configuration: Displacement trawler, TZT3s, SCX20, 711C, DRS4DNXT

Thanks.
Click to expand...

There is a calibration setting you can adjust to bring the STW closer to actual. It is under the Initial Settings menu/Calibration. I set mine by doing a quick two way run and noting the SOG from the GPS (or SCX-20) and the STW and averaging to find the difference. Then calculate the percentage error and adjust the calibration setting.

I am not sure what you mean by "suppress" the STW value. You have a choice in the data boxes and elsewhere to select SOG from the SCX-20 as the displayed speed and don't need to look at the STW at all. In my case, I have the STW and SOG displayed on the fishfinder page because the STW is good to know when trolling. Otherwise on a planing hull boat it isn't especially useful.

The other thing you might want to use is the 3 axis speed from the SCX-20, which will show you set and drift introduced by currents. With a displacement speed boat, that will be quite useful information.
 
Thanks much. I'll look for that option.

"Suppress" as in just not making the data available, either on the net tor even to the TZT3 that is generating it. I don't know what devices might be looking for STW (the AP maybe?) and so if I know the number is unreliable I was thinking to just suppress/hide it.
 
Is your STW coming from an Airmar "Smart Sensor" and going straight on to the NMEA 2000 network? Short of introducing another interface to filter it, I doubt you can just get rid of it. I don't think there is any way to reprogram a DST800 to stop it from transmitting STW data. I don't think that there is anything on your network that actually uses the STW data, however. It is just available to display. The autopilot will use the SOG data from a GPS or satellite compass to adjust steering parameters (for a planing hull) as will the radar for its ARPA target tracking and collision avoidance alarms.

If you don't want to see the STW data anywhere, just customize the databoxes any place you see STW to change to SOG or another sort of data you do want to see. You can do the same on the 711C autopilot control head if you have one of those.
 
Not really a matter of display but rather something that might be using the data in preference to the (more accurate) SOG.

Found the Calibration section on the TZT3. Any more obvious and it would have smacked me. Thanks.
 
I have the airmar DST810 installed on my boat. Straight out of the box it seemed to be pretty close to matching my GPS speed +/- current. Everything that needs a speed input is set to the SCX20 for that data. The STW for me is only for my rockfish trolling. Any other time I don't even look at it.
 
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