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[TG11] Analogue Wind Display instability with rotation sensor
11-01-19, 07:51 PM (This post was last modified: 11-07-19 03:27 PM by Chuck - Raymarine - Moderator.)
Post: #1
[TG11] Analogue Wind Display instability with rotation sensor
Dear Raymarine,

my Micronet analogue wind display (T112) flips the wind direction needle 180 degrees frequently, but only when the apparent wind is ahead of the beam. It does so on either tack. This creates havoc with the autopilot in wind vane mode.

My system includes:
T120 wind transmitter (2011 vintage)
T112 analogue wind display (new)
T111 dual digital display (new)
T030 entry-level single digital display (2011 vintage)
T221 mast rotation sensor (new)
T121 hull transmitter (new)
Compass Hull transducer (CHT) (new)
T122 wireless transmitter (new)
(connected to T122) Actisense NMEA 0183 to NMEA 2000 converter with SeatalkNG adapter (new)
EV-1 solid state gyro (new)
AC-100 autopilot actuator with tiller pilot drive (new)
p70s autopilot control head (new)

The only potential solutions I can think of are:
-reverse CHT 180 degrees and recalibrate.
-renew T120 (expensive, I'd rather not have to do that, especially as I've just replaced the anemometer bearing)

Is it possible that the T112 is flipping between boat heading inputs (between the CHT input and the EV-1 input), possibly because one of them is dropping in and out?

Solutions or at least suggestions would be very welcome. More detail on my setup saga is available in the thread "Rotating mast, Tacktick wireless and EV-100" in the "Autopilots" forum.

Regards,
Nick
F-32 "Amazon"
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11-07-19, 06:46 PM
Post: #2
RE: [TG11] Analogue Wind Display instability with rotation sensor
Hello Nick,

Is it apparent wind that you're looking at, or true?
When the problem occurs, what happens with the wind angle afterwards? Still indicates a shifting wind angle but inverted, or static wind angle, or something else?

The mast rotation calculations will only use heading data from the fluxgate connected to the Hull Transmitter, not the EV, so I don't expect that the system is toggling between these two heading sources. What I think is more likely is either that:
  • you are looking at True wind and your speed-through-water paddlewheel is sticking occasionally, which will of course corrupt the results of the TWA calculation
  • you have a broken winding in your fluxgate compass which is occasionally giving incorrect heading data into the mast rotation calculations.

Next time the problem occurs, I would suggest:
  • unplugging the link between STNG and the Wireless system, just as a precaution (this is also needed for the next step)
  • checking what heading data is displayed on the Wireless system - is this broadly accurate, is it static, does it change smoothly and evenly as the vessel turns?
  • checking your STW data: is this accurate and changing, not static or zero?

Regards,
Tom

Raymarine since 1999.
Interests: Diagnosis of problems in sonar/fishfinders, NMEA2000, ethernet comms, autopilots, thermal cameras
Location: Sydney, Australia.

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11-11-19, 01:50 AM
Post: #3
RE: [TG11] Analogue Wind Display instability with rotation sensor
Hi Tom,

Thanks for your assistance.

I think that all of my observations pertain to apparent wind direction. In addition, I don't tend to insert the speed/ depth hull instrument into its tube for day trips, as the tube has lost its valve and lets an undue amount of water into the bilge when the instrument is inserted or removed. I rarely choose to use a true wind display. There is a possibility that I have switched my wind display into true wind mode and not noticed - in the absence of a STW input, would this make the wind direction reverse?

The mast rotation calculations can use the data from the EV unit - just yesterday, I disconnected the CHT to see if this had an impact on the problem, and, while the calculations were clearly still working using the EV data via the T122, it did not stop the intermittent flipping of the needle. The original deviation calibration was not carried out with the EV (as far as I can tell so far, it is impossible to calibrate deviation with the EV input).

I am intrigued by your suggestion regarding the MRS fluxgate, but I note that the needle, when it flips to the wrong direction, always appears to flip exactly 180 degrees, and can still be used by the helmsperson in inverted mode. The mast rotation calculations still seem to work, just with a 180 degree error in the output. When it flips back to the correct orientation, it also flips exactly 180 degrees. Correct me if I'm wrong, but if the MRS fluxgate had an intermittent open circuit, wouldn't the rotation calculations completely fail at that point?

I will follow your advice and trial a disconnection of the STNG from the Micronet to see if the Micronet-only system functions as it should.

Regards,
Nick.
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Yesterday, 10:10 PM
Post: #4
RE: [TG11] Analogue Wind Display instability with rotation sensor
Hi Nick,

Quote:The mast rotation calculations can use the data from the EV unit - just yesterday, I disconnected the CHT to see if this had an impact on the problem, and, while the calculations were clearly still working using the EV data via the T122[/quote
The information that I had been given was that Mast Rotation would only work with compass data from a Hull Transmitter, not EV heading through a Microtalk, but the colleague who gave me that information has left the company and I don't have the time to test if for myself. If it's working for you, very good. The EV's heading data will be much better than any fluxgate.

[quote]There is a possibility that I have switched my wind display into true wind mode and not noticed - in the absence of a STW input, would this make the wind direction reverse?
STW missing completely would prevent the calculation of True Wind, but incorrect STW will give incorrect TW. In certain circumstances (e.g. motoring downwind) STW reading zero will give inverted TWA, but not in all circumstances. It's just something we need to eliminate.

Quote:if the MRS fluxgate had an intermittent open circuit, wouldn't the rotation calculations completely fail at that point?
I've never tested an MRS with failed flxugate, but failed pilot fluxgates can give a heading which toggles between a correct and incorrect value depending on whether you're within or outside the 'dead sector' that's a typical symptom of this kind of failure. It wouldn't give exactly the symptoms you describe but I am always careful of interpreting symptoms over-literally, we see a lot of apophenia in the problems reported to us.

Unless there is a good reason otherwise, I would always advise only having a single source of heading in your system and the EV will give far better heading data than the fluxgate. If you were going to disconnect something, the one I would disconnect would be the fluxgate from the hull transmitter rather than the EV.

Regards,
Tom

Raymarine since 1999.
Interests: Diagnosis of problems in sonar/fishfinders, NMEA2000, ethernet comms, autopilots, thermal cameras
Location: Sydney, Australia.

Please don't PM me asking for direct support, please ask a public question instead so that others can see the question and answer. Forum posts will always be answered before PM requests.
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