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Hi Wout
Thanks for the information. I will definitely investigate this further, as in addition to the depth problem, I am having problems getting my Laptop to talk to the Autopilot. May be a wiring fault, but apparently the ST60 multi instrument has NMEA In and Out. Back to the depth problem. Have you any idea which display instruments will display a -(minus) sign. Thanks again for starting me off in the right direction Phil "Wout B" wrote in message ... "Phil Stanton" wrote in message ... Does anyone know if there is a depth sounder which shows a negative depth. OK sounds like a loony question. I have a lift keel boat and want to set the offset when there is no water under the keel with the keel down. Same as all sensible people with fixed keel boats. Easy to do with my Raymarine ST60 Tridata echo sounder. Now if I raise the keel to go into shallower waters, there isn't 7 ft (2.2m) of water in a lot of places on the East Coast of England, I still want to know how much water there is underneath me. Hence I need to find an echo sounder that shows 0.0m with no water under the keel when down, an say -0.7m when the depth is 0.7m less than with the keel fully down. Hence my question. I should have thought with the number of lift keel boats there would be a reasonable demand, and lets face it, it isn't rocket science to make a minus sign show up on a LCD display Hi Phil, If that's what you like, it can be done with a Brookhouse NMEA multiplexer. They do much more than NMEA combining/multiplexing alone. Maybe we should rename them "NMEA controllers" or something. One of the functions is NMEA sentence editing "on the fly", i.e. real-time editing of NMEA parameters, as the sentences pass through the multiplexer. Editing directives can be uploaded to the multiplexer in setup mode. http://brookhouseonline.com/pdf%20fi...%20Editing.pdf We have recently added a new editing directive, for making adjustments to fields in NMEA sentences, which is ideal for depth offsets, water-speed correction etc. The *A directive allows you to add or subtract a signed value from any given NMEA parameter field of any specified sentence and if the result is negative, it places a minus-sign in front of it. Of course it re-calculates the sentence-checksum. If you connect a repeater instrument to the multiplexer RS422 output and program it for depth, you'll get exactly what you want, provided you use a repeater that displays the NMEA field exactly as found in the sentence. You won't need a new depthsounder. Your ST60 instrument will be suitable as there is an option for Seatalk to NMEA conversion. Adjust the offset of the ST60 to display actual water depth and set the "correction" in the multiplexer to -7.0 and you will get negative depths on the repeater for any depths under 7 feet. Wout |
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