Not sure if this helps, but a thermistor for an Airmar transducer should have about 15,000 ohms. Recently, I installed new Raymarine I-70 instruments. I could not get the speedo to work. I tested my transducer and another that a lister gave me. Neither transducer would work because the thermistor in both was bad. We installed a 15K resistor across the circuit. Bingo! We had a speed read out. No sure this is Curtis' problem, but it is food for thought.
Fred Hazzard S/V Fury Portland/La Paz From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Curtis Sent: Tuesday, January 14, 2014 6:50 PM To: cnc-list@cnc-list.com Subject: Re: Stus-List FW: Autohelm St4000 how it should work with the GPS The speed transducer is caput... On Tue, Jan 14, 2014 at 8:22 AM, Rick Brass <rickbr...@earthlink.net> wrote: First post snagged because it was too big. Forgot to delete the string of previous posts. From: Rick Brass [mailto:rickbr...@earthlink.net] Sent: Tuesday, January 14, 2014 8:17 AM To: 'cnc-list@cnc-list.com' Subject: RE: Stus-List Autohelm St4000 how it should work with the GPS Curtis; The elevator version of how the paddlewheel works is that a little magnet causes pulses in the wire, and the instrument converts the frequency of the pulses into speed through the water. I'm not sure that a ohm meter would show me anything even if I knew which pair of pins to test across. As far as water temp goes, there is a thermister in the sensor that changes resistance in response to temperature change, but it would probably only show a very few ohms of resistance and might look like normal continuity unless you have a very sensitive meter. If your wind instrument is not hooked up to a GPS to get Speed Over Ground and heading information, then it uses the speed input from the speed log and the apparent wind information from the masthead sensor to calculate the true wind and the VMG information. There is an inherent error here in that SOG and speed through the water are different due to the impacts of current, but without boat speed information, it isn't possible to know true wind unless you are standing still. Rick Brass From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Curtis Sent: Tuesday, January 14, 2014 7:31 AM To: cnc-list@cnc-list.com Subject: Re: Stus-List Autohelm St4000 how it should work with the GPS I worked with the paddle wheel last night ad was able to clean it. It now spins freely but shows however it still has no activity on the ohms meter. All that being said, how much does this speed help you anyway? I mean it will tell me how fast the river is passing under my boat but not if I'm making speed? The GPS tells me distance over the ground, I have been sailing real good before and not making much distance over the ground. What are your thoughts on this? I will hook it back up and try it tonight after work. But if there is no activity on the meter It may have a bad wire or something. _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com -- At sea, I learned how little a person needs, not how much. - Robin Lee Graham
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