GPS Speedometer
08-28-2016, 09:04 AM
#16
Three Wheelin'
Thread Starter
Ok so there seems to be a misunderstanding. Entirely my fault due to my thread leader.
I am not replacing my speedometer with a GPS speedometer BUT rather replacing the pulse generator from the transaxle with a GPS unit that sends pulses to the speedometer. This is an interface sensor that replaces the speed sensor on your rear diff. It interfaces with most cars with electronic speedometers. Obviously, there will be a microprocessor that continuously convert GPS signals into a pulse stream that replicates the output from your mechanical speed sensor, but with GPS accuracy. Reviews indicate that they lag <0.5 secs. This is the technology that the newer cars are using.
I am not replacing my speedometer with a GPS speedometer BUT rather replacing the pulse generator from the transaxle with a GPS unit that sends pulses to the speedometer. This is an interface sensor that replaces the speed sensor on your rear diff. It interfaces with most cars with electronic speedometers. Obviously, there will be a microprocessor that continuously convert GPS signals into a pulse stream that replicates the output from your mechanical speed sensor, but with GPS accuracy. Reviews indicate that they lag <0.5 secs. This is the technology that the newer cars are using.
08-28-2016, 09:37 AM
#17
Rennlist Member
From your description of the problem, it sounds like it is internal to the speedometer, not a signal issue.
So changing WHERE it gets the speed pulse is not going to solve the "jerky" needle movement. I think with a replacement speedometer motor it would be fixed.
Modern cars do use GPS signals IN ADDITION to other signals. It is physically impossible to maintain a GPS signal in a long tunnel for example. If GPS only was used the speedometer would drop to zero once inside a tunnel longer than a few hundred yards. Now, if the GPS signal generator had an AHRS (Attitude/Heading/Reference System) that works similar to an INS (Inertial Navigation System), then it COULD maintain a displayed speed based on the inertia calculations. But now we are talking pretty expensive systems...
So changing WHERE it gets the speed pulse is not going to solve the "jerky" needle movement. I think with a replacement speedometer motor it would be fixed.
Modern cars do use GPS signals IN ADDITION to other signals. It is physically impossible to maintain a GPS signal in a long tunnel for example. If GPS only was used the speedometer would drop to zero once inside a tunnel longer than a few hundred yards. Now, if the GPS signal generator had an AHRS (Attitude/Heading/Reference System) that works similar to an INS (Inertial Navigation System), then it COULD maintain a displayed speed based on the inertia calculations. But now we are talking pretty expensive systems...
08-28-2016, 02:44 PM
#18
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This.