I'm sure there is a thread on this somewhere, but I can't find it and wanted to follow up with some more info.
The fuel sender supplied with my SLC kit is designed to be used with the Koso gauge. It is a 3-wire sender, requiring voltage input to make its tiny computer brain generate a resistance output that the gauge can read.
As far as I can tell, this should have worked with the Dakota Digital gauge cluster that I decided to go with, as the DD gauge sets are able to sense resistance using a variety of preset curves or a user-definable curve.
The only problem is that the combination didn't work. I also couldn't get a resistance to show up when connecting my electrical meter to the sender.
I emailed with Joel at Centroid, the manufacturer of the sender and he patiently explained something about voltages and resistance that I still don't understand (copied below), but the bottom line is that it wasn't working for me, so I bought an SN35t resistive sender from these guys: Classic Instruments Store / SN35T*. It works great with the DD gauge set, mounts to the existing screw holes on the tank and looks like it should be quite accurate with the user-definable curve that I set by pouring fuel into the tank, 5 gallons at a time.
Lesson learned: Test the fuel sender and gauge combinations BEFORE sealing the firewall, installing the tub, installing the rollbar, installing the ceiling panel and installing the body. Either that or cut an access panel. . .
Email from Joel (who was very responsive, by the way):
"Computerized gauges read resistance by applying a voltage to the sender through a "pullup resistor"-- for example 5 volts through 470 ohms. Then they read the resulting voltage on the Send wire and calculate the resistance that voltage corresponds to. In the example above, 100 ohms from the sender would make 5 x 100/(100+470) = 1.06 volts. Multimeters work the same way, but they use a very low voltage to make the measurement, and any voltage that's in the circuit at the time confuses them."
The fuel sender supplied with my SLC kit is designed to be used with the Koso gauge. It is a 3-wire sender, requiring voltage input to make its tiny computer brain generate a resistance output that the gauge can read.
As far as I can tell, this should have worked with the Dakota Digital gauge cluster that I decided to go with, as the DD gauge sets are able to sense resistance using a variety of preset curves or a user-definable curve.
The only problem is that the combination didn't work. I also couldn't get a resistance to show up when connecting my electrical meter to the sender.
I emailed with Joel at Centroid, the manufacturer of the sender and he patiently explained something about voltages and resistance that I still don't understand (copied below), but the bottom line is that it wasn't working for me, so I bought an SN35t resistive sender from these guys: Classic Instruments Store / SN35T*. It works great with the DD gauge set, mounts to the existing screw holes on the tank and looks like it should be quite accurate with the user-definable curve that I set by pouring fuel into the tank, 5 gallons at a time.
Lesson learned: Test the fuel sender and gauge combinations BEFORE sealing the firewall, installing the tub, installing the rollbar, installing the ceiling panel and installing the body. Either that or cut an access panel. . .
Email from Joel (who was very responsive, by the way):
"Computerized gauges read resistance by applying a voltage to the sender through a "pullup resistor"-- for example 5 volts through 470 ohms. Then they read the resulting voltage on the Send wire and calculate the resistance that voltage corresponds to. In the example above, 100 ohms from the sender would make 5 x 100/(100+470) = 1.06 volts. Multimeters work the same way, but they use a very low voltage to make the measurement, and any voltage that's in the circuit at the time confuses them."
