The sending units are mechanical with a pivoting float or a column float. The signal is sent to the gauge based on resistance, but most of the signaling mechanism are not linear. The column type has a magnet on the float that passes by points in the column which changes the resistance signal sent. Some columns have only 4 or 5 position sensors, others have much more. If the column only has 4, the gauge will only register in quarter tank increments. If the column has 8, it will read in eighths. Obviously the more register points, the more accurate the gauge will read regardless if it's a digital or analog gauge. I know the old BX has a pivoting float actuator and an analog gauge. I'm guessing my newer B either has a more sensitive actuator on the pivot arm or they changed to a column type sending unit with eight sensors. I figured someone on here would know. The pivoting arm float types are prone to registering 'full' for a long time since they don't start moving until the level goes from where ever it is above the float down to the bottom of the float. They are also less accurate when the tractor is tilted in the same plane as the pivoting arm. I could not find any info in the owners manual regarding sending unit type for my B. I'm curious enough that I'll check Messick's for a part number and find out.
For what it's worth, I bent the pick up float arm in the BX to move it as high as possible in the tank so it would register sooner, but it still reads full until it's below 3/4 full.
It’s good for telling me when to add fuel, but that’s all it’s good for.
