This is from Autometers website.
Q. Do I need a sender for my electrical gauge?
Electrical temperature and pressure gauges require the use of a sender matched for the type of gauge in use; the stock sender will only work with the stock gauges. Auto Meter gauges are designed to work with the Auto Meter sender that is included with the gauge. Extra senders are available; check out our Accessories.
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That is the difference, the electrical unit requires a little gizmo that "reads" whatever your gauge is for (Boost, temp, oil pressure) it then converts that information into an electrical signal which is sent to your gauge. Mechanical works exactly as described, you drill a hole into whatever you're trying to read basically, and insert a probe, that probe works mechanically to read pressure, temperature etc. (ever hear of a thermocouple in your furnace or hot water heater, thats a mechanical thermometer basically)
The reason why there are TWO choices is because some people have the know-how and time to locate an appropriate "port" in the system that they want to measure, I.E. Turbo inlet, exhaust downpipe etc. With an electrical unit, you can essentially install the sender wherever you want within the system and run some wires, done.
Last edited by Shadowlightning : 06-12-2007 at 06:35 AM.