Oil pressure gauge question

[DWW]

Just wondering why this gauge is supplied directly from battery power and not the stabilised supply, what am | missing here?

[MarekH]

The original senders were of a bimetallic strip type design. The dash 10v regulators were also a bimetallic strip design.

This means a 10v regulator works by passing full voltage and the voltage is regulated down to an average of 10v over time by the bimetallic strip connecting and disconnecting in rapid succession. If you were to connect an LED you'd see it strobing but the only thing normally connected to the 10v are the slow moving gauges.

The oil sender also has the same mechanism inside it but with the addition of an extra contact gap which is dependent on oil pressure so the combined gap controlling the on to off ratio of the sender is the sum of getting it to an average of 10v plus the on to off ratio of whatever the oil pressure is, hence there being no need to externally fix the average voltage that reflects full gauge deflection - it is already self regulating.

kind regards
Marek

[DWW]

Thanks Marek, that answers my question perfectly. I initially thought the sender was also a variable resistive component but now all is clear

[MarekH]

I've seen at least one that was resistive and that'd need a stabilised constant voltage supply. You can tell them apart by putting an LED in series and watching to see whether it strobes under simple battery voltage.

kind regards
Marek