Re: proper ohm meter for testing electrical components on '73 johnson 135
I'll give it a try. Used to be, before digital readout meter hit the market, that VOMs (Volt Ohm Meters) would load a circuit you would be trying to read. That load was usually in the 5 to 50 thousand ohms/volt resistance values depending on the manufacturer. The higher that ohm/volt number, the less it would load the circuit. In other words if you were trying to read a voltage, the meter itself would use some of the voltage as it was reading the voltage. And therefore you wouldn't get the exact voltage reading but a lower reading value because of the additional load on the circuit. Example would be reading a battery voltage the really was 12.6 volts but the meter would read maybe 11.9 volts because of the ohm/volt loading factor. Well they figure out a way to allow high resistance meter readings and lower resistant meter reading by circuit design. Hence a hi/lo switch. And there are times you want such options. Loading a circuit can show you if there is enough current capability to work properly. So you would use a high loading factor (lower resistance value) to purposely load a circuit. And the flip side was to get as high a ohm/volt circuit to get a more actuate voltage reading. I know this seem overwhelming. So understand that new DVMs (Digital Volt Meters) are so high in the input resistance values that they virtually don't load a circuit very much if at all. So what you read is basically the true value. Another way to look at it is like this. If you have two wires and they are not touching , the resistance between them is so high that it becomes infinity or totally open. And conversely if you touch those wires together, the load become near zero ohms which is a short and loads the circuit to the extremes... The manual you are talking about uses the old type meters and there are time you want to load the circuit, hence the lo setting, and time you don't want to load the circuit hence the high reading. Hope that makes sense and didn't overly confuse you... A lot to grasp and understand without getting into electronics too deep...
