The 3 Most basic principles behind hydraulics are:1.) Liquids are incompressible2.) Liquids transmit pressure in all directions and with equal force at right angles to all surfaces3.) Liquids under pressure follow the path of least resistance
Measuring resistance can indicate the health of a component. For example we can determine if an ignition coil is healthy or not by measuring the resistance of its windings. To measure resistance, set your meter to Ω ohms resistance. If you need to select a range, select the smallest range normally 200 ohms. Place the red probe onto one of the small terminals of the ignition coil, and the black one on the remaining small terminal. Your resistance will then display. A normal ignition coil should read about 3.5 to 4 ohms. If your meter reads a much higher resistance it means your ignition coil may have a short and is faulty.
This can be illustrated with this math formula: Force = Pressure x Area.So if we were to push liquid at 1,000 psi into a cylinder with an end area of 2 square inches we would produce 2,000 pounds of force. If we were to enlarge the end area by using a larger diameter hydraulic cylinder with a 4 square inch end area, we would produce 4,000 pounds of force. Since the displacement of the larger cylinder will be greater, our cylinder will move slower but with greater force. Like all other forms of mechanical advantage, we trade speed for power.
A great feature of many DMM’s is the continuity setting. The continuity function measures resistance, and if there is a complete connection the meter will give an audible beep. If there is no continuity your DMM will show “OL” on the display meaning there is an open line. You can use this to test for electrical shorts in wiring or components. I commonly use this function to quickly test for shorted ignition switches and ignition coils.