2 Making Measurements82 U1461A/U1453A User’s GuideMeasuring ResistanceSet up your tester to measure resistance as shown in Figure 2-16.Table 2-8 Resistance measurement positionLegend Defaul t function Function when is pressedRotary switchposition Primary d isplay Secondary d isplay Primary d isplay Secondary d isplayResistance -Cycles between1 Continuity2 Diode3 Capacitance4 Resistance1 -2 -3 Cable length4 -CAUTION To avoid possible damage to your tester or to the equipment under test,disconnect the circuit power and discharge all high-voltage capacitorsbefore measuring resistance.NOTE Resistance (opposition to the current flow) is measured by sending a smallcurrent out through the test leads to the circuit under test. Because this currentflows through all possible paths between the leads, the resistance readingrepresents the total resistance of all paths between the leads. Resistance ismeasured in ohms (Ω).Keep the following in mind when measuring resistance.– The test leads can add 0.1 Ω to 0.2 Ω of error to resistance measurements. Totest the leads, touch the probe tips together and read the resistance of theleads. To remove lead resistance from the measurement, hold the test leadtips together and press . Now the resistance at the probe tips will besubtracted from all future display readings.– Because the tester’s test current flows through all possible paths between theprobe tips, the measured value of a resistor in a circuit is often different fromthe resistor’s rated value.– The resistance function can produce enough voltage to forward-bias silicondiode or transistor junctions, causing them to conduct. If this is suspected,press to apply a lower current in the next higher range.
