Measuring Resistance with a Digital Multimeter

hello in this video we're going to learn to use a digital multimeter to measure the resistance of us parts of a circuit so in this case I want to measure the resistance of this little bead resistor which is part of this lightbulb circuit and I've got current flowing from the positive end of this battery through the red lead through the resistor through the bulb which is glowing dimly and then back to the negative terminal of the battery and we're going to use this wonderful device which is called a multimeter because it can do many things and we're going to set it up to measure resistance now first of all it's currently set up to measure voltage so that's actually it's not measuring anything we have to change the knob setting to one that says ohms Omega so I'm going to choose a scale that says 200 ohms because I know I happen to know that this resistor is less than 200 ohms if if the resistance is greater than 200 ohms then the meter will just got a blank out like this it says 1 and a blank that means the resistance that it's currently measuring is greater than it can then the scale is set for now the probe leads are connected differently to measure resistance so what we have to do is the black lead stays in the C om or common setting but the red lead has to plug into the socket that says Omega so you look for the Omega symbol and that's where you plug it in if you don't do that you're not going to be measuring ohms now you so right now the meter is measuring blank or infinite and that means that there's not there's no way for the current to get through across the tips of these probes so the resistance between the two probes right now is basically too high or infinite and if I touch the probes together we should get zero ohms so I'm touching them together and I get to ohms well that's because the resistance of the wires themselves and that and the contact leads is about two ohms but that's not bad now to measure the resistance of this little bead resistor I can just take the two ends and can I touch them there and get the resistance and the answer is no I cannot measure the resistance of a live circuit you cannot take an ohm meter which is the digital multimeter measuring ohms you cannot take it to measure resistance of a live working circuit that would be a no-no so what we have to do is just to measure that I'm going to have to disconnect that device from the circuit and if I don't do that then then the voltage and the current that's flowing through it is going to disturb the measurement and it's not going to be accurate so now I've taken the resistor out of the circuit and I can measure the resistance just by holding the probe leads to it and I get a measurement of twenty three point three ohms now remember the bare leads by themselves has about have about two ohms of resistance so you could subtract that out so the resistance of this resistor might be around twenty-one ohms and there's a little color code on the resistor and I am i believe that says it's a 22 ohm resistor so the the meter pretty much agrees with the color coding on the resistor and we've learned set the dial correctly to measure ohms to plug in the wires correctly and to disconnect the device from the circuit in order to measurement to measure it those are the three keys to using an ohm meter time for a quiz true or false you can measure the resistance of a device while it is part of a live circuit that's false you must remove the device from the circuit to measure its resistance you

Channel: MrChanPhysics

Views: 356,282

Rating: 4.7017341 out of 5

Keywords: digital multimeter, multimeter, ohmmeter, electrical resistance, resistance

Id: yEYvlh1KaFs

Length: 4min 22sec (262 seconds)

Published: Wed May 21 2014