26

I assume, since it has a zero-ohms adjustment at all, that this is an analog multimeter (one with a physical moving needle). In which case, you should try replacing the internal batteries. They are used only in resistance mode (so everything else will work), and if they are weak they will not be able to produce enough current to move the needle to full scale,...


20

Stay away from the 10A terminal. That is for amp measurements ONLY, and creates a dead short between the 10A terminal and the common. This will blow your fuse, burn up your probes, and/or destroy the meter. Never use that unless/until you know exactly what you are doing.


19

Thanks to everyone and particularly to ThreePhaseEel for his suggestion that helped me diagnose the issue. My non-contact voltage detector picks up current within about 18 inches of the fan housing, even while the fan is turned off. The other two bathrooms have the same model fan assembly installed, but the voltage detector doesn't read anything from just ...


12

Keep in mind that using a meter that's not rated for the task can be dangerous! Even with relatively low risk things like residential receptacles. Right off the bat - if you got this meter for free with a purchase of a blue tarp at Horrible Freight, just throw it out. Next, make sure the meter is properly rated for the task. Meters have CAT ratings ...


9

You're not using it correctly. You can only have a single wire running though the clamp - in all the cases you show here you have 2 wires - even the 1st pics with the adapter plugged in to the outlet powering the clip-on LED lamp has 2 wires inside that single round cable. If you use it to measure current from your automotive 12V battery you'll probably be ...


6

Imagine a single, solitary wire. When AC current goes through it, it kicks up a significant Electro-Magnetic Field (EMF). If that field interacts with anything metallic, it can cause all sorts of mischief, not least, it can cause vibration and "eddy current" heating. And this energy isn't free; it adds impedance (practical resistance) to the wire. EMFs ...


6

You say that you put the clamp around a live lamp cord, but for a clamp meter to work, you have to put the clamp around only ONE of the conductors. If you clamp around both wires, you will not get a reading. For most situations, it doesn't matter which single wire you clamp around. They have devices that you can plug in that give you holes to put the ...


5

Likely is a bad switch, or a bad connection. Unlikely is "high resistance wire" And if you are planning to "put your engineering degree to use" please learn the difference in line connected items between "neutral" (Grounded) and "ground" (Grounding - safety ground - whole different thing.) Your safest bet if low on ...


5

As long as the meter's voltage range is initially set to at least the highest that can be there, you won't damage the meter, especially if you make just a momentary initial connection to see what the meter does. What happens with the readings will depend in part on the type of meter, whether it auto-senses polarity, whether it is auto-ranging, and whether ...


5

I have created a line splitter like this with a heavy duty male and female three prong plug and three 14g wires - white, black, and green. 12/2 romex will have a bare copper ground, and I didn't want any exposed wire so I used actual green insulated wire for ground. Use plugs that have an integrated wire clamp so the connections are secure, and don't leave ...


4

Two suggestions: A non-contact voltage tester can detect line-level voltage without needing to complete a circuit. It does this by detecting the alternating electric field that radiates off any “live” household wire. It won’t detect direct current (uncommon in household settings) and will sometimes give false positive readings if the wire being tested isn’t ...


4

Memory key: Because you want to measure voltage (V), use the VΩmA terminal. (Also use that terminal for measuring resistance (Ω) and small currents (mA).) The 10A terminal is special purpose, only for measuring very high current (up to 10 amps).


4

If the outlet safety ground is not really grounded, but is open or perhaps connected to neutral, this could explain what you described. Check the outlet ground to water pipe resistance. This should be low. If the outlet is correctly grounded, then since the compressor case is connected to safety ground ( as the ohmmeter verified), this means your body was ...


3

It sounds as if you want to measure wattage/amps of mains-powered lamps, which are probably powered from an AC source. Unfortunately the meter you mentioned cannot measure AC current; it does DC only. Most (all?) lamps should be labeled as to their wattage. On the old incandescent bulbs it was printed right on the glass. Newer CFL and LED bulbs often have ...


3

I would test the system as follows: Turn of power at the breaker/fuse box Disconnect the two wirenuts going to the wires coming from the wall. Directly connect together those two wires, using a wirenut. Restore power at the breaker/fuse box. If the heater comes on at full power, then the problem must be the thermostat. If the heater doesn't come on or at ...


3

You have 3 basic things to test. 1, the bulb. If you can, put it in a known working fixture. If it doesn't work, it's likely the bulb. 2, the fixture. Put a different bulb in it. If it works it's the bulb, if not, maybe the fixture or upstream. Move the fixture. Does it work now? You could, with care, connect the fixture to a spare wire and plug it into an ...


3

Use the meter and carefully probe in volts mode these two points in the socket. You should read the same voltage as AC mains. Make sure you understand the dangers of probing mains voltage. Also make sure that you are twisting the bulb in the right direction.


3

You're not measuring the amperage, you are measuring the voltage. Set it to measure DC Volts on the 20 scale, read. The maximum voltage for the meter is printed right on it, 600. The device you have is not a transformer, it is a DC power supply. When you connect your lights, measure the voltage again with the lights connected. Don't try to measure the ...


3

1: You have a 3 way switch which has a traveler line. your odds of having a bad 3 way keeping the fixture from not working while possible would mean that both positions [Off and On] of the switch fail, or both switches have failed. Because when one switch is off the other line is working (either of the switches can turn the light on or off.) 2: Measure for ...


3

Code (NEC 300.3) requires that in any given cable, all currents in the cable be equal and opposite. I.E. if you have a 3-wire+ground in your bathroom: red is 3 amps for a fan, black is 1 amp for a light, and white is 4 amps of neutral return for both of them... that is fine. Why?? Because a single wire will throw a great deal of EMF (proportional to its ...


3

Yes of course it reads non-zero in DC current mode with no wire through it. An inductive DC current sensor is measuring an unchanging (more or less) magnetic field. It has no way to differentiate a “real” reading from ambient magnetic fields (from the earth, nearby magnets, hunks of iron, etc). These will vary by location, orientation of the sensor, and ...


3

Resistance may be futile, but persistence is not! :)) The first meter was a dud. After so many unsuccessful attempts to get a proper DC current reading with the first unit I probably didn't even try the REL button on the replacement, being confused by other things. I swear that button did not make the relative mode stick on the 1st one. On the 2nd it does: ...


3

The major sellers of Mastech meters are Amazon, eBay, AliExpress, Konga, Joom, Indiamart and wish.com. That is a huge red flag for cheap counterfeit crud, right off the boat. If that fact did not reflect the price you paid, that's because crud sellers have discovered people are more likely to buy it if it's up-priced comparable to quality units. Also ...


2

The only meter that I know of that could detect leakage from a small hole in insulation would be a megger and it would have to be used by a trained operator not to make things worse. You might try and put the circuit on a GFIC breaker and see if you get a trip from some small voltage leakage. Good luck.


2

You can't measure voltage on a wire. Current travels in loops. Measuring voltage on one wire is like measuring a battery by touching only one end. You know why that can't work, right? Same applies to all power everywhere. Now some people (electronics geeks where Vss=GND; mains electrical guys who are accustomed to a master EGC/GES) tend to think of ...


2

First, make sure you multimeter is set to measuring AC voltage. If your meter has multiple AC voltage range (e.g. 1000, 100V, 10V), use the largest one. Make sure the black lead goes into the "COM" jack and the red lead into the the jack with a letter "V" (or something like "VΩ", but not "A" or "mA"). When measuring, remember voltage is always measured ...


2

Testing the switch in circuit with a continuity tester will show the connected loads. To test it without removing from the circuit the voltage function would be needed with the power on then you would look for 120 across the contacts when the switch is in the off position or in the case of a 3 way the hot will swap from one side to the other. I don't ...


2

Solved! I kept moving further upstream from the GFCI once I detected the open neutral or lower voltage neutral, and I found the culprit receptacle. A working receptacle had clearly burned a bit on one of the neutral wires. I replaced it with a new receptacle and all the downstream voltages were now steady and equal on hot and neutral. The original GFCI ...


2

Power has both a DC and AC component However in human made power, normally only one is created. The other one will give you useless/null redings. Imagine your car has a hatchback with gas door lifts to assist raising the door, and a high mounted center brake light. There are no wires through the door hinges; positive and negative travel through the two ...


2

Loose neutral on either the GFCI, the socket under test, or an intermediate socket.


Only top voted, non community-wiki answers of a minimum length are eligible