Phantom/ghost voltage
- Thread starter Joey94
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winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
Please give us more info. Describe what you are seeing and how you are measuring it.
Jon
Jon
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
The LoZ setting should be your clue. A high-impedance meter doesn't present enough of a load to pull the voltage down.
I prefer using a solenoid tester unless I need to know the exact voltage, in which case use LoZ or a load should be present.
I prefer using a solenoid tester unless I need to know the exact voltage, in which case use LoZ or a load should be present.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
It is a bit confusing, because normally a digital multimeter will have a high Z input and should show the phantom voltage.
You should think of this as a circuit with extreme voltage drop under load.
In general the issue is that there is some high impedance source of voltage, such as capacitive coupling across the wire insulation or leakage across a switch.
When you measure this with a high impedance meter the voltage is present but if you use a low impedance meter the load of the meter itself is enough to crash the voltage to near zero.
Jon
You should think of this as a circuit with extreme voltage drop under load.
In general the issue is that there is some high impedance source of voltage, such as capacitive coupling across the wire insulation or leakage across a switch.
When you measure this with a high impedance meter the voltage is present but if you use a low impedance meter the load of the meter itself is enough to crash the voltage to near zero.
Jon
Oh, ok.
Use another meter with amp function to check the resistance of the MM 300
Put the DM 300 probes on the voltage, then use another meter to measure the amps going THROUGH THE METER.
From there calculate the resistance..
DrSparks
The Everlasting Know-it-all!
- Location
- Madison, WI, USA
- Occupation
- Master Electrician and General Contractor
You could find a voltage in just about anything, even the ends of your toothbrush with a sensitive enough voltmeter. 
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