Title is the question.

I'm using a Klein NCVT- 3 Voltage tester with a bar graph indicating voltage, and don't see anything in the instructions, and haven't ran across anything in a textbook or internet on this.

Voltage tester is testing at 2 out of 5 bars, still yellow, not red.

Voltage meter indicates <2 Volts.

2 Answers 2



A non-contact tester is used to double-check that a circuit is on/wired correctly (i.e., if it doesn't light up when expected, then there is a problem) or off (i.e., if it lights up when you don't not expected, then there is a problem). When used to check that a circuit is off, that is typically to make sure that it is safe to work on the wiring:

  • Check circuit is on (using tester or by checking that light or appliance is on)
  • Turn off breaker or remove fuse that you think controls the circuit
  • Check circuit is off (using tester)

Remember, it takes a tiny fraction of an Ampere (GFCIs are rated in milliamps) at 120V to kill. SAFETY FIRST.

All that being said, there can be phantom voltage from another circuit or there could be low voltage (telephone, network, doorbell, thermostat) - neither of which would be a problem.

The ground wire ("exposed copper wire") under normal circumstances will carry no current at all except when there is a fault in a circuit. There are limited circumstances (certain types of switches) where a very small amount of current is allowed on the ground wire. However, there are a number of other incorrectly wired situations that could cause dangerous current on the ground wire without any obvious fault, including:

  • Ground used instead of neutral - e.g., need two hots + neutral + ground, only have hot + neutral + ground, improperly used neutral wire as a hot and ground wire as neutral
  • Neutral and ground connected together where they shouldn't be, allowing all neutral current to flow on both neutral and ground
  • Wires simply connected to the wrong places and "happen to work", but quite dangerous.

The only way to tell for sure is to check the voltage with a multimeter. The finger test is NOT RECOMMENDED.

  • Thank you. Voltage meter indicates >2 volts.
    – user289394
    Jul 17, 2019 at 21:54
  • 1
    What do you mean by ">2 volts"? 3 > 2 and is no problem. 240 > 2 and is a big problem. Jul 17, 2019 at 22:07
  • <2*... meant less than. how many volts would be harmful? likely it would be either fairly immaterial or 120?
    – user289394
    Jul 17, 2019 at 22:46
  • 2
    To some degree, the current matters too. But as a general rule, voltage < 50V means network, telephone, doorbell, thermostat, etc. or is phantom voltage induced on a 120V or 240V wire. But a 12V car battery can give you quite a shock too... Jul 17, 2019 at 22:59

Safe to touch the insulation (that is undamaged)...

But NOT the conductor under any circumstances.

But for me, and this is IMHO, give me my favorite Fluke multimeter over that device as when I need to check for a loss of voltage ie 10% or 20% low etc it's the tool for the job.

  • thank you. for good measure, the conductor is the exposed copper wire.
    – user289394
    Jul 17, 2019 at 18:51

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