Electrician Training Electrical Certification wiring recessed light fixtures Electrical Wiring Electrical Troubleshooting and Electrical Repairs wire outdoor light fixture Home Electrical Wiring Diagrams

wiring home generator and transfer switch wiring a 220 volt range cord outlet Wiring for GFCI Outlets Wiring Outlets and a Switched Outlet Wiring and Installing Ceiling Fans and Remote Controls wire dimmer switch wiring diagrams for switches wiring a dryer cord and 220 outlet circuit breaker panel
Electrical Wire and Cable
ask the electrician
Electrician Training Electrical Certification wiring recessed light fixtures Electrical Wiring Electrical Troubleshooting and Electrical Repairs wire outdoor light fixture Home Electrical Wiring Diagrams
wiring home generator and transfer switch wiring a 220 volt range cord outlet Wiring for GFCI Outlets Wiring Outlets and a Switched Outlet How to Installing and Wire Ceiling Fans and Remote Controls wire dimmer switch wiring diagrams for switches wiring a dryer cord and 220 outlet circuit breaker panel
Electrical Wire and Cable

Electrical Testing for Stray Voltage

digital-meter By
Summary: This article was originally intended for industrial applications but can be a helpful resource when using digital electrical testers for home applications as well as it applies to testing for stray electrical voltage.


Check Out What Others Are Sharing at Ask the Electrician:
Looks like a great resource! I am bookmarking your site. Jim from Santa Rosa, California

How Stray Voltage Affects Multimeter Measurements



Electrical Wiring Video

Basic Home Electrical Wiring by Example

NOTE: A List of All my Helpful Videos

Will Display at the End of This Video

So Keep Watching So I Can Help You Wire it Right!


Check out my YouTube Channel:
» AskTheElectrician «
and Subscribe!



How Stray Voltage Affects Multimeter Measurements
...and What You Can Do About It.
This article was originally intended for industrial applications but can be a helpful resource when using digital electrical testers for home applications as well.

Ghost and Stray Voltage Readings

For most electrical measurements in the industrial environment, a high impedance digital multimeter or electrical tester is the appropriate tool. These test instruments have a relatively high input impedance (>1 megohm), which means that when connected, they don’t load the circuit under test. These test tools generally will not affect circuit operation or circuit measurements when testing for stray electrical voltage.

On the other hand, low impedance test instruments can seriously load down a circuit under test and, in some cases, can adversely affect circuit operation and circuit measurements. This can happen with sensitive control circuits or in many electronic circuits found within industrial machinery.

However, even with a high impedance multimeter, there’s still one confusing measurement situation that can occur in facilities or manufacturing plants. It’s called stray or ghost voltage, and it happens specifically when using a high impedance test instrument for day to day measurements.

Stray or ghost voltages occur from capacitive coupling between energized circuits and non energized, non connected adjacent wiring. Because of this coupling effect and the multimeter’s high impedance, it’s not always possible to determine if the circuit under test is energized or de-energized, and this creates confusion for the person performing the test.


Where are stray voltages encountered?


The most common place to encounter stray voltage is in unused cable runs or electrical wiring in existing conduit. When facilities or buildings are built and wired, it's very common for electricians to pull extra wire through the conduit for future use.

These wires are typically left unconnected until needed, but are subject to capacitive coupling from the powered wires.

Another example is an open ground or neutral on a 120 V branch circuit or in card cages where 120 volt control circuits are used to control assembly line or conveyor functions.

What does stray voltage look like?
Generally, for most electrical measurements, a high impedance multimeter is the best tool, since you don’t want the meter loading the circuit and affecting the circuit measurements. However, when dealing with capacitive coupling, a high impedance meter between ground or neutral to the unconnected cable or open connection will indicate some amount of voltage present. Typically this measured voltage reading may be as high as 50 % of the energized voltage in the same proximity.

Is this voltage real? Yes, it is, but it’s a static voltage, containing no real energy or current flow. When it comes to determining whether a circuit or connection is energized, this stray voltage reading presents a real source of confusion. Is the connection really hot or not?

The Fluke TL225 Stray Voltage Adapter Test Lead Set

Fluke TL225 Stray Voltage Adapter Test Lead SetThe Fluke Stray Voltage Adapter Test Lead Set is an accessory that allows a high impedance multimeter to measure circuits, connections, cables or connectors subject to stray voltages. The adapter provides a low impedance load to the measured circuit, desensitizing the meter to low energy, spurious sources of interference. If the measurement points are energized with a hard voltage, the meter will simply display the voltage reading. If the measurement points contain a stray or ghost voltage, the meter will read very close to zero volts, indicating the circuit or connection is not energized.

Warning
The stray voltage adapter is designed to be used in conjunction with high impedance digital multimeters for measurements on power circuits, to help determine whether the circuit is energized or not. The adapter presents a 3 k load to the circuit under test and thus will dissipate any stray voltage present if the circuit is not energized.

This adapter should not be used on low voltage control circuits or anywhere where the circuit under test could be adversely affected by this low impedance load. The adapter is designed to handle continuously applied power system voltages without damage, however proper use of this adapter is for intermittent use to determine whether a circuit is energized or not.

Sample measurement scenario when testing for stray electrical voltage:

Fluke Sample measurment
The normal reading for an energized 120 volt branch circuit between hot and neutral. This reading is displayed on the meter with or without using the stray voltage adapter.

This is the measurement displayed with the high impedance DMM between neutral and an unconnected wire in the same conduit as a 120 volt branch circuit feed. Note the high impedance meter is displaying 33 volts. This is a capacitively coupled stray voltage reading.

The last reading is displaying the result of the measurement from the previous reading when the stray voltage adapter is placed in the circuit. Note that the reading is now 13 millivolts or very close to zero volts, a non-energized connection.

The low impedance presented by the stray voltage adapter dissipates the stray voltage. If the second reading was a hard voltage, the last reading would have been the same reading as the second reading.

Safety while testing for stray electrical voltage
Testing for stray electrical voltage is a measurement typically made for a short period of time, such as less than a minute. The stray voltage eliminator module contained within the TL225 test lead kit is designed to withstand a continuous application of 1000 volts or less. The module has been tested to meet the IEC 1010-1 second edition CAT IV 600 V/CAT III 1000 V measurement category rating.

On a more personal safety note to keep in mind as your testing for stray electrical voltage:
If you’ve ever doubted your multimeter readings, consider the environment you’re working in. Does it contain the ingredients for capacitive coupling? If it does, and if you need to rely on hot-or-not readings, you may want to consider adapting your multimeter. Stray voltage is confusing at best, and dangerous at worst. Don’t be fooled! Compliments of the Fluke Corporation.

 
Be sure to get your copy of my BIG New eBook:

Complete Guide to Home Electrical Wiring


Wire It Right with the help of my Illustrated Wiring Book
Great for any Home Wiring Project.


See How to Wire it Right!

Learn more about Residential House Wiring
Perfect for Homeowners, Students and Electricians
Includes:
Home Electrical Wiring - Room by Room
120 Volt Circuits
240 Volt Circuits
Multi-Wired Circuits
Wiring Methods for Installing Home Electrical Circuit Wiring
Electrical Codes for Home Electrical Wiring
....and much more.

  electrical wiring  



Electrical Tips to Help You Wire it Right

The Safest Way to Test Electrical Devices and Identify Electric Wires!

The Non-Contact Electrical Tester
This is a testing tool that I have had in my personal electrical tool pouch for years, and is the first test tool I grab to help identify electrical wiring. It is a Non-contact tester that I use to easily Detect Voltage in Cables, Cords, Circuit Breakers, Lighting Fixtures, Switches, Outlets and Wires. Simply insert the end of the tester into an outlet, lamp socket, or hold the end of the tester against the wire you wish to test. Very handy and easy to use.

The Quickest Way to Check for Faulty Electrical Wiring!

The Plug-In Outlet Tester
This is the first tool I grab to troubleshoot a problem with outlet circuit wiring. This popular tester is also used by most inspectors to test for power and check the polarity of circuit wiring.
It detects probable improper wiring conditions in standard 110-125 VAC outlets Provides 6 probable wiring conditions that are quick and easy to read for ultimate efficiency Lights indicate if wiring is correct and indicator light chart is included Tests standard 3-wire outlets UL Listed Light indicates if wiring is incorrect Very handy and easy to use.

Strip Off Wire Insulation without Nicking and Damaging the Electric Wire!

The Wire Stripper and Wire Cutter
My absolute favorite wire stripping tool that I have had in my personal electrical tool pouch for years, and this is the tool I use to safely strip electrical wires.
This handy tool has multiple uses:
The wire gauges are shown on the side of the tool so you know which slot to use for stripping insulation.
The end of the tool can be used to grip and bend wire which is handy for attaching wire onto the screw terminals of switches and outlets..

The wire stripper will work on both solid and stranded wire. This tool is Very Handy and Easy to Use.





RELATED


More about Electrical testers stray voltage

What to do about Stray Electrical Voltage Readings
How to Identify the Source of Stray Voltage: Stray Electrical Voltage Readings Should be Identified and Corrected Right Away - Stray voltage is not normal and may originate from a faulty electrical or electronic component that could potentially become a serious shock hazard and cause damage to equipment.

Sitemap
220 volt circuit questions Why Circuit Breakers Trip Off and What To Do Next Installing 220Volt for a Range and Dryer in a Basement 220 Volt Wiring 220 240 Volt Air Compressor Wiring Electric Water Heater Wiring and Video How to Install a Whole House Humidifier Circuit Converting a 120 Volt Motor to 240 Volts […]

What Are Electrical Testers and How Are They Used?
More detailed information can be found here in this website. Just click the Home Electrical Wiring Testers links....

electrical testers stray voltage - 849