WIGGY Input Impedance
- Thread starter dereckbc
- Start date
- Status
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Okay, so make up a board with several 120v bulbs in series, and switch in and out the right number for your voltage.dereckbc said:Larry that is true, but a bulb is only good at one specific max voltage, otherwise you have a one time flash bulb
tallgirl
Senior Member
- Location
- Glendale, WI
- Occupation
- Controls Systems firmware engineer
dereckbc said:Larry that is true, but a bulb is only good at one specific max voltage, otherwise you have a one time flash bulb
Get the highest voltage lightbulb you can find. Use it.
bhsrnd
Senior Member
- Location
- Fort Worth, TX
I bought one for my apartment. It's the only lightbulb I'll ever need for the entire place. Of course, a transformer dedicated to it didn't go over well with the management.... We won't even discuss my electric bill.dereckbc said:
RayS
Senior Member
- Location
- Cincinnati
I know the wiggy does draw enough to set off a fire alarm circuit...
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
An article in the latest EC magazine discussed wiggy type testers, and that they have a low input impedance. Those type testers are not Cat III rated and could be dangerous.
I have some pictures from Mike Holt of arc incident that sent a lineman to the hospital (with nomex shirt and rated gloves) due to a flash over from a wiggy.
I should post the pictures and see if anyone knows the background.
I have some pictures from Mike Holt of arc incident that sent a lineman to the hospital (with nomex shirt and rated gloves) due to a flash over from a wiggy.
I should post the pictures and see if anyone knows the background.
tallgirl
Senior Member
- Location
- Glendale, WI
- Occupation
- Controls Systems firmware engineer
bhsrnd said:I bought one for my apartment. It's the only lightbulb I'll ever need for the entire place. Of course, a transformer dedicated to it didn't go over well with the management.... We won't even discuss my electric bill.
My father had some giant monstrosity -- mogul base, several hundred watts -- he'd hang from ridge poles or vaulted ceilings whenever we'd get drug out to a house to cleanup after some crew or other. I have a photo of us kids standing around a stack of sheetrock my mother had turned into a Thanksgiving dinner table the year we built our last house in New Orleans. I'm pretty sure the only light in that photo was from that bulb.
And speaking of wiggys and arcing, the one I was given shows signs it was fried more than once. The electrician who gave it to me was a commercial electrician from up iwire's way.
I have a few thoughts and questions about this.
First, concerning Bob's test results. I think in the past people have quoted 50K as the impedance of analog multimeters, which would be 2.4mA on 120V. Bob's shows much less current. Also, he tested an Ideal tester and not a Wiggy, so it might be different. Does that tester need batteries or would it just be a solenoid like I believe the Wiggy is?
Ideal also calls the Vol-Con a solenoid tester. The basic one doesn't say Cat III, but the Vol-Con XL does. Perhaps the XL isn't really a solenoid tester? You can get a low impedance without a solenoid. Another tester in the same category is the Fluke T3, which is also listed as Cat III. One thing that I noticed on their site is it "Can stay connected much longer than solenoid type testers." What happens if you leave a Wiggy connected to the circuit? How about the Basic Ideal tester Bob tested? How about the basic Vol-Con? The Vol Con XL?
I'm thinking of getting either the Vol-Con XL or the Fluke T3, and not sure which would be better.
Now a different angle. What should be impedance be? Other threads have mentioned to use either an analog meter or a wiggy-type tester instead of a DMM. First, is the over 50K enough load to eliminate phantom voltages? Dereck, does your 50K home-brew work in that regard? I once connected a receptacle tester to a line that was switched off, and it did not make the phantom voltage go away (reduced it though), and in fact was enough to dimly light the LEDs. This would have had a load in a similar range as 50K (the tester does not trip GFCIs).
The Fluke TL225 has been mentioned in other threads as a way to turn your DMM into a low-impedance tester. This says it is 3K. Wording also implies that this can be used to ensure a line is dead before working on it. So it seems a load around 3-5K would reliably remove phantom voltage, but I wonder if this impedance is TOO small to reliably know a line is safe to touch.
As an example, if you could model this phantom voltage like a voltage in series with a resistance, say 120V and 50K. With a 3K load, the voltage measured would be 6.8V (I assume a vol-con would not say voltage). If you say your resistance is 50K when you touch it, you would get 1.2mA which I think you can feel. Maybe these numbers are way off, but how do you know it is safe to touch. The high-impedance DMM is giving the real voltage, you just don't know based on that if it is dangerous.
I'm asking this because I measured a voltage like 80-90 V with my DMM, and not having any other tester I thought I would touch it to confirm it was just phantom. I got a shock. I can't recreate it to see what a vol-con would say. I also have no idea what would give that kind of voltage reading and be dangerous. This was at a switch for a light that didn't work, just taking a quick look (I didn't fix it, so don't know root cause).
First, concerning Bob's test results. I think in the past people have quoted 50K as the impedance of analog multimeters, which would be 2.4mA on 120V. Bob's shows much less current. Also, he tested an Ideal tester and not a Wiggy, so it might be different. Does that tester need batteries or would it just be a solenoid like I believe the Wiggy is?
Ideal also calls the Vol-Con a solenoid tester. The basic one doesn't say Cat III, but the Vol-Con XL does. Perhaps the XL isn't really a solenoid tester? You can get a low impedance without a solenoid. Another tester in the same category is the Fluke T3, which is also listed as Cat III. One thing that I noticed on their site is it "Can stay connected much longer than solenoid type testers." What happens if you leave a Wiggy connected to the circuit? How about the Basic Ideal tester Bob tested? How about the basic Vol-Con? The Vol Con XL?
I'm thinking of getting either the Vol-Con XL or the Fluke T3, and not sure which would be better.
Now a different angle. What should be impedance be? Other threads have mentioned to use either an analog meter or a wiggy-type tester instead of a DMM. First, is the over 50K enough load to eliminate phantom voltages? Dereck, does your 50K home-brew work in that regard? I once connected a receptacle tester to a line that was switched off, and it did not make the phantom voltage go away (reduced it though), and in fact was enough to dimly light the LEDs. This would have had a load in a similar range as 50K (the tester does not trip GFCIs).
The Fluke TL225 has been mentioned in other threads as a way to turn your DMM into a low-impedance tester. This says it is 3K. Wording also implies that this can be used to ensure a line is dead before working on it. So it seems a load around 3-5K would reliably remove phantom voltage, but I wonder if this impedance is TOO small to reliably know a line is safe to touch.
As an example, if you could model this phantom voltage like a voltage in series with a resistance, say 120V and 50K. With a 3K load, the voltage measured would be 6.8V (I assume a vol-con would not say voltage). If you say your resistance is 50K when you touch it, you would get 1.2mA which I think you can feel. Maybe these numbers are way off, but how do you know it is safe to touch. The high-impedance DMM is giving the real voltage, you just don't know based on that if it is dangerous.
I'm asking this because I measured a voltage like 80-90 V with my DMM, and not having any other tester I thought I would touch it to confirm it was just phantom. I got a shock. I can't recreate it to see what a vol-con would say. I also have no idea what would give that kind of voltage reading and be dangerous. This was at a switch for a light that didn't work, just taking a quick look (I didn't fix it, so don't know root cause).
The lower the better, but you run into power dissipation issues with respect to voltage. That is why I chose 50K @ 5-watts. This allows me to measure up to 480 volts without burning up the resistor. I can leave it connected indefinitely without burning up.paul32 said:
If you were to go down to 3K, that device would have to be able safely dissipate about 80-watts @ 480 volts for some period of usable time referred to as duty cycle. That is the reason for the time limitations of the solenoid testers.
Edited note:
With my home brew, it does short out phantom voltages. If you connect it and see 120 volts it is there. It even comes with a touch/fell indicator. If in doubt touch the resistor being careful not to touch the leads. Even at 120 VAC the resistor gets warm to touch 1/3 watt). At 480 you do not even have to touch it, it is warm enough to radiate heat.
Last edited:
For eliminating phantom voltages, I would agree. But for knowing a voltage won't shock you, at some point too low will give a false negative (as I tried to show in my prior post). I don't really know what that point is.dereckbc said:
If a Vol Con says no voltage, could you ever get a shock from touching the same two points? I know if a DMM says close to 0 it is safe.
You have both. Does a T3 eliminate phantom voltages even though it seems to not be low impedance? I don't see that in the feature list on the Fluke site. Is there a reason you have both, and what are the pros/cons of each tester?steved said:
Anyone can chime in. :smile: Thanks.
In case my posts are confusing, there are two issues: I want to get a vol-con or equivalent for troubleshooting, and also want something to know a wire is safe to touch (which is maybe a different tool).
Paul keep in mind I am an engineer, not an electrician. But as an engineer I would think you would need both a Wiggy type device and a DMM. They have different purposes.paul32 said:
Everything revolves around the source impedance. A "Phantom Voltage" is extremly high source impedance around infinity is most cases.
Draw a picture in you mind of a very simple 120 VAC generator (source) with an internal impedance of 200K-ohms. Assume the circuit is open with no load. If you take a DMM and measure the voltage you will read the full voltage of 120VAC (or close to it) because the DMM impedance is around 10M-ohm.
Now connect a Wiggy with an internal impedance of say 3K-ohms. The Wiggy should read 1.77 VAC. Is the circuit safe to work with hot? The answer is yes. The reason is the source impedance.
If you were to take the circuit example above, short out the load, and measured the fault current it would equal .0006 amps (120/200K=.0006). That is the maximum current the source is able to provide at 0-ohms load impedance.
Now you go plug in some figure for a low impedance source like a live working branch circuit. Use realistic source impedance which includes the transformer, breaker, and wiring. 2-ohm?s is a good place to start. Just plug in the three values I used and see what voltages you come out with.
I said "Is there a reason you have both, and what are the pros/cons of each tester?" to steved about having both the VolCon XL and Fluke T3. I was thinking they were similar testers and trying to decide which to get.
Dereck, repeat your calculations with the 50K source impedance. That has a 2.4mA short circuit current, which you could feel. And a wiggy would probably say no voltage.
Without the shock I described above, I would probably figure any 80V type reading on a DMM was phantom and would not shock you.
Dereck, repeat your calculations with the 50K source impedance. That has a 2.4mA short circuit current, which you could feel. And a wiggy would probably say no voltage.
Without the shock I described above, I would probably figure any 80V type reading on a DMM was phantom and would not shock you.
I could ask why 200K? I don't know what the source impedance might be, which is why I was saying if the source impedance is in a certain range a wiggy might indicate no voltage but would be such you could get a shock. Do you know this can't happen?
Another why to approach this: the "standard" method to ensure it is safe is to test the meter on a known live circuit, test the point in question, and test the meter again. OK, does this "standard" say anything about what kind of meter should be used and/or what the meter should indicate to be safe?
Another why to approach this: the "standard" method to ensure it is safe is to test the meter on a known live circuit, test the point in question, and test the meter again. OK, does this "standard" say anything about what kind of meter should be used and/or what the meter should indicate to be safe?
Paul source impedance have everything to do with it, but it is not something you have to figure out because a Phantom Voltage will always be an extremely high impedance near infinity, while a live circuit will always be a low impedance.
A DMM is a very high input impedance device of 10M or more. When connected to a Phantom Voltage it will not load the circuit and read something odd. Just put any meter in AC, and hold one probe in each hand touching the leads, you will see voltage. Stand near a transformer and you could read several hundred volts under the right conditions.
A Wiggy type device or an ole fashion DVM has much lower input impedance, and when connected to a Phantom Voltage will short out the stray voltage because a high source impedance cannot supply current.
Now use some common sense when using Wiggy type devices. If you read something odd like, I don?t know, let?s say 40 volts, something is wrong and caution should be used to locate the source. However if a DMM reads 100 and a Wiggy reads 0, the circuit is safe.
In my opinion a DMM is used to accurately measure a known working good live circuit to check for things like voltage drop. A Wiggy type device is used to determine if the circuit is safe to work on and is dead.
A DMM is a very high input impedance device of 10M or more. When connected to a Phantom Voltage it will not load the circuit and read something odd. Just put any meter in AC, and hold one probe in each hand touching the leads, you will see voltage. Stand near a transformer and you could read several hundred volts under the right conditions.
A Wiggy type device or an ole fashion DVM has much lower input impedance, and when connected to a Phantom Voltage will short out the stray voltage because a high source impedance cannot supply current.
Now use some common sense when using Wiggy type devices. If you read something odd like, I don?t know, let?s say 40 volts, something is wrong and caution should be used to locate the source. However if a DMM reads 100 and a Wiggy reads 0, the circuit is safe.
In my opinion a DMM is used to accurately measure a known working good live circuit to check for things like voltage drop. A Wiggy type device is used to determine if the circuit is safe to work on and is dead.
jcormack
Member
- Location
- Pennsylvania
The use of "Wiggy" type low Imp. voltage testers has been all but "outlawed" in the Mining industry. MSHA has issued several safe-guards against their use. The main reason is shock hazzard when applying the leads - due to the low Imp. of the device it will allow enough current flow to provide a heart-stopping shock if the one of the leads is frayed or mis-handled. Thus the use of devices with High Imp. is encouraged. It only takes 40 ma to stop the heart. As seen in the test above it passed over 50 at 240 - at 480 it could definately be lethal. Its use above 240 is highly frowned upon & in WV mines will get you an IPA (personal fine)
- Status