# Tripped breaker pulsing continuity



## GEORGE D (Apr 2, 2009)

I have a situation at a gas station where there are a couple of tripped circuits and one of them pulses meter when checking continuity to ground/neutral. This is not the first time ive seen this and was wondering what might cause that?


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## hardworkingstiff (Jan 22, 2007)

George, I don't understand exactly what you are saying. 

What kind of meter are you using and where are you checking continuity? Also, can you give more detail of the "pulsing"?


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## cowboyznindianz (Mar 4, 2012)

*Pulsing*

I would have to see a meter on it...
I'm not understanding the pulsing
part.....If the voltage is all over the
place, I would tend to follow the neutral....


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## GEORGE D (Apr 2, 2009)

Using a Fluke 289 in ohms-beep mode. The meter just pulses rapidly , beep,beep,beep non stop as if someone is tapping the wire to ground. I measured from line at breaker to ground and neutral at panel. I believe the circuit is most likely feeding a sign but couldn't track down that day. The sign is an led, could a bad driver cause this pulsing perhaps?


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## GEORGE D (Apr 2, 2009)

cowboyznindianz said:


> I would have to see a meter on it...
> I'm not understanding the pulsing
> part.....If the voltage is all over the
> place, I would tend to follow the neutral....


There is no voltage. This circuit trips immediately indicating a direct short circuit. When ohming out it doesn't sound a constant sound, it just pulses fast. I'll be heading back today and was justing curious if anyone ever encountered this.


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## dronai (Apr 11, 2011)

I would disconnect fro the cb, and put a tracer on it. Locate, and disconnect the load. If it's pulsing, it sounds like an electronic issue (driver) I also carry an analog meter to verify readings like this.


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## forgotflying (Mar 2, 2011)

sounds like a line to line short somewhere.
oh lol.......disconnect the load before testing.


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## JRaef (Mar 23, 2009)

Sounds almost like what we used to call a "toe-in-the-water" circuit. Sometimes on SCR based power supplies that are firing into inductors, you pulse one SCR in each phase (I worked only on 3phase) before fully engaging the firing ciruit to ramp up. During the pulses, you look for a rapid rate of rise in current, faster than you would expect, as an indicator that you are about to fire into a short circuit ahead of or inside of the inductor (i.e. a motor or transformer), so you disable the full firing and show a fault. It saves you from having to replace SCRs as often. If your sign has that kind of power supply, or its a rotating sign with a soft starter or DC drive, you might be seeing that test circuit. 

But if it is there, why is it not shutting down the system? Why would it keep repeating? Why would it only be seen with a resistance test? That part doesn't make sense, unless the CONTROL BOARD of the power supply is being fed from a separate power source than the circuit you are looking at that is feeding the SCRs. That would be a very strange circuit design though. Maybe because it is a sign, there is a control / LED power supply, for instance 24VDC, that is separately fed from the rotating motor power? Hard to say without seeing it.


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## hardworkingstiff (Jan 22, 2007)

Maybe the power supply in the sign? If you disconnect the sign from the circuit does it stop? I'm assuming you are correct in that it feeds the sign.


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## GEORGE D (Apr 2, 2009)

hardworkingstiff said:


> Maybe the power supply in the sign? If you disconnect the sign from the circuit does it stop? I'm assuming you are correct in that it feeds the sign.


I will be there shortly, I'm hoping to be able to work on sign from my ladder. It is a building sign (attached to building) and definitely doesn't have moving parts, and its definitely an LED sign. When tracing last time I had to stop due to time and tracing path, it was headed right over tight cashier quarters and didn't won't to mess around back there. Sign is directly on wall behind cashier station. I will definitely keep you all posted on my findings, thanks.


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## wildleg (Apr 12, 2009)

capacitor in the circuit ?

I don't use that meter, but the manual indicates that there is a graphical function to assist you, and that the beeper has more than one function ?


Using the Y Function (Model 289 Only)

W Caution
To avoid damaging the circuit under test, be aware the Meter sources current up to 10 mA at an open 
circuit voltage up to 20 volts.

To measure low resistances with the Meter, position the rotary switch to Y. This function has a 
single range and R is therefore disabled when the Meter is in the Y function.

Only the relative and relative percent functions work with the Y function. Press the softkey 
labeled Menu to access these two functions.

Testing for Continuity
W Caution
To avoid possible damage to the meter or to the equipment under test, disconnect circuit power and 
discharge all high-voltage capacitors before testing continuity.

Continuity is the presence of a complete path for current flow. The continuity function detects 
intermittent opens and shorts lasting as short as 1 ms. The Meter uses three indicators for the 
absence and presence of continuity: a resistance reading, an open/short indicator, and a beeper.

The resistance reading is simply an ohms function measurement. However, for continuity transitions 
that are very short, the slow
measurement response of the Meter will not appear in the digital
display. Therefore, the continuity function uses a graphical indicator for the presence or absence 
of continuity. Figure 16 shows the short and open continuity indication.
Short



Open
est36.eps
Figure 16. Continuity Indicator

To perform a continuity test, position the rotary switch to S and set up the Meter as shown in 
Figure 17. Press the softkey labeled j. In continuity, a short means a measured value less than 8 % 
of full scale for the 500 Ω range and less that 4 % for other resistance ranges.
Note
The Meter operates in manual range only while the
continuity function is selected.


http://www.myflukestore.com/crm_uploads/287_289_umeng0100.pdf
page 31


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## GEORGE D (Apr 2, 2009)

wildleg said:


> capacitor in the circuit ?


Those were my thoughts initially but not quite sure.


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## Big John (May 23, 2010)

How sure are you that there is no AC or DC voltage, induced or otherwise?

I don't recall seeing it with the 289, but I believe it was on the 87V where I have seen continuity pulsing because there was voltage present. I don't think it's a design function, because it wasn't a reliable, steady pulse: I thin it is a side-effect of how the continuity circuit interacts when backfed.


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## GEORGE D (Apr 2, 2009)

Big John said:


> How sure are you that there is no AC or DC voltage, induced or otherwise?
> 
> I don't recall seeing it with the 289, but I believe it was on the 87V where I have seen continuity pulsing because there was voltage present. I don't think it's a design function, because it wasn't a reliable, steady pulse: I thin it is a side-effect of how the continuity circuit interacts when backfed.


Yeah you may be right, I'm sure I checked A/C voltage but should have tried DC as well. I'll be there shortly and hope I nail it down.


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## NacBooster29 (Oct 25, 2010)

My fluke dmm definetely pulses when I have it on continuity and there is voltage present.


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## Jlarson (Jun 28, 2009)

All the flukes do I think or at least all the models I have, the t5 does too.


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## hardworkingstiff (Jan 22, 2007)

GEORGE D said:


> I will be there shortly, I'm hoping to be able to work on sign from my ladder. It is a building sign (attached to building) and definitely doesn't have moving parts, and its definitely an LED sign. When tracing last time I had to stop due to time and tracing path, it was headed right over tight cashier quarters and didn't won't to mess around back there. Sign is directly on wall behind cashier station. I will definitely keep you all posted on my findings, thanks.


I guess there is no disconnect on the sign, and it's hardwired?


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## GEORGE D (Apr 2, 2009)

Ok found problem, the new building signs were never connected and the 'what appeared to be mc going to signs' were actually going to the older signs hidden behind new soffit. From inside it looked like mc was going directly into LED signs. I finally went to roof and luckily found access holes which allowed me to look inside. The other day I had no means of getting into signs or on roof. So as for beeping/tripped breakers, it was the original signs doing that. They look like just old magnetic HO ballasts that had failed or something over time, not sure how long breakers were tripped, possibly each tripped over time as ballasts failed. This was frustrating as I was certain that the mc was going into back of new sign and didn't realize the spacing between inside wall and outside surface, but even then, wouldn't of imagined access holes on top either. Maybe that's typical for gas station structures, idk. Anyhow I ended up having to feed the new signs power, and removed the tripped circuits from breakers. Again thanks for input everyone!


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## Introyble (Jul 10, 2010)

GEORGE D said:


> I have a situation at a gas station where there are a couple of tripped circuits and one of them pulses meter when checking continuity to ground/neutral. This is not the first time ive seen this and was wondering what might cause that?


I see you found the problem already :thumbup:

Help me out with one point of logic. Without complete information you decided to ohm to ground on a circuit that was tripping a breaker. 

Why not remove the conductor from the breaker and test the breaker first? At least you eliminate one of the two instantly. 

Testing to ground to begin with may suggest a short but still doesn't eliminate the breaker. Or does it?


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## GEORGE D (Apr 2, 2009)

Introyble said:


> I see you found the problem already :thumbup:
> 
> Help me out with one point of logic. Without complete information you decided to ohm to ground on a circuit that was tripping a breaker.
> 
> ...


I did that as well but ohming it I got around 1-1.5 ohms on all 3 which puts me pretty close to a dead short, at least I think. I also forgot to mention that it was only 2 of the 3 circuits pulsing, when this panel would be de-energized the pulsing would stop on these circuits which meant that other circuits had something to do with it. I double checked for voltage and found nothing. Honestly I was happy to get signs lit and was ready to call it a day. Any idea what could cause that? I don't know much about magnetic ballasts to know if that's a characteristic of them.


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## GEORGE D (Apr 2, 2009)

I did that as well, even tried other spare breaker but ohming it I got around 1-1.5 ohms on all 3 which puts me pretty close to a dead short, at least I think. I also forgot to mention that it was only 2 of the 3 circuits pulsing, when this panel would be de-energized the pulsing would stop on these circuits which meant that other circuits had something to do with it. I double checked for voltage and found nothing. Honestly I was happy to get signs lit and was ready to call it a day. Any idea what could cause that? I don't know much about magnetic ballasts to know if that's a characteristic of them.


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## Introyble (Jul 10, 2010)

You lost me on the all 3 part im not going to be dishonest. I read back to your OP. Still lost on the all 3 part. I have ADD sometimes, I can't read through the rest when I get stuck on a detail.


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## hardworkingstiff (Jan 22, 2007)

Introyble said:


> You lost me on the all 3 part


Yea, me too. I'm not sure what he means.


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## GEORGE D (Apr 2, 2009)

Introyble said:


> You lost me on the all 3 part im not going to be dishonest. I read back to your OP. Still lost on the all 3 part. I have ADD sometimes, I can't read through the rest when I get stuck on a detail.


No it's my fault, I'm a terrible writer, I scatter things and make it harder to understand. I'll try and clear it up simpler:
I was originally told that the front sign didnt work. I found 3 circuits were tripped in panel. I then started testing ohm/continuity. That's when I discovered the pulsing beep to grnd on 2 of the 3 circuits. With power removed to that panel, the continuity was solid to grnd(no beeping/pulsing) on the wires. Soon as you power up, the beeping/pulsing would start. Hope this sort clears it up some.


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## Introyble (Jul 10, 2010)

Let me ask you this. If we put an ohm meter on the secondary side of a step down and ohm it out (primary open to source obviously) what are we going to expect?

Now lets say we have a branch breaker panel normally fed by that xformer but open to the secondary also. Ohm it out. What do we expect?

I think I had a point, now im getting confused.


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