L
Louie
Guest
can someone tell me how to test/measure an inductor on a power supply
circuit board. can it be done in circuit with a VOM?
TIA
louie
circuit board. can it be done in circuit with a VOM?
TIA
louie
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D
Dean
Guest
You could simply test it for continuity with the resistance function of your
VOM just to see if its blown. You can get special meters - usually called
LCR ( inductance capacitance resistance ) meters that will measure
inductance in micro and milli Henries or Henrys or whatever they measure it
in these days. Or if you're smart you could test it in a circut with known
frequency and amplitude and see what effect it has then calculate it. Or you
could replace it for a few bucks and at worst finish up with a spare
inductor to put in a tin and forget about.
Dean.
"Louie" <beavisnbutthead@softhome.net> wrote in message
news:xvE_a.96191$Vt6.31811@rwcrnsc52.ops.asp.att.net...
VOM just to see if its blown. You can get special meters - usually called
LCR ( inductance capacitance resistance ) meters that will measure
inductance in micro and milli Henries or Henrys or whatever they measure it
in these days. Or if you're smart you could test it in a circut with known
frequency and amplitude and see what effect it has then calculate it. Or you
could replace it for a few bucks and at worst finish up with a spare
inductor to put in a tin and forget about.
Dean.
"Louie" <beavisnbutthead@softhome.net> wrote in message
news:xvE_a.96191$Vt6.31811@rwcrnsc52.ops.asp.att.net...
can someone tell me how to test/measure an inductor on a power supply
circuit board. can it be done in circuit with a VOM?
TIA
louie
J
John Crighton
Guest
On Thu, 14 Aug 2003 04:47:25 GMT, Louie <beavisnbutthead@softhome.net>
wrote:
inductors for large power supplies interest me also.
I had a little play around with them for use in a home
built DC welder. I was using the cores from discarded
microwave oven transformers. When there is a gap
in the core, to prevent the core from saturating when
direct current flows through it , I think the correct
terminology is "choke" rather than inductor.
Anyway, thanks to Phil Allison, he put me straight
on adjusting the gaps in my chokes.
Here is what I did in my situation.
variac--->welder---->choke --->100A shunt--->back to welder
The Variac initially is turned down to near zero output.
The choke is in series with the shunt across the welder terminals.
I used an oscilloscope to look at the sine wave shape
across the shunt. Phil pointed out that when it starts to distort
that is the onset of core saturation.
So I backed off the current using the variac.
Measured the Peak to Peak voltage across the shunt
(divide by 2.82) and calculated the current.
Also used a digital voltmeter as a double check.
Now I knew the maximum current I could put through
the choke before the core saturated.
By trial and error I increased the gap so that the core
did not saturate at 100 amps. Now the downside is,
as the gap is increased the inductance decreases.
I used a little Marconi inductance bridge to measure
the inductance at various gap settings.
About 0.1 milli Henries with my gap set to suit 100 amps.
I was aiming for 1mH. My core was far too small.
I came up with this 1mH figure by messing about with
a computer program called Electronic Workbench.
You can alter values of components and check what
the ripple voltage on the output of your simple choke
input filter will be like for various load currents. I learned
a lot from this, for example, the ripple voltage is maximum
when no current flows, so you have to determine a
minimum current flow from your supply to keep the ripple
voltage down to an acceptable amount.
From my trial and error testing, my choke at 0.1mH
was just not big enough for the job.
Louie, that is about as much as I can help you
with your inductor problem. If you tell us what
you are building or repairing then maybe Phil
or some other members of the gang will chip in
with some suggestions.
Regards,
John Crighton
Hornsby
wrote:
Hello Louie,can someone tell me how to test/measure an inductor on a power supply
circuit board. can it be done in circuit with a VOM?
TIA
louie
inductors for large power supplies interest me also.
I had a little play around with them for use in a home
built DC welder. I was using the cores from discarded
microwave oven transformers. When there is a gap
in the core, to prevent the core from saturating when
direct current flows through it , I think the correct
terminology is "choke" rather than inductor.
Anyway, thanks to Phil Allison, he put me straight
on adjusting the gaps in my chokes.
Here is what I did in my situation.
variac--->welder---->choke --->100A shunt--->back to welder
The Variac initially is turned down to near zero output.
The choke is in series with the shunt across the welder terminals.
I used an oscilloscope to look at the sine wave shape
across the shunt. Phil pointed out that when it starts to distort
that is the onset of core saturation.
So I backed off the current using the variac.
Measured the Peak to Peak voltage across the shunt
(divide by 2.82) and calculated the current.
Also used a digital voltmeter as a double check.
Now I knew the maximum current I could put through
the choke before the core saturated.
By trial and error I increased the gap so that the core
did not saturate at 100 amps. Now the downside is,
as the gap is increased the inductance decreases.
I used a little Marconi inductance bridge to measure
the inductance at various gap settings.
About 0.1 milli Henries with my gap set to suit 100 amps.
I was aiming for 1mH. My core was far too small.
I came up with this 1mH figure by messing about with
a computer program called Electronic Workbench.
You can alter values of components and check what
the ripple voltage on the output of your simple choke
input filter will be like for various load currents. I learned
a lot from this, for example, the ripple voltage is maximum
when no current flows, so you have to determine a
minimum current flow from your supply to keep the ripple
voltage down to an acceptable amount.
From my trial and error testing, my choke at 0.1mH
was just not big enough for the job.
Louie, that is about as much as I can help you
with your inductor problem. If you tell us what
you are building or repairing then maybe Phil
or some other members of the gang will chip in
with some suggestions.
Regards,
John Crighton
Hornsby
M
Malcolm Faed
Guest
Here is an almost free LCR meter, if you already have a PC with a sound
card.
http://www.i-adrian.home.ro/ (follow the Multimeter link)
Here are the results of some tests I did.
=====================================
Sound Card LCR Meter Comparison
R = 99.1
Resistance
DSE DMM MM.03 % Difference
47.2 47.7 1% M2
460 465 1% M2
1000 1010 1% M2
1522 1536 1% M3
2950 2991 1% M2
4710 4782 2% M2
10200 10410 2% M2
33000 33900 3% M2
100300 95000 -5% M2
Capacitance
Cap M MM.03
0.0038 0.004 5% M1
0.00973 0.01 3% M1
0.023 0.021 -9% M1
0.92 0.93 1% M1
1.007 1.01 0% M1
2.021 2.06 2% M1
22 21 -5% M1
48 46.2 -4% M1
103 101 -2% M1
322 378 17% M1
978 2230 128% M1
Regards,
Malc.
"Louie" <beavisnbutthead@softhome.net> wrote in message
news:xvE_a.96191$Vt6.31811@rwcrnsc52.ops.asp.att.net...
card.
http://www.i-adrian.home.ro/ (follow the Multimeter link)
Here are the results of some tests I did.
=====================================
Sound Card LCR Meter Comparison
R = 99.1
Resistance
DSE DMM MM.03 % Difference
47.2 47.7 1% M2
460 465 1% M2
1000 1010 1% M2
1522 1536 1% M3
2950 2991 1% M2
4710 4782 2% M2
10200 10410 2% M2
33000 33900 3% M2
100300 95000 -5% M2
Capacitance
Cap M MM.03
0.0038 0.004 5% M1
0.00973 0.01 3% M1
0.023 0.021 -9% M1
0.92 0.93 1% M1
1.007 1.01 0% M1
2.021 2.06 2% M1
22 21 -5% M1
48 46.2 -4% M1
103 101 -2% M1
322 378 17% M1
978 2230 128% M1
Regards,
Malc.
"Louie" <beavisnbutthead@softhome.net> wrote in message
news:xvE_a.96191$Vt6.31811@rwcrnsc52.ops.asp.att.net...
can someone tell me how to test/measure an inductor on a power supply
circuit board. can it be done in circuit with a VOM?
TIA
louie
L
Louie
Guest
Peter Parker wrote:
thanx, Louie
that's also a damn good idea. i think i got an old Hz meter somewhere.My own inductance measuring (though for smaller coils) is with an RF
oscillator and
a frequency counter (0-4 MHz built into a multimeter). The inductance is
calculated
from the frequency. Cost about $10-20 to build.
thanx, Louie
L
Louie
Guest
John Crighton wrote:
visible sign of damage anywhere, so all i could do was measure some of
the resistors, check the diodes, and get a new VR chip.
it takes a raw 110 input rectified and filtered. that part is OK. so
i'm gonna replace the chip and start with a 12 volt ac input and see
what it does.
i'm interested in how you made a welder. can you tell me the design?
thanx, louie
what i'm repairing is a switch mode PS for a projection TV. there's noLouie, that is about as much as I can help you
with your inductor problem. If you tell us what
you are building or repairing then maybe Phil
or some other members of the gang will chip in
with some suggestions.
visible sign of damage anywhere, so all i could do was measure some of
the resistors, check the diodes, and get a new VR chip.
it takes a raw 110 input rectified and filtered. that part is OK. so
i'm gonna replace the chip and start with a 12 volt ac input and see
what it does.
i'm interested in how you made a welder. can you tell me the design?
thanx, louie
L
Louie
Guest
Malcolm Faed wrote:
you.
thanks Malcolm
louie
now THAT sounds pretty awesome. i will totally try that and get back toHere is an almost free LCR meter, if you already have a PC with a sound
card.
http://www.i-adrian.home.ro/ (follow the Multimeter link)
you.
thanks Malcolm
louie
Here are the results of some tests I did.
=====================================
Sound Card LCR Meter Comparison
R = 99.1
Resistance
DSE DMM MM.03 % Difference
47.2 47.7 1% M2
460 465 1% M2
1000 1010 1% M2
1522 1536 1% M3
2950 2991 1% M2
4710 4782 2% M2
10200 10410 2% M2
33000 33900 3% M2
100300 95000 -5% M2
Capacitance
Cap M MM.03
0.0038 0.004 5% M1
0.00973 0.01 3% M1
0.023 0.021 -9% M1
0.92 0.93 1% M1
1.007 1.01 0% M1
2.021 2.06 2% M1
22 21 -5% M1
48 46.2 -4% M1
103 101 -2% M1
322 378 17% M1
978 2230 128% M1
Regards,
Malc.
"Louie" <beavisnbutthead@softhome.net> wrote in message
news:xvE_a.96191$Vt6.31811@rwcrnsc52.ops.asp.att.net...
can someone tell me how to test/measure an inductor on a power supply
circuit board. can it be done in circuit with a VOM?
TIA
louie
L
Louie
Guest
John Crighton wrote:
well those were some good links for arc welders. i hope to eventually
have one of my own.
as for the power supply, i'm going to set up an artificial load on the
output and put a low voltage on the input and see what i can come up
with. problem is, there's one unknown variable that i can't figure.
the supply has six output pins: ground, one regulated output that goes
back to the control curcuit, three more outputs, and one input comming
back from the external load that also goes to the control circuit. it
may be that without that external input it just won't do anything.
do you know why there would be a signal comming bck from the TV to the
control?
thanks, louie
well those were some good links for arc welders. i hope to eventually
have one of my own.
as for the power supply, i'm going to set up an artificial load on the
output and put a low voltage on the input and see what i can come up
with. problem is, there's one unknown variable that i can't figure.
the supply has six output pins: ground, one regulated output that goes
back to the control curcuit, three more outputs, and one input comming
back from the external load that also goes to the control circuit. it
may be that without that external input it just won't do anything.
do you know why there would be a signal comming bck from the TV to the
control?
thanks, louie
J
John Crighton
Guest
On Thu, 21 Aug 2003 23:24:18 GMT, Louie <beavisnbutthead@softhome.net>
wrote:
I can only guess that this is some sort of safety feature to shut
the power supply down if something goes wrong with the TV.
I am assuming that you have the circuit diagram or service
booklet for this projection TV you are working on. If not
try and get a diagram.
There are a lot of guys on this group who are experienced
in TV and video repair. Post the make and model number
of your TV, a description of the fault and all the things you
have checked. Some one on this group just might have
some experience of your particular fault. Local knowledge
can save a lot of head aches.
Is the power supply you are working on, a removable
module? If so, your idea of using an assortment of loads
to test it sounds good. You just have to work out what
to do with that control signal that may be shutting the
supply down. The supply might not be faulty at all.
Sounds like you are having a good wrestling match
with that fault. Over to you Louie for the model details.
Regards,
John Crighton
Hornsby
wrote:
Hello Louie,as for the power supply, i'm going to set up an artificial load on the
output and put a low voltage on the input and see what i can come up
with. problem is, there's one unknown variable that i can't figure.
the supply has six output pins: ground, one regulated output that goes
back to the control curcuit, three more outputs, and one input comming
back from the external load that also goes to the control circuit. it
may be that without that external input it just won't do anything.
do you know why there would be a signal comming bck from the TV to the
control?
I can only guess that this is some sort of safety feature to shut
the power supply down if something goes wrong with the TV.
I am assuming that you have the circuit diagram or service
booklet for this projection TV you are working on. If not
try and get a diagram.
There are a lot of guys on this group who are experienced
in TV and video repair. Post the make and model number
of your TV, a description of the fault and all the things you
have checked. Some one on this group just might have
some experience of your particular fault. Local knowledge
can save a lot of head aches.
Is the power supply you are working on, a removable
module? If so, your idea of using an assortment of loads
to test it sounds good. You just have to work out what
to do with that control signal that may be shutting the
supply down. The supply might not be faulty at all.
Sounds like you are having a good wrestling match
with that fault. Over to you Louie for the model details.
Regards,
John Crighton
Hornsby