Monitor makes loud buzzing sound when UPS is on Battery

[zack]

I'm using an APC BR1500 as a battery backup unit. Whenever I disconnect
it from the AC source and it switches to battery mode, my monitor makes
a loud buzzing sound, which is similar to the sound coming from the UPS,
but louder.

I'm assuming this is because when on battery mode, it does not output a
pure sine wave, but a "stepped sine wave". The noise doesn't really
bother me, since it only happens on a power outage, but I am worried
that this could damage my monitor. I am using an SGI GDM-5411 monitor,
which i'm told is the same electronically as a Sony GDM-F500R, which is
more common.

Should I be worried about this buzzing noise ? It doesn't affect the
image at all. The image is still crisp, clear, and bright, with no
distortions while using the battery.

 

[Richard Crowley]

I'm using an APC BR1500 as a battery backup unit. Whenever I disconnect
it from the AC source and it switches to battery mode, my monitor makes
a loud buzzing sound, which is similar to the sound coming from the UPS,
but louder.

I'm assuming this is because when on battery mode, it does not output a
pure sine wave, but a "stepped sine wave". The noise doesn't really
bother me, since it only happens on a power outage, but I am worried
that this could damage my monitor. I am using an SGI GDM-5411 monitor,
which i'm told is the same electronically as a Sony GDM-F500R, which is
more common.

Should I be worried about this buzzing noise ? It doesn't affect the
image at all. The image is still crisp, clear, and bright, with no
distortions while using the battery.

Doesn't sound all that healthy to me. I wouldn't run it for any longer
than it takes to shut-down in an orderly manner while waiting for the
mains to return.

 

[Howard Henry Schlunder]

in message

I'm using an APC BR1500 as a battery backup unit.
...
Should I be worried about this buzzing noise ? It doesn't affect the
image at all. The image is still crisp, clear, and bright, with no
distortions while using the battery.

Unless it was extremely loud, it wouldn't bother me. The APC BR1500 is
designed for computer loads. Although stepped-sine/square waves usually
cause higher peak currents to occur in bridge rectifiers and capacitors, I
can't see it adversly affecting the switch mode power supplies found in
monitors and other computer equipment in any serious way (at least when used
for only minutes at a time). Although I can't recommend doing so, if you
opened your monitor up and removed any less-than-critically-important
magnetic components (like a lossy ferrite core commonly found wrapped around
the mains input wires), you would probably decrease the audible buzz.

Howard Henry Schlunder

 

[AC/DCdude17]

X-No-Archive: Yes

in message


Unless it was extremely loud, it wouldn't bother me. The APC BR1500 is
designed for computer loads. Although stepped-sine/square waves usually
cause higher peak currents to occur in bridge rectifiers and capacitors, I
can't see it adversly affecting the switch mode power supplies found in
monitors and other computer equipment in any serious way (at least when used
for only minutes at a time).

Although I can't recommend doing so, if you
opened your monitor up and removed any less-than-critically-important
magnetic components (like a lossy ferrite core commonly found wrapped around
the mains input wires), you would probably decrease the audible buzz.

This might make it more psychologically pleasing, but it aggrevates the
problem. The front-end ferrite core inductors found inside the monitor power
supply minimizes the amount of high frequency interference traveling into power
line and it's also a reactor. When you take out the reactors, you further
decrease Irise time increasing peak current especially if the UPS is large and
has a low source impedance.

 

[zack]

Doesn't sound all that healthy to me. I wouldn't run it for any longer
than it takes to shut-down in an orderly manner while waiting for the
mains to return.

I think what I might do is just plug the monitor into a non-battery
powered outlet, and if the electricity does happen to go out while I am
at the computer, I can plug it into the battery powered outlet for a
short period of time, giving me time to shut down. Because my computer
might be off one day while I am not home, and since it makes the same
noise when the monitor is off, it would do this for at least 4 hours.

By the way, on the bottom of this device, it says: "The output of this
device is not sinusoidal. It has a total harmonic distortion of 67% and
a maximum single harmonic of 40%." What does that 40% value mean? I now
understand why they don't advertise this in the specifications on their
web site.

 

[zack]

Doesn't sound all that healthy to me. I wouldn't run it for any longer
than it takes to shut-down in an orderly manner while waiting for the
mains to return.

I think what I might do is just plug the monitor into a non-battery
powered outlet, and if the electricity does happen to go out while I am
at the computer, I can plug it into the battery powered outlet for a
short period of time, giving me time to shut down. Because my computer
might be off one day while I am not home, and since it makes the same
noise when the monitor is off, it would do this for at least 4 hours.

By the way, on the bottom of this device, it says: "The output of this
device is not sinusoidal. It has a total harmonic distortion of 67% and
a maximum single harmonic of 40%." What does that 40% value mean? I now
understand why they don't advertise this in the specifications on their
web site.

 

[Nico Coesel]

I think what I might do is just plug the monitor into a non-battery
powered outlet, and if the electricity does happen to go out while I am
at the computer, I can plug it into the battery powered outlet for a
short period of time, giving me time to shut down. Because my computer

That's not going to work. The UPS will overload either because of the
rush-in current of the monitor or the degauss coil. If you want to
have an image when the power goes out, disable power savings on the
monitor and power if from an UPS output.

 

[Kevin McMurtrie]

I'm using an APC BR1500 as a battery backup unit. Whenever I disconnect
it from the AC source and it switches to battery mode, my monitor makes
a loud buzzing sound, which is similar to the sound coming from the UPS,
but louder.

I'm assuming this is because when on battery mode, it does not output a
pure sine wave, but a "stepped sine wave". The noise doesn't really
bother me, since it only happens on a power outage, but I am worried
that this could damage my monitor. I am using an SGI GDM-5411 monitor,
which i'm told is the same electronically as a Sony GDM-F500R, which is
more common.

Should I be worried about this buzzing noise ? It doesn't affect the
image at all. The image is still crisp, clear, and bright, with no
distortions while using the battery.

The RF filters on the monitor's power input are buzzing. I wouldn't
worry about it.

 

[Rowbotth]

The RF filters on the monitor's power input are buzzing. I wouldn't
worry about it.

So you believe that the DC - AC Conversion within the UPS is giving a
waveform that is doing no damage to the monitor?

I'd think it would be best to get off the computer during a storm that
shuts off the power, personally. (The UPS shoulld be used to shut down
in an orderly fashion so nothing is lost, but that is all.)

Or what?

HR.