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Default 12v inverters - Output voltage too high?

I know this is a metalworking site, but there is quite a bit of expertise on subjects like this here.

I just bought a 200/300Watt 230v inverter. I attached it to a car battery on the bench (nothing else attached) and plugged in a few lamps. The output measured 330v with loads of 50 and 150 watts. The lights did seem brighter, but not excessively so. The voltmeter is a cheapie, but seems generally accurate. I know that these devices produce a modified sinewave, and I should expect a different reading, but I thought the reading should be lower if anything. Is this inverter a dud, or do I just not know how to measure?

Thanks
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Default 12v inverters - Output voltage too high?

On 7/9/2015 2:47 AM, robobass wrote:
I know this is a metalworking site, but there is quite a bit of expertise on subjects like this here.

I just bought a 200/300Watt 230v inverter. I attached it to a car battery on the bench (nothing else attached) and plugged in a few lamps. The output measured 330v with loads of 50 and 150 watts. The lights did seem brighter, but not excessively so. The voltmeter is a cheapie, but seems generally accurate. I know that these devices produce a modified sinewave, and I should expect a different reading, but I thought the reading should be lower if anything. Is this inverter a dud, or do I just not know how to measure?

Thanks

Probably the latter...
But
since you provided zero information about the inverter,
zero information about the lamps,
zero information about the meter,
It's hard to tell.

That the lamps didn't explode suggests you may not have
330V...maybe...depends...
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Default 12v inverters - Output voltage too high?

On Thursday, July 9, 2015 at 12:10:02 PM UTC+2, mike wrote:
On 7/9/2015 2:47 AM, robobass wrote:
I know this is a metalworking site, but there is quite a bit of expertise on subjects like this here.

I just bought a 200/300Watt 230v inverter. I attached it to a car battery on the bench (nothing else attached) and plugged in a few lamps. The output measured 330v with loads of 50 and 150 watts. The lights did seem brighter, but not excessively so. The voltmeter is a cheapie, but seems generally accurate. I know that these devices produce a modified sinewave, and I should expect a different reading, but I thought the reading should be lower if anything. Is this inverter a dud, or do I just not know how to measure?

Thanks

Probably the latter...
But
since you provided zero information about the inverter,
zero information about the lamps,
zero information about the meter,
It's hard to tell.

That the lamps didn't explode suggests you may not have
330V...maybe...depends...


Well, Have a nice day to you too!
Here is the picture of the inverter.
http://i.ebayimg.com/t/SPANNUNGSWANDLER-200W-300W-12V-230V-WECHSELRICHTER-INVERTER-USB-PKW-LKW-BATTERIE-/00/s/ODAwWDgwMA==/z/18IAAOSw3ydVhsoL/$_57..JPG
It lists specs:

Eingangsspannung: 12V DC (10-15V)
Ausgangsspanung: 230V (AC) +/- 10%
Effizienz: 85%
optimale Arbeitstemperatur: 5 - 45°C
Kühlungsmethode: Lüfter
Dauerleistung: 200W
Spitzenleistung: 300W

I know it's in German, but it should be clear even if you don't speak it. I don't have like a schematic diagram for it or anything. Bought on Ebay.

The lamps were two 220v 50w halogen spots and a 53w Edison bulb.

The meter is a typical multimeter you get from an electronics shop for under 50 bucks. It measures the mains at 220v.

What specific information do you suggest I provide?
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Default 12v inverters - Output voltage too high?

"robobass" wrote in message
...
I know this is a metalworking site, but there is quite a bit of
expertise on subjects like this here.

I just bought a 200/300Watt 230v inverter. I attached it to a car
battery on the bench (nothing else attached) and plugged in a few
lamps. The output measured 330v with loads of 50 and 150 watts. The
lights did seem brighter, but not excessively so. The voltmeter is a
cheapie, but seems generally accurate. I know that these devices
produce a modified sinewave, and I should expect a different reading,
but I thought the reading should be lower if anything. Is this
inverter a dud, or do I just not know how to measure?

Thanks

================

https://www.automationdirect.com/sta.../sj100/ch6.pdf
"Note 3: A general-purpose digital volt meter (DVM) is not usually
suitable to measure
a distorted waveform (not pure sinusoid)."


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Default 12v inverters - Output voltage too high?

On 7/9/2015 3:32 AM, robobass wrote:
On Thursday, July 9, 2015 at 12:10:02 PM UTC+2, mike wrote:
On 7/9/2015 2:47 AM, robobass wrote:
I know this is a metalworking site, but there is quite a bit of expertise on subjects like this here.

I just bought a 200/300Watt 230v inverter. I attached it to a car battery on the bench (nothing else attached) and plugged in a few lamps. The output measured 330v with loads of 50 and 150 watts. The lights did seem brighter, but not excessively so. The voltmeter is a cheapie, but seems generally accurate. I know that these devices produce a modified sinewave, and I should expect a different reading, but I thought the reading should be lower if anything. Is this inverter a dud, or do I just not know how to measure?

Thanks

Probably the latter...
But
since you provided zero information about the inverter,
zero information about the lamps,
zero information about the meter,
It's hard to tell.

That the lamps didn't explode suggests you may not have
330V...maybe...depends...


Well, Have a nice day to you too!
Here is the picture of the inverter.
http://i.ebayimg.com/t/SPANNUNGSWANDLER-200W-300W-12V-230V-WECHSELRICHTER-INVERTER-USB-PKW-LKW-BATTERIE-/00/s/ODAwWDgwMA==/z/18IAAOSw3ydVhsoL/$_57.JPG
It lists specs:

Eingangsspannung: 12V DC (10-15V)
Ausgangsspanung: 230V (AC) +/- 10%
Effizienz: 85%
optimale Arbeitstemperatur: 5 - 45°C
Kühlungsmethode: Lüfter
Dauerleistung: 200W
Spitzenleistung: 300W

I know it's in German, but it should be clear even if you don't speak it. I don't have like a schematic diagram for it or anything. Bought on Ebay.

The lamps were two 220v 50w halogen spots and a 53w Edison bulb.

The meter is a typical multimeter you get from an electronics shop for under 50 bucks. It measures the mains at 220v.

What specific information do you suggest I provide?

Well..I don't do German and the text tells nothing about the waveform
supplied. The link is just a picture.

There is no such thing as a typical multimeter. Your results are
atypical, so exactly what the meter measures might be the clue.

I've never experimented with Halogen, but I expect that 330V
would burn a 220V one out rather quickly.

A modified sinewave converter typically puts out the peak voltage
of the 230VAC RMS spec. (~320V) and sets the duty factor to provide
an RMS value of 230V.

Sounds like a meter problem to me, but can't tell cuz it's still a
mystery meter.






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Default 12v inverters - Output voltage too high?

Trying to think of another way to measure, I attached a small 220v axial fan to the inverter. The pitch of the fan was about a major third higher than when run on the mains, meaning about 25% higher.

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Default 12v inverters - Output voltage too high?

"robobass" wrote in message
...
On Thursday, July 9, 2015 at 12:10:02 PM UTC+2, mike wrote:
On 7/9/2015 2:47 AM, robobass wrote:
I know this is a metalworking site, but there is quite a bit of
expertise on subjects like this here.

I just bought a 200/300Watt 230v inverter. I attached it to a car
battery on the bench (nothing else attached) and plugged in a few
lamps. The output measured 330v with loads of 50 and 150 watts.
The lights did seem brighter, but not excessively so. The
voltmeter is a cheapie, but seems generally accurate. I know that
these devices produce a modified sinewave, and I should expect a
different reading, but I thought the reading should be lower if
anything. Is this inverter a dud, or do I just not know how to
measure?

Thanks

Probably the latter...
But
since you provided zero information about the inverter,
zero information about the lamps,
zero information about the meter,
It's hard to tell.

That the lamps didn't explode suggests you may not have
330V...maybe...depends...


Well, Have a nice day to you too!
Here is the picture of the inverter.
http://i.ebayimg.com/t/SPANNUNGSWANDLER-200W-300W-12V-230V-WECHSELRICHTER-INVERTER-USB-PKW-LKW-BATTERIE-/00/s/ODAwWDgwMA==/z/18IAAOSw3ydVhsoL/$_57.JPG
It lists specs:

Eingangsspannung: 12V DC (10-15V)
Ausgangsspanung: 230V (AC) +/- 10%
Effizienz: 85%
optimale Arbeitstemperatur: 5 - 45°C
Kühlungsmethode: Lüfter
Dauerleistung: 200W
Spitzenleistung: 300W

I know it's in German, but it should be clear even if you don't speak
it. I don't have like a schematic diagram for it or anything. Bought
on Ebay.

The lamps were two 220v 50w halogen spots and a 53w Edison bulb.

The meter is a typical multimeter you get from an electronics shop for
under 50 bucks. It measures the mains at 220v.

What specific information do you suggest I provide?

=============

The German power line frequency is 50 Hz.
Dauerleistung is continuouspower, Spitzenleistung is peakpower.

You really need a scope to measure the output voltage, frequency and
duty cycle. The voltage of a changing signal is calculated from its
heating power, which varies as the square of the voltage, not its
average which is what a non-RMS meter displays. They fudge their
average reading to show what the RMS value should be, but only for a
sinusoidal waveform.

http://www.electronics-tutorials.ws/...s-voltage.html

-jsw


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Default 12v inverters - Output voltage too high?

As to the meter, I actually found the manual online and the only relevant thing was "Corrected mean corresponds to the sinusoidal RMS".

Not having a scope or the knowledge how to use one, I tried another test. I plugged in a 230vac to 24vac transformer in parallel with a 60w tungsten bulb and compared the no-load voltage of the step down transformer. It was practically the same, as was the observable bulb brightness, between running off the mains or the inverter. So, I guess I'm OK. The fan test is still worrisome for me though.

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Default 12v inverters - Output voltage too high?

On 09/07/15 12:15, robobass wrote:
Trying to think of another way to measure, I attached a small 220v axial fan to the inverter. The pitch of the fan was about a major third higher than when run on the mains, meaning about 25% higher.

Some types of of AC motor respond to voltage control of the speed, IIRC
shaded pole was one. I have a Comair Rotron axial fan and have used it
with an EBM Ziehl speed controller intended for fan speed control to
slow it down but it was run off 240V 50Hz mains, I presume if you can
slow them down by reducing the voltage then the opposite may also hold
if your inverter is seen to put out a higher voltage.
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Default 12v inverters - Output voltage too high?

On Thu, 9 Jul 2015 03:32:18 -0700 (PDT), robobass
wrote:

On Thursday, July 9, 2015 at 12:10:02 PM UTC+2, mike wrote:
On 7/9/2015 2:47 AM, robobass wrote:
I know this is a metalworking site, but there is quite a bit of expertise on subjects like this here.

I just bought a 200/300Watt 230v inverter. I attached it to a car battery on the bench (nothing else attached) and plugged in a few lamps. The output measured 330v with loads of 50 and 150 watts. The lights did seem brighter, but not excessively so. The voltmeter is a cheapie, but seems generally accurate. I know that these devices produce a modified sinewave, and I should expect a different reading, but I thought the reading should be lower if anything. Is this inverter a dud, or do I just not know how to measure?

Thanks

Probably the latter...
But
since you provided zero information about the inverter,
zero information about the lamps,
zero information about the meter,
It's hard to tell.

That the lamps didn't explode suggests you may not have
330V...maybe...depends...


Well, Have a nice day to you too!
Here is the picture of the inverter.
http://i.ebayimg.com/t/SPANNUNGSWANDLER-200W-300W-12V-230V-WECHSELRICHTER-INVERTER-USB-PKW-LKW-BATTERIE-/00/s/ODAwWDgwMA==/z/18IAAOSw3ydVhsoL/$_57.JPG
It lists specs:

Eingangsspannung: 12V DC (10-15V)
Ausgangsspanung: 230V (AC) +/- 10%
Effizienz: 85%
optimale Arbeitstemperatur: 5 - 45°C
Kühlungsmethode: Lüfter
Dauerleistung: 200W
Spitzenleistung: 300W

I know it's in German, but it should be clear even if you don't speak it. I don't have like a schematic diagram for it or anything. Bought on Ebay.

The lamps were two 220v 50w halogen spots and a 53w Edison bulb.

The meter is a typical multimeter you get from an electronics shop for under 50 bucks. It measures the mains at 220v.

What specific information do you suggest I provide?


Sounds like a bogus inverter. I'd take it back (with meter in hand)
and check the replacement or go to a different vendor. 5% is the
usual tolerance for power fluctuation.

--
We are always the same age inside.
-- Gertrude Stein


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Default 12v inverters - Output voltage too high?

I presume if you can
slow them down by reducing the voltage then the opposite may also hold
if your inverter is seen to put out a higher voltage.


Right. The frequency should still be around 50 Hz with the inverter. All this "RMS" and "Modified Sinewave" stuff is way out of my pay grade, but I assume that different types of load will respond differently to the voltage produced by a cheap inverter compared to what comes from the local power company. I was aware that the measurement with my multimeter would be dodgy because of this, but I kind of freaked when I saw 330v. I'm starting to think that I may have nothing to worry about. Any other laymen tests I could do? I'm only going camping.
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Default 12v inverters - Output voltage too high?

On Thu, 09 Jul 2015 04:02:35 -0700, mike wrote:

On 7/9/2015 3:32 AM, robobass wrote:
On Thursday, July 9, 2015 at 12:10:02 PM UTC+2, mike wrote:
On 7/9/2015 2:47 AM, robobass wrote:
I know this is a metalworking site, but there is quite a bit of expertise on subjects like this here.

I just bought a 200/300Watt 230v inverter. I attached it to a car battery on the bench (nothing else attached) and plugged in a few lamps. The output measured 330v with loads of 50 and 150 watts. The lights did seem brighter, but not excessively so. The voltmeter is a cheapie, but seems generally accurate. I know that these devices produce a modified sinewave, and I should expect a different reading, but I thought the reading should be lower if anything. Is this inverter a dud, or do I just not know how to measure?

Thanks

Probably the latter...
But
since you provided zero information about the inverter,
zero information about the lamps,
zero information about the meter,
It's hard to tell.

That the lamps didn't explode suggests you may not have
330V...maybe...depends...


Well, Have a nice day to you too!
Here is the picture of the inverter.
http://i.ebayimg.com/t/SPANNUNGSWANDLER-200W-300W-12V-230V-WECHSELRICHTER-INVERTER-USB-PKW-LKW-BATTERIE-/00/s/ODAwWDgwMA==/z/18IAAOSw3ydVhsoL/$_57.JPG
It lists specs:

Eingangsspannung: 12V DC (10-15V)
Ausgangsspanung: 230V (AC) +/- 10%
Effizienz: 85%
optimale Arbeitstemperatur: 5 - 45°C
Kühlungsmethode: Lüfter
Dauerleistung: 200W
Spitzenleistung: 300W

I know it's in German, but it should be clear even if you don't speak it. I don't have like a schematic diagram for it or anything. Bought on Ebay.

The lamps were two 220v 50w halogen spots and a 53w Edison bulb.

The meter is a typical multimeter you get from an electronics shop for under 50 bucks. It measures the mains at 220v.

What specific information do you suggest I provide?

Well..I don't do German and the text tells nothing about the waveform
supplied. The link is just a picture.

There is no such thing as a typical multimeter. Your results are
atypical, so exactly what the meter measures might be the clue.


mike, if the meter measures mains at 220 and the inverter at 330 (WITH
a load), I would trust the meter reading. YMMV

Every meter I've ever used has measured within a couple percent of any
others I've tested them with, so I consider that a typical multimeter.
If you need more precision, buy an expensive multimeter with metrology
documentation and certification. The rest of us can use the $5 HF
versions with impunity, joy, and a _much_ lower cost.

--
We are always the same age inside.
-- Gertrude Stein
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Default 12v inverters - Output voltage too high?

On 7/9/2015 6:40 AM, Larry Jaques wrote:
On Thu, 09 Jul 2015 04:02:35 -0700, mike wrote:

On 7/9/2015 3:32 AM, robobass wrote:
On Thursday, July 9, 2015 at 12:10:02 PM UTC+2, mike wrote:
On 7/9/2015 2:47 AM, robobass wrote:
I know this is a metalworking site, but there is quite a bit of expertise on subjects like this here.

I just bought a 200/300Watt 230v inverter. I attached it to a car battery on the bench (nothing else attached) and plugged in a few lamps. The output measured 330v with loads of 50 and 150 watts. The lights did seem brighter, but not excessively so. The voltmeter is a cheapie, but seems generally accurate. I know that these devices produce a modified sinewave, and I should expect a different reading, but I thought the reading should be lower if anything. Is this inverter a dud, or do I just not know how to measure?

Thanks

Probably the latter...
But
since you provided zero information about the inverter,
zero information about the lamps,
zero information about the meter,
It's hard to tell.

That the lamps didn't explode suggests you may not have
330V...maybe...depends...

Well, Have a nice day to you too!
Here is the picture of the inverter.
http://i.ebayimg.com/t/SPANNUNGSWANDLER-200W-300W-12V-230V-WECHSELRICHTER-INVERTER-USB-PKW-LKW-BATTERIE-/00/s/ODAwWDgwMA==/z/18IAAOSw3ydVhsoL/$_57.JPG
It lists specs:

Eingangsspannung: 12V DC (10-15V)
Ausgangsspanung: 230V (AC) +/- 10%
Effizienz: 85%
optimale Arbeitstemperatur: 5 - 45°C
Kühlungsmethode: Lüfter
Dauerleistung: 200W
Spitzenleistung: 300W

I know it's in German, but it should be clear even if you don't speak it. I don't have like a schematic diagram for it or anything. Bought on Ebay.

The lamps were two 220v 50w halogen spots and a 53w Edison bulb.

The meter is a typical multimeter you get from an electronics shop for under 50 bucks. It measures the mains at 220v.

What specific information do you suggest I provide?

Well..I don't do German and the text tells nothing about the waveform
supplied. The link is just a picture.

There is no such thing as a typical multimeter. Your results are
atypical, so exactly what the meter measures might be the clue.


mike, if the meter measures mains at 220 and the inverter at 330 (WITH
a load), I would trust the meter reading. YMMV


I can't come up with a
voltmeter topology that would produce the observed responses.
So, that's weird.
It's hard to judge a secret meter.

But!
How long will a 220V Halogen light burn on 330V?
I claim it ain't very long.
And the difference in brightness would be BIG.
That info alone suggests that the output ain't 330V RMS.

Sometimes, you just need a friend with a scope.

Every meter I've ever used has measured within a couple percent of any
others I've tested them with, so I consider that a typical multimeter.
If you need more precision, buy an expensive multimeter with metrology
documentation and certification. The rest of us can use the $5 HF
versions with impunity, joy, and a _much_ lower cost.


Typical??
Statistics are great when you are sizing a power plant or sewer system.
But, when YOU are the one who doesn't fit the pattern, the statistics
are no comfort. It's either pass or fail for your specific atypical
instance.
When the meter is a secret, conjecture is all you get.

Bottom line is that we'll probably never know.

--
We are always the same age inside.
-- Gertrude Stein


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Default 12v inverters - Output voltage too high?

On Thu, 9 Jul 2015 05:28:11 -0700 (PDT), robobass
wrote:

As to the meter, I actually found the manual online and the only relevant thing was "Corrected mean corresponds to the sinusoidal RMS".

Not having a scope or the knowledge how to use one, I tried another test. I plugged in a 230vac to 24vac transformer in parallel with a 60w tungsten bulb and compared the no-load voltage of the step down transformer. It was practically the same, as was the observable bulb brightness, between running off the mains or the inverter. So, I guess I'm OK. The fan test is still worrisome for me though.

Cheap inverters put out a stepped voltage that roughly corresponds to
a sine wave. Furthermore, the inverter will put out a higher voltage
when lightly loaded and the voltage will drop as more load is put on
the device. The stepped voltage may rise above the rated voltage
because the inverter maker is expecting the load to average the
voltage to the rated voltage. Try plugging an induction motor into the
thing and then measure the voltage. Your digital meter may not be very
good at averaging the stepped voltage output of the inverter and so
will show a higher peak voltage instead of the averaged voltage. An
analog meter would probably be more accurate for this measurement. If
you put a diode in series with one wire of an AC supply it will
rectify the AC into pulsed DC. If you then measure this DC voltage it
will be 1.414 times the measured AC voltage. This is because the sine
wave shape of the rising and falling AC voltage shows that it has a
peak value of 1.414 times the RMS voltage. And the RMS voltage of AC
devices is what is printed on the label as the voltage rating. So
your typical AC 120 volt rated motor is expected to run on AC that
peaks at 169.68 volts.
Eric
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"robobass" wrote in message
...
I presume if you can
slow them down by reducing the voltage then the opposite may also
hold
if your inverter is seen to put out a higher voltage.


Right. The frequency should still be around 50 Hz with the inverter.
All this "RMS" and "Modified Sinewave" stuff is way out of my pay
grade, but I assume that different types of load will respond
differently to the voltage produced by a cheap inverter compared to
what comes from the local power company. I was aware that the
measurement with my multimeter would be dodgy because of this, but I
kind of freaked when I saw 330v. I'm starting to think that I may have
nothing to worry about. Any other laymen tests I could do? I'm only
going camping.

============

If you have a (possibly sacrificial) way to heat water with the
inverter you could time how long a measured amount of room temperature
water takes to boil on the inverter and on Netzstrom. They should be
pretty close to each other.

-jsw




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"Jim Wilkins" wrote in message
...

"robobass" wrote in message
...
I presume if you can
slow them down by reducing the voltage then the opposite may also
hold
if your inverter is seen to put out a higher voltage.


Right. The frequency should still be around 50 Hz with the inverter.
All this "RMS" and "Modified Sinewave" stuff is way out of my pay
grade, but I assume that different types of load will respond
differently to the voltage produced by a cheap inverter compared to
what comes from the local power company. I was aware that the
measurement with my multimeter would be dodgy because of this, but I
kind of freaked when I saw 330v. I'm starting to think that I may
have nothing to worry about. Any other laymen tests I could do? I'm
only going camping.

============

If you have a (possibly sacrificial) way to heat water with the
inverter you could time how long a measured amount of room
temperature water takes to boil on the inverter and on Netzstrom.
They should be pretty close to each other.

-jsw


The first bubbles you see at around 80C will be dissolved air coming
out of solution, not steam.



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Default 12v inverters - Output voltage too high?

On 7/9/2015 5:47 AM, robobass wrote:
... The lights did seem brighter, but not excessively so. ...


Incandescent lamp _life_ is highly dependent upon RMS voltage. At 330v,
a 230v lamp's life would be very short! If you have a 220 to 110
transformer? If so, connect as a boost to your 220 to get a real 330v
and put one of you 220v lamps on it. The difference in brightness and
life will be dramatic. And will demonstrate that the inverter is not
really producing 230v RMS.

Bob

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Default 12v inverters - Output voltage too high?

Tell us the model number of the meter.

To get a proper (RMS) reading, you will need a 'true RMS' meter. Otherwise,
it reads the peak a nd scales that down by sqrt(2) which is only valid for a
sine wave. If you don't know what kind you've got, some electrical whiz can
tell you.

--
Paul Hovnanian
------------------------------------------------------------------
Shoot low, sheriff. They're riding Shetlands!

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Default 12v inverters - Output voltage too high?

On Thursday, July 9, 2015 at 6:57:08 AM UTC-4, Jim Wilkins wrote:


https://www.automationdirect.com/sta.../sj100/ch6.pdf
"Note 3: A general-purpose digital volt meter (DVM) is not usually
suitable to measure
a distorted waveform (not pure sinusoid)."


Amen to that. A nominal 230VAC (rms) sine wave will be 650VPP. and will read right around 230V on a "normal, cheap, non-rms" meter. A square wave with an RMS voltage of 230V will be 460VPP, but the cheap meter won't know what to make of it. Once you add the word "modified" to the waveform, all bets for an accurate reading are off with the cheap meter.

Later in the thread, it was suggested that plugging a transformer into the inverter and into the mains produced the same output voltage. That suggests to me that the transformer is filtering the waveform enough that the meter is less whacked out. My GUESS is that the inverter is doing what it's supposed to do, and the meter is just confused.
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On 7/9/2015 1:26 PM, Bob Engelhardt wrote:
.... is not
really producing 230v RMS.


Brain fart! _330v_



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On Thu, 09 Jul 2015 10:47:53 -0700, Paul Hovnanian P.E. wrote:

Tell us the model number of the meter.

To get a proper (RMS) reading, you will need a 'true RMS' meter.
Otherwise, it reads the peak a nd scales that down by sqrt(2) which is
only valid for a sine wave. If you don't know what kind you've got, some
electrical whiz can tell you.


I thought of that, but the most likely cheap-meter equivalent would be a
square wave, which would read lower.

I suppose that a meter that takes the average of the absolute value and
then scales _up_ may be off in this manner, however.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
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"Tim Wescott" wrote in message
...
On Thu, 09 Jul 2015 10:47:53 -0700, Paul Hovnanian P.E. wrote:

Tell us the model number of the meter.

To get a proper (RMS) reading, you will need a 'true RMS' meter.
Otherwise, it reads the peak a nd scales that down by sqrt(2) which
is
only valid for a sine wave. If you don't know what kind you've got,
some
electrical whiz can tell you.


I thought of that, but the most likely cheap-meter equivalent would
be a
square wave, which would read lower.

I suppose that a meter that takes the average of the absolute value
and
then scales _up_ may be off in this manner, however.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


http://www.escoglobal.com/resources/...rs/True_G2.pdf

-jsw


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Default 12v inverters - Output voltage too high?

On Thu, 9 Jul 2015 02:47:20 -0700 (PDT), robobass
wrote:

I know this is a metalworking site, but there is quite a bit of expertise on subjects like this here.

I just bought a 200/300Watt 230v inverter. I attached it to a car battery on the bench (nothing else attached) and plugged in a few lamps. The output measured 330v with loads of 50 and 150 watts. The lights did seem brighter, but not excessively so. The voltmeter is a cheapie, but seems generally accurate. I know that these devices produce a modified sinewave, and I should expect a different reading, but I thought the reading should be lower if anything. Is this inverter a dud, or do I just not know how to measure?

Thanks

You should read about 0.7 x the rated voltage on a modified square
wave inverter.
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On Fri, 10 Jul 2015 09:14:47 +1000, John G wrote:

wrote :
On Thu, 9 Jul 2015 02:47:20 -0700 (PDT), robobass
wrote:


I know this is a metalworking site, but there is quite a bit of expertise on
subjects like this here.

I just bought a 200/300Watt 230v inverter. I attached it to a car battery on
the bench (nothing else attached) and plugged in a few lamps. The output
measured 330v with loads of 50 and 150 watts. The lights did seem brighter,
but not excessively so. The voltmeter is a cheapie, but seems generally
accurate. I know that these devices produce a modified sinewave, and I
should expect a different reading, but I thought the reading should be lower
if anything. Is this inverter a dud, or do I just not know how to measure?

Thanks

You should read about 0.7 x the rated voltage on a modified square
wave inverter.


I am amazed no one has suggested using a good old Simpson 260 or
similar ANALOGUE meter and get the real answer.
All this waffle about transformers and peaks and average is typical of
the impractical answers so common in some of the electronics groups.
KISS Keep It Simple Stupid. :-?


Won't work any better than the DVM, it'll just give yet another
misleading value.

My impractical waffle is to use two identical lamps with clear
envelopes, a variac, and a voltmeter. Connect one lamp to the inverter
and the other to the variac. Arrange them so the filaments are nearly
superimposed as you look thru both envelopes. Adjust the variac so
there's no difference in the color of the of the two filaments.
Measure the output voltage of the variac - that's the RMS output of
the inverter, within, I'll wager, a couple percent.

Switch the lamps and repeat the experiment to check for any detectable
difference between them.

--
Ned Simmons


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Default 12v inverters - Output voltage too high?

On Thursday, July 9, 2015 at 5:47:23 AM UTC-4, robobass wrote:


I just bought a 200/300Watt 230v inverter. I attached it to a car battery on the bench (nothing else attached) and plugged in a few lamps. The output measured 330v with loads of 50 and 150 watts. The lights did seem brighter, but not excessively so. The voltmeter is a cheapie, but seems generally accurate. I know that these devices produce a modified sinewave, and I should expect a different reading, but I thought the reading should be lower if anything. Is this inverter a dud, or do I just not know how to measure?

Thanks


Obviously not a dud as it does produce AC. But the real question is does the inverter do what you bought it to do. And if so why do you care about the voltmeter reading? If it is just that you are curious why the voltmeter reads high, I think you need to see the waveform on some kind of a scope.

The suggestions to compare heating water and comparing lamp filament brightness will let you know what the power output is.

Dan

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Default 12v inverters - Output voltage too high?

It happens that Ned Simmons formulated :
On Fri, 10 Jul 2015 09:14:47 +1000, John G wrote:


wrote :
On Thu, 9 Jul 2015 02:47:20 -0700 (PDT), robobass
wrote:
I know this is a metalworking site, but there is quite a bit of expertise
on subjects like this here.

I just bought a 200/300Watt 230v inverter. I attached it to a car battery
on the bench (nothing else attached) and plugged in a few lamps. The
output measured 330v with loads of 50 and 150 watts. The lights did seem
brighter, but not excessively so. The voltmeter is a cheapie, but seems
generally accurate. I know that these devices produce a modified
sinewave, and I should expect a different reading, but I thought the
reading should be lower if anything. Is this inverter a dud, or do I just
not know how to measure?

Thanks
You should read about 0.7 x the rated voltage on a modified square
wave inverter.


I am amazed no one has suggested using a good old Simpson 260 or
similar ANALOGUE meter and get the real answer.
All this waffle about transformers and peaks and average is typical of
the impractical answers so common in some of the electronics groups.
KISS Keep It Simple Stupid. :-?


Won't work any better than the DVM, it'll just give yet another
misleading value.

are you sure?

My impractical waffle is to use two identical lamps with clear
envelopes, a variac, and a voltmeter. Connect one lamp to the inverter
and the other to the variac. Arrange them so the filaments are nearly
superimposed as you look thru both envelopes. Adjust the variac so
there's no difference in the color of the of the two filaments.
Measure the output voltage of the variac - that's the RMS output of
the inverter, within, I'll wager, a couple percent.


Switch the lamps and repeat the experiment to check for any detectable
difference between them.


How many people who ask Electric Questions in a Metalwaork Group have a
Variac sitting around for such experiments?

--
John G Sydney.
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Default 12v inverters - Output voltage too high?

On Thursday, July 9, 2015 at 9:02:02 PM UTC-4, John G wrote:



How many people who ask Electric Questions in a Metalwaork Group have a
Variac sitting around for such experiments?

--
John G Sydney.


I have several, but would have to look to see if any are rated for 240 volts.

Dan

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Default 12v inverters - Output voltage too high?

On Fri, 10 Jul 2015 11:01:54 +1000, John G wrote:

It happens that Ned Simmons formulated :
On Fri, 10 Jul 2015 09:14:47 +1000, John G wrote:


wrote :
On Thu, 9 Jul 2015 02:47:20 -0700 (PDT), robobass
wrote:
I know this is a metalworking site, but there is quite a bit of expertise
on subjects like this here.

I just bought a 200/300Watt 230v inverter. I attached it to a car battery
on the bench (nothing else attached) and plugged in a few lamps. The
output measured 330v with loads of 50 and 150 watts. The lights did seem
brighter, but not excessively so. The voltmeter is a cheapie, but seems
generally accurate. I know that these devices produce a modified
sinewave, and I should expect a different reading, but I thought the
reading should be lower if anything. Is this inverter a dud, or do I just
not know how to measure?

Thanks
You should read about 0.7 x the rated voltage on a modified square
wave inverter.

I am amazed no one has suggested using a good old Simpson 260 or
similar ANALOGUE meter and get the real answer.
All this waffle about transformers and peaks and average is typical of
the impractical answers so common in some of the electronics groups.
KISS Keep It Simple Stupid. :-?


Won't work any better than the DVM, it'll just give yet another
misleading value.

are you sure?


Quite sure.
http://www.fluke.com/fluke/uses/comu.../true-rmsfacts


My impractical waffle is to use two identical lamps with clear
envelopes, a variac, and a voltmeter. Connect one lamp to the inverter
and the other to the variac. Arrange them so the filaments are nearly
superimposed as you look thru both envelopes. Adjust the variac so
there's no difference in the color of the of the two filaments.
Measure the output voltage of the variac - that's the RMS output of
the inverter, within, I'll wager, a couple percent.


Switch the lamps and repeat the experiment to check for any detectable
difference between them.


How many people who ask Electric Questions in a Metalwaork Group have a
Variac sitting around for such experiments?


Good question. But if a fellow was curious enough, small used variacs
are easy to come by.

--
Ned Simmons
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Default 12v inverters - Output voltage too high?

On Fri, 10 Jul 2015 11:01:54 +1000, John G wrote:

It happens that Ned Simmons formulated :
On Fri, 10 Jul 2015 09:14:47 +1000, John G wrote:


wrote :
On Thu, 9 Jul 2015 02:47:20 -0700 (PDT), robobass
wrote:
I know this is a metalworking site, but there is quite a bit of expertise
on subjects like this here.

I just bought a 200/300Watt 230v inverter. I attached it to a car battery
on the bench (nothing else attached) and plugged in a few lamps. The
output measured 330v with loads of 50 and 150 watts. The lights did seem
brighter, but not excessively so. The voltmeter is a cheapie, but seems
generally accurate. I know that these devices produce a modified
sinewave, and I should expect a different reading, but I thought the
reading should be lower if anything. Is this inverter a dud, or do I just
not know how to measure?

Thanks
You should read about 0.7 x the rated voltage on a modified square
wave inverter.

I am amazed no one has suggested using a good old Simpson 260 or
similar ANALOGUE meter and get the real answer.
All this waffle about transformers and peaks and average is typical of
the impractical answers so common in some of the electronics groups.
KISS Keep It Simple Stupid. :-?


Won't work any better than the DVM, it'll just give yet another
misleading value.

are you sure?

My impractical waffle is to use two identical lamps with clear
envelopes, a variac, and a voltmeter. Connect one lamp to the inverter
and the other to the variac. Arrange them so the filaments are nearly
superimposed as you look thru both envelopes. Adjust the variac so
there's no difference in the color of the of the two filaments.
Measure the output voltage of the variac - that's the RMS output of
the inverter, within, I'll wager, a couple percent.


Switch the lamps and repeat the experiment to check for any detectable
difference between them.


How many people who ask Electric Questions in a Metalwaork Group have a
Variac sitting around for such experiments?

I've gat 4 or 5 of them- from itty bitty to HUGE.


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Default 12v inverters - Output voltage too high?

Anyone thought about using a "true RMS" meter.

CP

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Default 12v inverters - Output voltage too high?

On Thursday, July 9, 2015 at 9:29:58 AM UTC-7, Jim Wilkins wrote:

[about odd AC measurements on a DC/AC inverter]

If you have a (possibly sacrificial) way to heat water with the
inverter you could time how long a measured amount of room temperature
water takes to boil on the inverter and on Netzstrom. They should be
pretty close to each other.


Bingo! An electric coffeemaker's brew time for a given water fill is
a better RMS voltage meter than most inexpensive electronic meters.
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Default 12v inverters - Output voltage too high?

On Friday, July 10, 2015 at 5:11:27 AM UTC+2, whit3rd wrote:
On Thursday, July 9, 2015 at 9:29:58 AM UTC-7, Jim Wilkins wrote:

[about odd AC measurements on a DC/AC inverter]

If you have a (possibly sacrificial) way to heat water with the
inverter you could time how long a measured amount of room temperature
water takes to boil on the inverter and on Netzstrom. They should be
pretty close to each other.


Bingo! An electric coffeemaker's brew time for a given water fill is
a better RMS voltage meter than most inexpensive electronic meters.


I thought of that, but my water kettle is 2200w. As to getting a scope or variac or true RMS meter, I'm the only one I know who even owns a DVM! Some of my friends are aircraft engineers, but couldn't jump start a car with a gun to their head. No, I'm all alone here as to equipment. I think I'll just trust my step down transformer test. I was only worried that with such a high reading I might burn up a power supply or maybe even have a fire.

Thanks all!

PS. The meter is a TopCraft TMMH-930. You can download the manual, but would need to speak either Dutch or German to read it!
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Default 12v inverters - Output voltage too high?

"John G" wrote in message
...
It happens that Ned Simmons formulated :
On Fri, 10 Jul 2015 09:14:47 +1000, John G
wrote:


wrote :
On Thu, 9 Jul 2015 02:47:20 -0700 (PDT), robobass
wrote:
I know this is a metalworking site, but there is quite a bit of
expertise on subjects like this here. I just bought a
200/300Watt 230v inverter. I attached it to a car battery on
the bench (nothing else attached) and plugged in a few lamps.
The output measured 330v with loads of 50 and 150 watts. The
lights did seem brighter, but not excessively so. The voltmeter
is a cheapie, but seems generally accurate. I know that these
devices produce a modified sinewave, and I should expect a
different reading, but I thought the reading should be lower if
anything. Is this inverter a dud, or do I just not know how to
measure? Thanks
You should read about 0.7 x the rated voltage on a modified
square
wave inverter.

I am amazed no one has suggested using a good old Simpson 260 or
similar ANALOGUE meter and get the real answer.
All this waffle about transformers and peaks and average is
typical of the impractical answers so common in some of the
electronics groups.
KISS Keep It Simple Stupid. :-?


Won't work any better than the DVM, it'll just give yet another
misleading value.

are you sure?

My impractical waffle is to use two identical lamps with clear
envelopes, a variac, and a voltmeter. Connect one lamp to the
inverter
and the other to the variac. Arrange them so the filaments are
nearly
superimposed as you look thru both envelopes. Adjust the variac so
there's no difference in the color of the of the two filaments.
Measure the output voltage of the variac - that's the RMS output of
the inverter, within, I'll wager, a couple percent.


Switch the lamps and repeat the experiment to check for any
detectable
difference between them.


How many people who ask Electric Questions in a Metalwaork Group
have a Variac sitting around for such experiments?

--
John G Sydney.


I have Variacs and Powerstats from 3A to 20A, 140V and 280V, and
metalwaorked a new set of brass brushes for the 20A one. They are
basic necessities for alternate energy experimenting, along with
variable DC lab supplies. Yesterday I used a lab supply to see how
much USB current my "new" smart phone draws, before risking a laptop.

An SCR dimmer distorts the waveform and may not give the right answer.

The other test is to plug in everything you plan to use before you go,
to see if they survive.

-jsw


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"whit3rd" wrote in message
...
On Thursday, July 9, 2015 at 9:29:58 AM UTC-7, Jim Wilkins wrote:

[about odd AC measurements on a DC/AC inverter]

If you have a (possibly sacrificial) way to heat water with the
inverter you could time how long a measured amount of room
temperature
water takes to boil on the inverter and on Netzstrom. They should
be
pretty close to each other.


Bingo! An electric coffeemaker's brew time for a given water fill
is
a better RMS voltage meter than most inexpensive electronic meters.


The heater's power draw would have to be within the capacity of the
inverter and battery, perhaps an immersion heater or single-serving
hot pot for a dorm room or office desk. A 1000W coffee maker would
pull over 80A from the 12V vehicle battery.

-jsw




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"robobass" wrote in message
...
On Friday, July 10, 2015 at 5:11:27 AM UTC+2, whit3rd wrote:
On Thursday, July 9, 2015 at 9:29:58 AM UTC-7, Jim Wilkins wrote:

[about odd AC measurements on a DC/AC inverter]

If you have a (possibly sacrificial) way to heat water with the
inverter you could time how long a measured amount of room
temperature
water takes to boil on the inverter and on Netzstrom. They should
be
pretty close to each other.


Bingo! An electric coffeemaker's brew time for a given water fill
is
a better RMS voltage meter than most inexpensive electronic meters.


I thought of that, but my water kettle is 2200w. As to getting a scope
or variac or true RMS meter, I'm the only one I know who even owns a
DVM! Some of my friends are aircraft engineers, but couldn't jump
start a car with a gun to their head. No, I'm all alone here as to
equipment. I think I'll just trust my step down transformer test. I
was only worried that with such a high reading I might burn up a power
supply or maybe even have a fire.

Thanks all!

PS. The meter is a TopCraft TMMH-930. You can download the manual, but
would need to speak either Dutch or German to read it!

===
I'm back on dialup for a while, no joy trying to download a German
Bedienungsanleitung, and I don't read Dutch.
-jsw


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On Friday, July 10, 2015 at 1:27:55 PM UTC+2, Jim Wilkins wrote:
"whit3rd" wrote in message
...
On Thursday, July 9, 2015 at 9:29:58 AM UTC-7, Jim Wilkins wrote:

[about odd AC measurements on a DC/AC inverter]

If you have a (possibly sacrificial) way to heat water with the
inverter you could time how long a measured amount of room
temperature
water takes to boil on the inverter and on Netzstrom. They should
be
pretty close to each other.


Bingo! An electric coffeemaker's brew time for a given water fill
is
a better RMS voltage meter than most inexpensive electronic meters.


The heater's power draw would have to be within the capacity of the
inverter and battery, perhaps an immersion heater or single-serving
hot pot for a dorm room or office desk. A 1000W coffee maker would
pull over 80A from the 12V vehicle battery.

-jsw


Yes, I figured my 2200w kettle would stress an inverter which is rated at 300w peak. At the moment I only see chargers for the laptop and tablet, and maybe a boombox being used, but I'm sure other things will creep onto the list. It's pretty cool the availability of warm white LED lamps now, especially in 12v. I will be able to have plenty of lighting in the tent run from a car battery. Won't even need the inverter most of the time.
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"robobass" wrote in message
...
On Friday, July 10, 2015 at 1:27:55 PM UTC+2, Jim Wilkins wrote:
"whit3rd" wrote in message
...
On Thursday, July 9, 2015 at 9:29:58 AM UTC-7, Jim Wilkins wrote:

[about odd AC measurements on a DC/AC inverter]

If you have a (possibly sacrificial) way to heat water with the
inverter you could time how long a measured amount of room
temperature
water takes to boil on the inverter and on Netzstrom. They should
be
pretty close to each other.


Bingo! An electric coffeemaker's brew time for a given water fill
is
a better RMS voltage meter than most inexpensive electronic
meters.


The heater's power draw would have to be within the capacity of the
inverter and battery, perhaps an immersion heater or single-serving
hot pot for a dorm room or office desk. A 1000W coffee maker would
pull over 80A from the 12V vehicle battery.

-jsw


Yes, I figured my 2200w kettle would stress an inverter which is rated
at 300w peak. At the moment I only see chargers for the laptop and
tablet, and maybe a boombox being used, but I'm sure other things will
creep onto the list. It's pretty cool the availability of warm white
LED lamps now, especially in 12v. I will be able to have plenty of
lighting in the tent run from a car battery. Won't even need the
inverter most of the time.

=======
I've measured substantial variation in the low voltage cutoff of my
inverters. One doesn't shut off at all, it will happily drain a 12V
battery to 7V. I tested it with a variable power supply, not by
ruining a battery. The others shut down somewhere between 10V and
11.5V.

I wouldn't run one off a car battery all night away from home because
they consume a fair amount of current internally and you might not be
able to start the engine in the morning.

-jsw


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I wouldn't run one off a car battery all night away from home because
they consume a fair amount of current internally and you might not be
able to start the engine in the morning.

-jsw


Right. I know mine is sucking power even when switched off. Where we're going I need to leave the car a fair distance from the tent and will be using a spare battery, mostly without the inverter attached. Still have to work out options for recharging in the morning...
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On 7/10/2015 6:19 AM, robobass wrote:

I wouldn't run one off a car battery all night away from home because
they consume a fair amount of current internally and you might not be
able to start the engine in the morning.

-jsw


Right. I know mine is sucking power even when switched off. Where we're going I need to leave the car a fair distance from the tent and will be using a spare battery, mostly without the inverter attached. Still have to work out options for recharging in the morning...

Back in the day, the whole idea of going "camping" is to get away from
all that stuff that uses electricity.
If you're not rubbing sticks together to start a fire, you ain't camping ;-)
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