Cheapest way to measure this?

I have to use a CPAP to sleep well. I'm going camping and will need to
bring battery power for the thing. So I would like to measure the
power draw over several nights to see what the highest power draw is.
The machine changes the air pressure depending on my particular needs
so I can't just plug it in and measure the current draw. I was
wondering if perhaps one of those cheap DSOs would be adequate. Any
advice?
Thanks,
Eric

 

[rickman]

etpm@whidbey.com wrote on 6/1/2017 11:44 AM:

I have to use a CPAP to sleep well. I'm going camping and will need to
bring battery power for the thing. So I would like to measure the
power draw over several nights to see what the highest power draw is.
The machine changes the air pressure depending on my particular needs
so I can't just plug it in and measure the current draw. I was
wondering if perhaps one of those cheap DSOs would be adequate. Any
advice?
Thanks,
Eric

You don't provide much info on how it will be powered from batteries. Does
the unit contain batteries? Will you be powering it by something like a UPS
that generates AC line power?

If you can use a measurement of AC line power, there are any number of
watt-hour meters available. They plug into an AC line socket and you plug
your device into them. A display shows the current voltage, current and
power. It accumulates the power to display energy in watt-hours.

If this is not good enough you will need to find a way to connect a
multimeter to the batteries to figure out the power draw. I'm not aware of
a universal solution for this. I have a small device that does the
watt-hour measurement for a USB connection, but is likely limited in power
and voltage.

--

Rick C

 

[George Herold]

On Thursday, June 1, 2017 at 11:38:35 AM UTC-4, et...@whidbey.com wrote:

I have to use a CPAP to sleep well. I'm going camping and will need to
bring battery power for the thing. So I would like to measure the
power draw over several nights to see what the highest power draw is.
The machine changes the air pressure depending on my particular needs
so I can't just plug it in and measure the current draw. I was
wondering if perhaps one of those cheap DSOs would be adequate. Any
advice?
Thanks,
Eric

Huh, fun. So you want to log data for ~8 hours.

(The cheapest way would be to find the max current draw and multiple by 8 hours.. or does the current vary widely?)

I've never used my DSO to log data to the computer. So no comment on that.

I've got a DMM with a data logger, I think I can set up the data rate.
I've only used that a few times.

A DMM with an RS-232 output wouldbe nice... send data to your computer.

With a little work you can DC couple into the sound card on your computer
and use that to record data.

Some Arduino thing maybe... Do you have an Arduino?

I've got a labjack, so I'd use that.
https://labjack.com/

Hey there's a USB data logger there... that might work for you.
https://labjack.com/products/digit

Or a cheap usb 'scope.

George H.

 

[Ralph Mowery]

In article <p3d0jc1pacfsfe6tim67n8a6ad7keumuka@4ax.com>,
etpm@whidbey.com says...

I have to use a CPAP to sleep well. I'm going camping and will need to
bring battery power for the thing. So I would like to measure the
power draw over several nights to see what the highest power draw is.
The machine changes the air pressure depending on my particular needs
so I can't just plug it in and measure the current draw. I was
wondering if perhaps one of those cheap DSOs would be adequate. Any
advice?
Thanks,
Eric

You did not mention what kind of power. If 120 volt AC, then one of the
Kill-o-Watt meters for under @ 20 will do this.

Here is another from Amazon of a different brand.

https://www.amazon.com/dp/B00E1E1XA2?psc=1

There are some less expensive ones from China on ebay without a case,
but by the time you get the plugs and case you will have a lot more in
it.

 

On Thu, 1 Jun 2017 12:28:18 -0400, rickman <gnuarm@gmail.com> wrote:

etpm@whidbey.com wrote on 6/1/2017 11:44 AM:
I have to use a CPAP to sleep well. I'm going camping and will need to
bring battery power for the thing. So I would like to measure the
power draw over several nights to see what the highest power draw is.
The machine changes the air pressure depending on my particular needs
so I can't just plug it in and measure the current draw. I was
wondering if perhaps one of those cheap DSOs would be adequate. Any
advice?
Thanks,
Eric

You don't provide much info on how it will be powered from batteries. Does
the unit contain batteries? Will you be powering it by something like a UPS
that generates AC line power?

If you can use a measurement of AC line power, there are any number of
watt-hour meters available. They plug into an AC line socket and you plug
your device into them. A display shows the current voltage, current and
power. It accumulates the power to display energy in watt-hours.

If this is not good enough you will need to find a way to connect a
multimeter to the batteries to figure out the power draw. I'm not aware of
a universal solution for this. I have a small device that does the
watt-hour measurement for a USB connection, but is likely limited in power
and voltage.

I should have said that the CPAP machine will run directly from a 12
volt battery. But since it also plugs into the wall I could use a watt
hour meter. I didn't even think of that. Thanks. Then whatever it
shows will be more than if run directly from a battery so that would
give me a little cushion.
Cheers,
Eric

 

On Thu, 1 Jun 2017 10:16:27 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

On Thursday, June 1, 2017 at 11:38:35 AM UTC-4, et...@whidbey.com wrote:
I have to use a CPAP to sleep well. I'm going camping and will need to
bring battery power for the thing. So I would like to measure the
power draw over several nights to see what the highest power draw is.
The machine changes the air pressure depending on my particular needs
so I can't just plug it in and measure the current draw. I was
wondering if perhaps one of those cheap DSOs would be adequate. Any
advice?
Thanks,
Eric

Huh, fun. So you want to log data for ~8 hours.

(The cheapest way would be to find the max current draw and multiple by 8 hours.. or does the current vary widely?)

I've never used my DSO to log data to the computer. So no comment on that.

I've got a DMM with a data logger, I think I can set up the data rate.
I've only used that a few times.

A DMM with an RS-232 output wouldbe nice... send data to your computer.

With a little work you can DC couple into the sound card on your computer
and use that to record data.

Some Arduino thing maybe... Do you have an Arduino?

I've got a labjack, so I'd use that.
https://labjack.com/

Hey there's a USB data logger there... that might work for you.
https://labjack.com/products/digit

Or a cheap usb 'scope.

George H.

Greetings George,
I do have an Arduino. Rickman suggested using a watthour meter. I
think that might be the best way because it will give me result that
is higher than if I run the thing directly from a battery since the
power supply uses some power.
Thanks,
Eric

 

On Thu, 1 Jun 2017 14:02:47 -0400, Ralph Mowery
<rmowery28146@earthlink.net> wrote:

In article <p3d0jc1pacfsfe6tim67n8a6ad7keumuka@4ax.com>,
etpm@whidbey.com says...

I have to use a CPAP to sleep well. I'm going camping and will need to
bring battery power for the thing. So I would like to measure the
power draw over several nights to see what the highest power draw is.
The machine changes the air pressure depending on my particular needs
so I can't just plug it in and measure the current draw. I was
wondering if perhaps one of those cheap DSOs would be adequate. Any
advice?
Thanks,
Eric

You did not mention what kind of power. If 120 volt AC, then one of the
Kill-o-Watt meters for under @ 20 will do this.

Here is another from Amazon of a different brand.

https://www.amazon.com/dp/B00E1E1XA2?psc=1

There are some less expensive ones from China on ebay without a case,
but by the time you get the plugs and case you will have a lot more in
it.

Well, that was simple. I have a Kill-A-Watt ordered and on its way.
Thanks everybody for your advice. Now I need to look for some good
deals on LiIon batteries. Maybe a solar charger too.
Eric

 

[Martin Riddle]

On Thu, 01 Jun 2017 14:14:42 -0700, etpm@whidbey.com wrote:

On Thu, 1 Jun 2017 14:02:47 -0400, Ralph Mowery
rmowery28146@earthlink.net> wrote:

In article <p3d0jc1pacfsfe6tim67n8a6ad7keumuka@4ax.com>,
etpm@whidbey.com says...

I have to use a CPAP to sleep well. I'm going camping and will need to
bring battery power for the thing. So I would like to measure the
power draw over several nights to see what the highest power draw is.
The machine changes the air pressure depending on my particular needs
so I can't just plug it in and measure the current draw. I was
wondering if perhaps one of those cheap DSOs would be adequate. Any
advice?
Thanks,
Eric

You did not mention what kind of power. If 120 volt AC, then one of the
Kill-o-Watt meters for under @ 20 will do this.

Here is another from Amazon of a different brand.

https://www.amazon.com/dp/B00E1E1XA2?psc=1

There are some less expensive ones from China on ebay without a case,
but by the time you get the plugs and case you will have a lot more in
it.

Well, that was simple. I have a Kill-A-Watt ordered and on its way.
Thanks everybody for your advice. Now I need to look for some good
deals on LiIon batteries. Maybe a solar charger too.
Eric

If you looking for batteries for extended laptop use check out these
guys:
<http://www.bixpower.com/product-p/bat-cp170-s10.htm>
It even says it might run a CPAP for 2-3 nights.

LiIons are expensive but it might be what your looking for. I'd
forget about the solar charging, the panels would be huge.

Cheers

 

On Thu, 01 Jun 2017 14:14:42 -0700, et...@whidbey.com wrote:

On Thu, 1 Jun 2017 14:02:47 -0400, Ralph Mowery
rmower...@earthlink.net> wrote:

In article <p3d0jc1pacfsfe6tim67n8a6ad7keumuka@4ax.com>,
et...@whidbey.com says...

I have to use a CPAP to sleep well. I'm going camping and will need to
bring battery power for the thing. So I would like to measure the
power draw over several nights to see what the highest power draw is.
The machine changes the air pressure depending on my particular needs
so I can't just plug it in and measure the current draw. I was
wondering if perhaps one of those cheap DSOs would be adequate. Any
advice?
Thanks,
Eric

You did not mention what kind of power. If 120 volt AC, then one of the
Kill-o-Watt meters for under @ 20 will do this.

Here is another from Amazon of a different brand.

https://www.amazon.com/dp/B00E1E1XA2?psc=1

There are some less expensive ones from China on ebay without a case,
but by the time you get the plugs and case you will have a lot more in
it.

Well, that was simple. I have a Kill-A-Watt ordered and on its way.
Thanks everybody for your advice. Now I need to look for some good
deals on LiIon batteries. Maybe a solar charger too.

As a matter of fact, I didn't know anyone still used CPAC machines. I thought I saw a commercial for something called a "CPAP mouthpiece"