Dmm with simultaneous voltage and current measurament?

[mikeselectricstuff]

Just been doing the four DMM thing yet again for testing a DC/DC converter, and it struck me that all it would take for a standard DMM to be able to measure simultaneous(ish) voltage and current would be a multiplexer to alternately measure the input voltage and the voltage across the shunt -then it's just firmware to display wattage.
Anyone seen a DMM that can do this?

[cybergibbons]

UT-71E does this http://www.uni-trend.com/UT71E.html

And the Gossen Metrahit Energy as well http://www.gossenmetrawatt.com/english/produkte/metrahitenergy.htm

[mikeselectricstuff]

AFAICS that only does AC power, using an external adapter

.. and I bet none let you plug 2 together to show efficiency....

[Kiriakos-GR]

AFAICS that only does AC power

True, the page 69 indicates that ...

And so get ready to pay the high price for the Gossen Metrahit .

As I did , so to buy an true AC/DC amperes clamp by chauvin-arnoux .

[NiHaoMike]

It should be relatively easy to build a meter that can measure both current and voltage at the same time. Just an analog front end, two ADCs, and a microcontroller.

[allanw]

Most meters only have a common ground terminal. For a combined voltage/current measurement to be useful in all situations, they'd need a separate terminal for current - side. I've never seen those on a meter before.

edit: Nevermind, a common return terminal is still useful for measuring power.

[mikeselectricstuff]

exactly - the way the terminals are typically arranged, power goes in the current socket and out of COM, and the voltage socket goes to the other side of the supply. OK you may have a wrong sign but that's no big deal.
Obviously it's not hard to build something, altough by the time you've covered a decent range of voltage/current and added user interface etc. it becomes a bit of a PITA for an occasional requirement
It's just annoying that pretty much all DMMs have 99% of the hardware functionality already there to halve the number of meters required...

[Kiriakos-GR]

Well by getting my pile of those old Fluke bench type DMM  ( X 3 ), some people would consider it as crazy move.

But now I can combine them to measure  input voltage - output voltage + Amperes.

I bet that this simple way its the most practical one , and almost at the most logical cost, for devices with good accuracy.

Or else with 15 dollars get an analog voltmeter and an analog amperes meter , and build your own simple power meter .
  

[PetrosA]

They make them for guys like me, but probably not for guys like you

This is about the cheapest I can find:

http://www.tequipment.net/Protek667C.html

Then this one:

http://www.tequipment.net/Extech382075.asp

Then there are the big boy toys:

http://www.tequipment.net//Hioki3196.html

http://www.tequipment.net/FlukePowerQuality435MO.html

[Feanor]

It's called a watt meter and they are readily available.

Here is another link: -

http://www.valuetesters.com/Clamp-On-Power-Meter.php

I like the clamp on type, it means you do not have to rearrange your circuit to measure the power. They are expensive though.

On eBay there are some cheap ones, but they are not clamp on and have poor resolution. But that i fine in some applications. Guess you get what you pay for.

http://cgi.ebay.com/GTP-130-High-precision-watt-meter-and-power-analyzer-/260670362063?pt=Radio_Control_Parts_Accessories&hash=item3cb12a11cf

[EEVblog]

Just been doing the four DMM thing yet again for testing a DC/DC converter, and it struck me that all it would take for a standard DMM to be able to measure simultaneous(ish) voltage and current would be a multiplexer to alternately measure the input voltage and the voltage across the shunt -then it's just firmware to display wattage.
Anyone seen a DMM that can do this?

Yes, the Gossen Metrahit Energy.
I have one for review and must say that it's pretty awesome!
It's the meter I'd keep if I had to have only ONE meter.

Dave.

[PetrosA]

Yes, the Gossen Metrahit Energy.
I have one for review and must say that it's pretty awesome!
It's the meter I'd keep if I had to have only ONE meter.

Dave.

Yeah Dave, just keep RUBBING IT IN!

[EEVblog]

Yeah Dave, just keep RUBBING IT IN!

Ok, people send me stuff for free, it's not a bad perk!

If it's any consolation, now I have so many meters it's almost like "not another bloody meter"!

Actually, I've just been offered a Rigol for free to give away on the forum! More details soon I'm sure.

Dave.

[Simon]

Yeah Dave, just keep RUBBING IT IN!

Ok, people send me stuff for free, it's not a bad perk!

If it's any consolation, now I have so many meters it's almost like "not another bloody meter"!

Actually, I've just been offered a Rigol for free to give away on the forum! More details soon I'm sure.

Dave.

now that's more like it... which model ?

[Mechatrommer]

Actually, I've just been offered a Rigol for free to give away on the forum! More details soon I'm sure.

me! me! me!
about the Gossen, it seems a difficult task for me to get one online.

[djsb]

You have to go direct to the nearest distributor or Farnell/element whatever does them.

[jahonen]

Linear Technology has LT2940 for high-side (6-80V) analog power monitoring. That could be used if accuracy requirements are not steep.

Regards,
Janne

[Simon]

wanting to get into controlling displays with pic's I was actually thinking of designing a power monitor so as to have something to display, it should be relatively easy to setup for voltage and current measuring and then work out the power. A 16F type pic could probably monitor 2-4 channels depending on how much hardware your willing to throw at it (mainly high side current sensing chips that don't cone cheap from maxim but are some of the best)

[Pedro]

Well, the Fluke 45 bench meter has exactly that. It has a 'dual' mode in which it shows both current and voltage measurements. It halves the sample rate, but you can have the two readings simultaneously.

[Howardlong]

Sorry to bring up a really old thread, but is there anything out there that's reasonably priced and portable that does both DC voltage and current simultaneously yet, preferably with a PC interface, or  data logging?

It does seem to be a bit of a gap in the market. I can't justify blowing half a grand for a meter I'd use very rarely, when a bit of spreadsheet juggling with two separate sources would work just as well albeit slightly less conveniently.

[gdewitte]

Mooshimeter? https://moosh.im/mooshimeter/

[Howardlong]

Mooshimeter? https://moosh.im/mooshimeter/

Hmm, looks worth a punt, just ordered one.

Thank you!

[jwm_]

Are you requirements fairly low voltage and don't need extreme accuracy? theese dohickies work over an okay voltage range and can probably be easily modified to extend it with external power.

http://www.ebay.com/itm/LCD-USB-Charger-Battery-Capacity-Power-Current-Voltage-Tester-Meter-White-NEW-/281534599237?pt=LH_DefaultDomain_0&hash=item418cc51045

I used them on either end of a DC-DC converter module for rough estimates of how it was doing with no issues.

linear has some great chips that do this too with high accuracy if you want to roll your own.

    John