Dmm with simultaneous voltage and current measurament? - Page 1
Forum section: electronics / general

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 24, 2010, 10:38:57 pm
content: 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?

author: cybergibbons
author_rank: Frequent Contributor
timestamp: October 24, 2010, 10:54:00 pm
content: UT-71E does thishttp://www.uni-trend.com/UT71E.htmlAnd the Gossen Metrahit Energy as wellhttp://www.gossenmetrawatt.com/english/produkte/metrahitenergy.htm

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 24, 2010, 11:24:11 pm
content: AFAICS that only does AC power, using an external adapter.. and I bet none let you plug 2 together to show efficiency....

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: October 24, 2010, 11:35:58 pm
content: Quote from: mikeselectricstuff on October 24, 2010, 11:24:11 pmTrue, 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 .

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 25, 2010, 03:11:21 am
content: 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.

author: allanw
author_rank: Frequent Contributor
timestamp: October 25, 2010, 08:15:03 am
content: 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.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 25, 2010, 11:06:50 pm
content: 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 requirementIt's just annoying that pretty much all DMMs have 99% of the hardware functionality already there to halve the number of meters required...

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: October 25, 2010, 11:44:26 pm
content: 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 .

author: PetrosA
author_rank: Frequent Contributor
timestamp: October 26, 2010, 02:31:08 am
content: They make them for guys like me, but probably not for guys like youThis is about the cheapest I can find:http://www.tequipment.net/Protek667C.htmlThen this one:http://www.tequipment.net/Extech382075.aspThen there are the big boy toys:http://www.tequipment.net//Hioki3196.htmlhttp://www.tequipment.net/FlukePowerQuality435MO.html

author: Feanor
author_rank: Regular Contributor
timestamp: October 26, 2010, 05:33:09 am
content: It's called a watt meter and they are readily available.Here is another link: -http://www.valuetesters.com/Clamp-On-Power-Meter.phpI 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

author: EEVblog
author_rank: Unknown
timestamp: October 29, 2010, 09:53:57 pm
content: Quote from: mikeselectricstuff on October 24, 2010, 10:38:57 pmYes, 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.

author: PetrosA
author_rank: Frequent Contributor
timestamp: October 29, 2010, 11:50:16 pm
content: Quote from: EEVblog on October 29, 2010, 09:53:57 pmYeah Dave, just keep RUBBING IT IN!

author: EEVblog
author_rank: Unknown
timestamp: October 30, 2010, 12:30:05 am
content: Quote from: PetrosA on October 29, 2010, 11:50:16 pmOk, 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.

author: Simon
author_rank: Unknown
timestamp: October 30, 2010, 09:43:32 am
content: Quote from: EEVblog on October 30, 2010, 12:30:05 amnow that's more like it... which model ?

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 30, 2010, 10:24:38 am
content: Quote from: EEVblog on October 30, 2010, 12:30:05 amme! me! me!about the Gossen, it seems a difficult task for me to get one online.

author: djsb
author_rank: Super Contributor
timestamp: October 30, 2010, 02:10:38 pm
content: You have to go direct to the nearest distributor or Farnell/element whatever does them.

author: jahonen
author_rank: Super Contributor
timestamp: October 30, 2010, 02:22:51 pm
content: Linear Technology hasLT2940for high-side (6-80V) analog power monitoring. That could be used if accuracy requirements are not steep.Regards,Janne

author: Simon
author_rank: Unknown
timestamp: October 30, 2010, 02:32:45 pm
content: 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)

author: Pedro
author_rank: Newbie
timestamp: October 30, 2010, 07:44:18 pm
content: 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.

author: Howardlong
author_rank: Super Contributor
timestamp: February 23, 2015, 03:11:47 pm
content: 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.

author: gdewitte
author_rank: Unknown
timestamp: February 23, 2015, 03:14:45 pm
content: Mooshimeter?https://moosh.im/mooshimeter/

author: Howardlong
author_rank: Super Contributor
timestamp: February 23, 2015, 08:13:40 pm
content: Quote from: gdewitte on February 23, 2015, 03:14:45 pmHmm, looks worth a punt, just ordered one.Thank you!

author: jwm_
author_rank: Frequent Contributor
timestamp: February 23, 2015, 08:34:49 pm
content: 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=item418cc51045I 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