Hardwire multimeter

[retireddiy]

Hello all, a curious question. Can a multimeter be hardwired to a wall wort for its dc power, with proper dcv and amps? I have a couple of digital and analog meters to use if it would work. All have 10 amp capability.

 

[kbeefy]

I can't think of any reason it wouldn't. Just match the power supply to the battery voltage in the multimeter.

 

[LopezBart]

You may need cleaner power than you get from a wall wart for the digital ones, but it might well work ok.

 

[LXCam]

Hello all, a curious question. Can a multimeter be hardwired to a wall wort for its dc power, with proper dcv and amps? I have a couple of digital and analog meters to use if it would work. All have 10 amp capability.

Whatta a wall wort?

Edit: neber mind, I wiggered it wout after wooking it wup

 

[CoogarXR]

if you are trying to rig a permanent reading of some sort, make sure you are using a meter with a mechanical on/off. I know many of my soft-on meters will turn themselves off after a while. Cheaper meters that just power on when you turn the knob will stay on as long as the battery lasts.

 

[retireddiy]

Thanks, I’ve never found anything online, or I never typed the right question. My plan is to use 2 different meters for my variac enclosure I’m making.

 

[no704]

Kill a watt?

 

[DHCrocks]

you can get panel meters to monitor the voltage/amps. They are super cheap and small so easy to rig up. It'll look a whole lot better then a couple of meters hanging off to the side.

 

[Zeke]

Look at this variac. It has everything in one cabinet. I tried to edit so it starts at 7:32 but it won't copy to here. So go to 7:32 to see the variac.
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[DGersic]

Thanks, I’ve never found anything online, or I never typed the right question. My plan is to use 2 different meters for my variac enclosure I’m making.

I have a half dozen panel meters mounted above my test bench to check the outputs of a power supply board.

 

[retireddiy]

Thanks, my choice is simple to me. I have acquired various multi meters of good quality and no need for hacks to have a panel meter perform like I would like. I'm not concerned with looks just abilities. I respect your opinions completely.

 

[dogdog]

Thanks, I’ve never found anything online, or I never typed the right question. My plan is to use 2 different meters for my variac enclosure I’m making.

eBay have plenty of these digital display to read ac or dc and amps. Why try to reinvent a wheel

Something like these for about $20 ish used to be cheaper…

Proper shunt for dc amp or hall sensor for ac amp

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[Tundra1]

I would be concerned about isolation of the dmm leads from any wall wart feeding the 9v battery lugs. The meter design assumes the 9v battery is floating and would likely not provide much additional separation of leads from power source.

 

[dave*99]

I would be concerned about isolation of the dmm leads from any wall wart feeding the 9v battery lugs. The meter design assumes the 9v battery is floating and would likely not provide much additional separation of leads from power source.

^ This is generally true. And you may not know you have an issue until the wall wart starts smoking.

30 years ago I even had this problem with some panel meters. I tried to run several of them from a single power supply, all in one chassis. Any meters that were measuring current ended up each needing their own isolated supply. Turns out the negative of the meter power input is connected to the common measurement terminal.

Also, for bench testing current measurements, I prefer to measure current with a shunt. Running the DUT current through the DMM while I'm poking around on the DUT inevitable results in blowing the fuse in the DMM. Some of those fuses are expensive and specialized.

 

[Max]

I would be concerned about isolation of the dmm leads from any wall wart feeding the 9v battery lugs. The meter design assumes the 9v battery is floating and would likely not provide much additional separation of leads from power source.

Agreed. Even worse as almost all wall warts these days will be switching with no internal transformer isolation. As noted previously, panel meters are a good option, as is a kill-a-watt. I used analog meters on my variac to avoid any kind of issues. Good sources of relatively inexpensive panel meters (both digital and analog) are Marlin P. Jones Electronics and The Electronic Goldmine. Of course, places like Mouser and Digikey also have them as well.

 

[retireddiy]

Great suggestions thank you. My next thought, take the wall wort out of the picture and attach 14 awg wires to output side. Install banana jack connectors into enclosure and connect multimeter to them.

 

[Chukster]

Whatta a wall wort?

Edit: neber mind, I wiggered it wout after wooking it wup

A wall wart be a child of the devil, a low-cost (not necessarily low-price) contrivance, cost reduced to the barest minimum of components, sourced from the lowest bidder. A commodity product of generally dubious quality and reliability. Often made with a simple co-axial DC power plug which is NOT captured by the device it powers, but can fall out easily, leaving the device unpowered and the technician in a state of panic because that thing they are supposed to fix has suddenly gone darker than a well-digger's grave.

For my money the fact that so much of our current infrastructure (esp IT) is powered by these evil turds is just catastrophe waiting in the wings.

A google assignment for the students: 'Value Engineering' , 'Cost reduced', and especially 'Madman Muntz'

 

[retireddiy]

Have mercy, thus endeth the lesson.

 

[DGersic]

A wall wart be a child of the devil, a low-cost (not necessarily low-price) contrivance, cost reduced to the barest minimum of components, sourced from the lowest bidder. A commodity product of generally dubious quality and reliability. Often made with a simple co-axial DC power plug which is NOT captured by the device it powers, but can fall out easily, leaving the device unpowered and the technician in a state of panic because that thing they are supposed to fix has suddenly gone darker than a well-digger's grave.

For my money the fact that so much of our current infrastructure (esp IT) is powered by these evil turds is just catastrophe waiting in the wings.

A google assignment for the students: 'Value Engineering' , 'Cost reduced', and especially 'Madman Muntz'

You forgot its most endearing physical aspect. Being a single plug device that is two plugs wide, and has the cable oriented to block anything else from being below it. Bonus points for polarized plug blades used to further increase Its footprint.

 

[LXCam]

A wall wart be a child of the devil, a low-cost (not necessarily low-price) contrivance, cost reduced to the barest minimum of components, sourced from the lowest bidder. A commodity product of generally dubious quality and reliability. Often made with a simple co-axial DC power plug which is NOT captured by the device it powers, but can fall out easily, leaving the device unpowered and the technician in a state of panic because that thing they are supposed to fix has suddenly gone darker than a well-digger's grave.

For my money the fact that so much of our current infrastructure (esp IT) is powered by these evil turds is just catastrophe waiting in the wings.

A google assignment for the students: 'Value Engineering' , 'Cost reduced', and especially 'Madman Muntz'

My gawd man, I had no idea such evil existed in this world.


I just figured the OP had a lisp.

 

[retireddiy]

lol

 

[Chukster]

My gawd man, I had no idea such evil existed in this world.


I just figured the OP had a lisp.

It does. I'll give 'power bricks' some leeway, as they are often whole switchmode power supplies, in the middle of the cable, performing the conversion from 120VAC down to other usable voltages. But straight bulky wall-warts? Pahh!! A bulky heat-producing transformer, in a cheap case, cheap connections to the outlet, generally poor regulation, (well, yeah, the product does handle voltage regulation internally), nah, not a fan of that type. For all the reasons already listed.