Found a DIY multimeter: tell me about it

[Cart]

Was at some thrift stores picking up too many usb variety cables and power adapters of various kinds and other gizmos and gadgets.

One of them was a DIY multimeter which I want to learn more about. I think it's pretty cool when someone puts their time into something like this and I'd like to be able to make things of some interest as well at some point. Figured at worst I could use the lcd, potentiators , switches, fan, casing even and perhaps get an idea or two. So I haggled it down from $30 to $10 and did some tests:
(Tested using same leads/new batteries)

DIY Multimeter Etekcity

"Sense" (Adjusting current does nothing)
Internal:
USB connected to computer: (V drops A rises, W rises then drops)
External-Manual: Internal-Manual: DCV
AA- 1.625V 1.389V N/A-W&A AA- 1.58V
9V- 6.953V (sense neg too neg) 8.533V N/A-W&A 9V- 9.05V
External-Auto: Internal-Auto:
AA- 1.636V .091V 3.179A .288W
9V- 6.356V .024V 1.326A .346W

"Load"
Internal: ~~
External: ~~



questions/observations:
- not sure what current adjustments are for or how to test it's functionality
- large heatsinks and 2 fans on bottom - not sure what usb function is for, does not power on multimeter, though does change "internal" voltage (perhaps broke)
- way to test usb ports for power in some way? would there be any point to this?
- not sure what sweep is
- afraid to test above 9v as reader indicates 9.999 max read.
- not sure what current adjustments are for
- never done a load test other than on a car some time ago, though that is generally beyond 9.999V. suggestions on how to test load quickly and to see if this has any accuracy in that regard
- unstable measurements relative to Elek
- lcd "lights up" when i first turn it on then it loses it's backlight (observational note)

- measures Volts, Watts, Amps
- has manual and auto mode, though not sure what differentiates them beyond internal readings
- the internal readings look like AC readings sometimes

(I was drunk at the time of this posting.... apologies for any oddities(including not taking a close look at the USB soldering before closing it up...))

-James

 

[73's de Edd]

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Sir Cart . . . . . . .

Muiltimeter . . . .multimeter ?. . . . au contraire . . .seems like what you actually have there is a power supply with its power output being the two Load terminals to the right. Then you use the coarse and fine voltage adjustments to trim in your desired output voltage.
The Sense would be for routing its wiring connection RIGHT up to the load connection for compensatory voltage sensing.
If you had a long wire run between the power unit and the final load pulled HIGH current, there would be voltage loss in the interconnecting wiring resistance.
With the sense line connected, it would detect that loss and auto bump up the adjustment of the PS output voltage to compensate for it.
(You shore gots a lot there . . .for yer munney (10 Bux) . . . . . but , its external cosmetics could certainly be "dressed up" a bit.)


73's de Edd



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[Cart]

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Sir Cart . . . . . . .

Muiltimeter . . . .multimeter ?. . . . au contraire . . .seems like what you actually have there is a power supply with its power output being the two Load terminals to the right. Then you use the coarse and fine voltage adjustments to trim in your desired output voltage.
The Sense would be for routing its wiring connection RIGHT up to the load connection for compensatory voltage sensing.
If you had a long wire run between the power unit and the final load pulled HIGH current, there would be voltage loss in the interconnecting wiring resistance.
With the sense line connected, it would detect that loss and auto bump up the adjustment of the PS output voltage to compensate for it.

.

Thank your for the correction and insight.
After watching a few videos on DC power supplies and reading a number of articles and how to's and the like. I still can't for the life of me understand how i get this to work or if it even does work.

I only have leads from the Etekcity multimeter i have so i haven't hooked up both load and sense wires. The LCD informs me that there "is no source detected" and i can only guess that is due to not having sense hooked up.
Though I have tried simple tests to simply light up an led from the load and adjusting the current and flipping various settings to no avail. Used multimeter and plugged it into the load outputs and got no readings either on DCV (0.00V). When i adjust the current the voltage readings up top do not change which i assume they would like other power supplies out there where you can just set the voltage to X and go on from there.

If i were to get more leads to have the sense and load working in conjunction (on the assumption he programmed it to not output anything unless "a source is detected") which leads would be best for this case? Ones with clips or x,y,z.

Also, if there is some other test to demonstrate that this is malfunctioning, please do tell me how to find that out.

Figured i'd at least be able to light up and led using the load outputs....

Thanks,
James