i would have fitted an anoluge ammeter but i`m old school i would if it was me also i would be checking with a good quality DMM check voltage out from time to time as they can be very untrue at times,and the ammeters are not really much better… but for show purposes there really a great look…glad you got it figured out…still i would be contacting *silicon chip…*getting their data because it covers many facets of those switch mode supply’s…bumping current as well from mem…but not 100% …but over about 4-6 articals etc…i have them here somewhere but i dont remember what year they were issued out …100-1000 amp
D.C. meters are not hard to find really…depends where you look…but that is a nice unit by look of it…
potentially you have a very high current/voltage being lead straight into your board,it could be quite leatrhal if there was a leak or short or other electrical fault…
This is the diagram there are a couple other variations I tried including both positives to to the load positive and connecting the negative for the meter to the load negative (tried both sides of the shunt).
I wired the + & - for the meter to the psu side.
The wire to load is 4mm automotive copper wire. It’s clean.
That shunt is 100amp. Don’t think you will find an internal 12v meter in such a compact size like that.
That’s a good point, although it depends on the maximum output power that you’ll need, there may be something available. As Bob said, these meters can be quite difficult to work with when not used in appropriate setups. Have you been able to verify it against another ammeter to ensure that the results you are getting are accurate?
Using my uni-t DMM and it’s reading 1.6amps. Which is what I was expecting.
I have adjusted the tolerance on the back but it’s made no improvement.
I used the shunt setup because I had it laying around and also because most of those internal meters are only rated to 10amp. I was expecting a flat battery could initially pull more than that and I don’t feel to replacing stuff all the time.
That’s a good point, the rating isn’t that high so using a shunt in order to allow for current to bypass definitely sounds like a good idea. Do you have any other shunts with a different resistance that you can replace it with to see how it affects the value that is read? It should be an ohmic system, so I’d expect direct proportionality, I’m curious to see how the value changes.
No I don’t. Given that this is top of the range Chinese junk, it could just be the unit. Could just be me too if I’m being fair but looking at schematics and other vids I can’t see any issues.
The only thing I can think of is perhaps cutting the brass blacks has altered the reading and I should have tested prior to modifying. O well. I don’t want to order another one but I also don’t want to hook up to a battery unless I know what it’s doing. Knowing the volts is a start.
That’s an excellent point, but that shouldn’t cause the error to be that significant, I agree with Bob and Brian that the best option in this situation may be to use an analog meter to remove the uncertainty of where the issues are occurring as mechanically they’re much simpler. If there’s anything else that you need please let us know.
Mat. That circuit should work. As I mentioned the wire etc resistance between shunt and negative MUST be as close to zero as possible.
uni-t is a good instrument. My multimeter of choice. Clamp meter is good too, will read milliamps.
What have you attempted to adjust here??? If it is the calibration pots in the meter unless you have a Fluke Calibrator or something similar laying around your work bench you can confine that unit to the scrap heap or send it out to a cal lab for re-calibration.
Mat, YOU MUST USE THE SHUNT THAT CAME WITH THE METER. Not one you “just happened to have laying around”. Shunts are rated in a couple of ways, Max current (Amps) which is a function of physical size and power handling capability and usually “millivolts per Amp” which is a function of resistance and tells the user how many millivolts voltage drop per amp will appear across the shunt. The amp meter then is basically a voltmeter which measures this and the correct value in Amps is calculated for display. Shunts vary widely in both of these specs so if you have picked up any old shunt the results could be anything.
Analog meters. Most of the common very affordable units will be a basic 1 mA fsd (full scale deflection) and a shunt is used to bypass most of the current leaving just enough available to drive the meter. Thus if you have a meter with a dial 0 to 10 Amps you would have a shunt which at 10 Amps would bypass 9999 mA and pass 1 mA through the meter for fsd. Shunts could be external or internal. Internal is easier as you just buy a 5A, 10A or whatever meter.
Current (or Volt) meters are rated Full Scale Deflection They mostly will take a bit more but will not read it. By the way, tolerances are usually stated as a % of fsd NOT the value you are reading.
As previously stated Hall effect devices do not need a shunt and the voltage drop is usually in the order of a couple of millivolts under all conditions and can probably be ignored in all but the most critical applications.
Is there any way you can get the make and model of the meter you are using and we can maybe find out a bit more about it. Although if Chinese I wouldn’t hold my breath.
Cheers Bob
If I purchase this unit, do you think it would have the same issues? I’m avoiding mechanical as I want small and compact and I can get volts and amps on the same display.
Mat
Core are confusing the issue here I think.
Just checked that link. Suggested wiring diagrams indicate an external shunt for the current (Amps) measuring function. If this is the case you MUST use the shunt supplied with the meter as I said previously.
However the text that describes this device states that a shunt is not required.
Could Core please clarify this and amend the documentation.
Little wonder confusion reigns supreme. If I were you I would do no more until this issue is cleared up.
Comparing the suggested circuits with the one you posted this looks to be pretty much the same as what you already have.
It may be that the shunt is indeed internal and is shown on the diagrams as a way of illustrating the operation.
Wiring option 2 would be your simplest for you. Where a battery is shown this would be your PSU and the device under test (DUT) would be your lamp strip.
If it is internal shunt just leave it out and connect yellow to earthy or negative side of load (or DUT) and black (common) to supply negative.
You need to get CLARIFICATION OF THIS SHUNT SITUATION before you go any further.
Cheers Bob
Mat
Follow on. Just revisited your circuit you posted. Sorry to have misled you, that would probably not work. If you compare that to Wiring option 2 in that link you will see why. Yellow and Red wire from the meter should be reversed and thin red wire from the meter connects to supply positive with the thick red wire. Thin black not connected.
Are you powering the meter separately as shown or from the PSU?
Cheers Bob
Hey guys, thanks for bringing this to attention will take a look and clarify the situation here.
EDIT: So took a look at the Volt/Current meter in question and it seems that this specific model does in fact have the shunt built in. The diagrams are common across the models that the manufacturer produces. Hopefully this helps!
It does state it has an internal shunt and rated to 10amp. It also states if continuous load over 5amps use a shunt. Doe you guys sell the shunts for this unit?
Would be more help if this was stated. Designed to create confusion to the uninitiated. Typical Chinese.
A shunt would be used to extend the range. I don’t think this would work if trying to extend a 10A unit. I think you would have to use a higher fsd unit which is designed for an external shunt. If the 10A unit does not require a shunt it may use a hall effect device so because this is not resistive you could not calculate a shunt value to accurately extend this type of sensor.
Mat
The blurb does not state this. It says if over 5A continuous to solder the joints. Probably to prevent a mechanical joint overheating which tends to have a run away effect, the hotter it gets the worse it gets.
If Mitchell is correct (and I have no reason to think not) just wire it up without the shunt as you are only powering a light strip at the moment the likelihood of more than 10 A is small. Concentrate on getting the Amp meter and Volt meter to approximate your multimeter for now and worry about more current later. You are trying to do too much at once and getting confused.
Apologies for any confusion, we typically grab the descriptions from our supplier, on occasion, there are products that need to be cleared up. I will make sure that someone adds this soon!
As you have said, it may be worth getting a 0-50A meter if you are working with higher currents:
Mitchell
That type of meter is a lot more use and simpler. The measuring circuit being isolated is much more flexible. If the low side of the load really needs to be at negative volts or ground the meter could be used in the high side of the circuit.
Mat
Being isolated this meter is much easier to use. Note the shunt comes with the meter.
Be aware that the unit MUST BE POWERED BY A SEPARATE SUPPLY. as the negatives are not shared. This should enable it to be used in the positive side of the load if required.
This supply could be simply an 18650 LiPo with a 5V boost converter but it MUST be isolated from the primary supply.
Cheers Bob
Edit.
Mat note how this shunt is specified. 50A/75mV which the voltage across it is 75mV at current of 50A. Thus resistance of 0.0015 ohm. you can see that any added resistance in this loop due to maybe thin wire or poor connection (not soldered) will have a great effect on the accuracy of the device.
Cheers Bob
I don’t see how wiring an volt/amp meter is confusing but perhaps just misunderstanding occurs because of messaging.
That meter is only good for 10amp as is but shows it can be wired to a shunt. Hence my question of whether the could supply same. 10amps is no good to me as it will fry.
And as stated in initial post this will be used to charge batteries. Not run leds. The leds just happened to be the easiest load I could find laying around to test with.
Mat
I think you misunderstand. The 10 Amp model does not use a shunt. The shunts depicted in the diagrams are for different models of meter with a higher current capability. Confusing I know but Mitchell just clarified that. If required the shunt is supplied with the meter and must be the one used. Refer the edit for my previous post.
Cheers Bob
10 Amps. That means each cell charging at 2.5 Amps. Don’t know what max is for average 18650 but that must go pretty close.
Cheers Bob
Mat
Just having a look at a LiPo I have here. 2600 mAhr. There is some info printed on pack. I quote
Charging current 0.5C maximum = 1.3 Amp
Advised charging 0.2C = 520 mA
On that basis you should be looking at a max of 5.2 Amp. I think much more and something may be in trouble.
These things weren’t around when I stopped full time work and unfortunately I have not kept up with the fine details of the different battery chemistries. I do know that for battery longevity there are specific charge / discharge protocols one should follow. I don’t know if the battery will look after max currents etc itself or not but I have a feeling there is some sort of charge controller in use. Another battery management system looks after cell balancing I believe.
All things being normal I believe you should get nowhere 10 Amps but maybe I am wrong. I don’t know.
Cheers Bob
