100V 10A DSN-VC288 DC Voltmeter Ammeter Review – calibration problems

[Kiriakos GR]

Today I do feel as an idiot for spending my four valuable Euro coins about buying these two 100V 10A DSN-VC288 panel meters.

I did break my oath of not buying cheap products because I am a poor man and it is not wise for us poor people to experiment with solution them never really deliver what they supposed to deliver.

But thanks to donation which ITTSB Blog received by a new forum member, I thought to invest portion of that money for acquiring another one opportunity for production of valuable content.
This be in benefit of all members of ITTSB forum, among to thousands young ones, them exploring world of electronics.

Last year I got a step-up voltage converter, input 9~24V DC and output this is up to 60V.
And I am about to add this PCB in to enclosure, and to add two panel meters one at input and a second in the output, and also one 10 turn’s potentiometer will deliver more precision speaking of voltage adjustment.
The all idea this is me to create one voltage source for mostly powering electrolytic capacitors at their higher working voltage, for evaluation of their condition.

100V - 10A, DSN-VC288 DC Voltmeter Ammeter which I received them both demonstrated huge error as ammeters right away.

I thought to use calibration pot for current adjustment, but I discover that pots were all ready at lowest setting and it was impossible them to help at lowering down the measured value.

Theoretical specifications’ of Voltage Error Range: ± 0.1% & Current Error Range: ± 1%
These are both a bad joke, especially for Current range.

Bellow there is three screen shots DSN-VC288 side by side with U1272A and how comparable are the measurements’ of this questionable in quality DSN-VC288.
In order my tests them to be unquestionably correct I use two car light bulbs as load (Head lights) power consumption of 4.5A at 15V its one.

As you can see DSN-VC288 at default condition this is terrible as Ammeter.
Power source for DSN-VC288 this is 9V battery, with working voltage of 7V (used one).

[Kiriakos GR]

PART 2 

Major problem with young people and hobbyists (when they publish their electronic projects over the internet or when they mimic adults product reviewers on camera), this is that they do not have true test and measurement equipment, and even the required knowledge, so them to produce an opinion which qualifies to be taken under consideration by others.

How in earth no one ever noticed that performance of DSN-VC288 this is closer to riding a bicycle this having square wheels than round ones ? 

Any way, lets hope that my own tests them will deliver the message to all ages of consumers so them to act more wise from now and on as buyers.

Regarding DSN-VC288 PCB, I did notice that I-ADJ pot and near by voltage divider was not identical to all batches of PCB.
SMT resistor next to the pot was different in some product pictures, but such a manufacturing difference this also translates, that value of pot in Kilo Ohm, this will be different too.

In my case I had to experiment by another value of resistor so this voltage divider to work in my benefit.

I am unable to celebrate even if my conversion this it did worked, because even if I manage to force DSN-VC288 this to measure somewhat accurately at 1~4 Amperes range (which this is most essential to me), my victory this is DSN-VC288 this measuring only 1A less at 10A real current flow, when DSN-VC288 at default configuration this has almost 2.3A ERROR.

 
DSN-VC288 100V 10A, as voltmeter seems more reliable, but currently I did tested it up to 36.7V (which is the limit of my Kenwood PD35-10 Linear DC power supply).
 
 
My own lesson from this latest adventure which even forced me to drive up to nearest electronics parts store for buying additional resistors, this is that I am going to avoid buying or using any digital meter using negative side of wires for shunt measurement.
Also I am now aware that electronic design of DSN-VC288 this is a failure which it should be removed from the market.

 

[Kiriakos GR]

For DSN-VC288 PCB there is one Undocumented RESET function.

Supposedly this RESET function it is there so this to remove unwanted counts if there is a displayed value when actually, voltage and current input this is zero.

To activate RESET you just need to short pictured PCB pads, and to power-on the meter by having previously disconnect both shunt cables and voltage cable (measuring +).
At power-on with jumper in place, you will note both lines of LED to become momentarily shorter in digits, removal of jumper this should follow 2~3 seconds after power-on, then all digits appear again  (full display resolution Mode).

In my case this RESET functionality somewhat forced both meters them to restore correct linearity when them measuring current, and now both meters operates correctly.
Personally I am not convinced that RESET functionality this can also be the cure if Ampere ADJ pot this is out of range due wrong resistor over the PCB.

By mentioning all issues at eBay seller, he gave me 50% refund and therefore I feel as compensated for the troubles that I got to.
What forced me at discovering RESET function was the refund plan of specific seller, he advised me about me getting a hammer and smash the meters, send him a picture, and then I will get full refund.      

According my thinking and moral values, I feel like be a doctor, and I do take joy from bringing back to life of anything powered with electricity.
But from an consumer perspective, if you are unable to handle such manufacturing defects due lack of skill or tools, I will advice you to use the hammer. 
When you do so, the manufacturer will be also forced to refund the seller whom sold the goods to you.
And by him starting loosing money ....  he will be forced to increase QC inspection, and by doing so he will also minimize manufacturing process errors.

Because some people they do think abnormally, I will say to them: NO it does not make sense using RESET function at bright new meters, so them to recover in functionality level.

If my tip saved your day ... you are obligated to donate at ITTSB Blog. 

[xavier60]

There are multiple versions of "DSN-VC288" avaiable.
There are differences in PCB layout which don't affect performance.
There are differences in the micro-controller's firmware that can degrade performance.

All of the meters I have bought recently have a permanent negative offset in the current or voltage range or both, despite doing the zeroing procedure. Also look for the reading jumping from 0.00 to 0.02 or 0.03.
This results in the displayed reading not accurately tracking the actual input.
There is also a trend of increasing the refresh period.

Three meters I bought from Banggood all have the same problems.
The refresh period is a very slow 800mS although it is advertised as 300mS.
If I calibrate the voltage at 5V, the meter will read 20.5 when I input 20V. I did the test with the meters powered with a separate supply.  The current range is good except for some drift when the PCB is stressed, because of the LM358.
https://www.banggood.com/Mini-Digital-Voltmeter-Ammeter-DC-100V-10A-Panel-Amp-Volt-Voltage-Current-Meter-Tester-0_56-Blue-Red-Dual-LED-Display-p-1422461.html?rmmds=myorder&cur_warehouse=CN

Problem is no one notices, so the sellers get no feedback.

It's frustrating to watch old Youtube videos to see that the refresh used to be much faster,

[Kiriakos GR]

Problem is no one notices, so the sellers get no feedback.

It's frustrating to watch old YouTube videos to see that the refresh used to be much faster,

You and many others you do live by the false impression, that the makers of these products they are people which they do care of what they deliver.
The entire topic this delivers one message and this is: KEEP AWAY from these poorly made toys.

Or use them at insignificant applications. 

[xavier60]

These meters aren't really that badly built and look rather quaint.
All of the annoying problems are due to unnecessary and poorly written firmware changes.

To prevent the last digit from spontaneously flipping from "0" to "1", they give the range a negative offset in firmware which then results in poor tracking accuracy.

Two arrived from an Aliexpress seller today,


The refresh is 500mS instead of the advertised 300mS. 500mS is much better than 800mS and quite acceptable.
The voltage range has some tracking error.
If I calibrate at 5V, it will display 30.4 when 30V is input.
Although the current range jumps from 0mA to 20mA, the tracking accuracy is good.

Buying "DSN-VC288" meters is now like a lucky dip. You might get something that's acceptable or something with a combination of very slow refresh and bad tracking errors.

Edit: The refresh of these is 2000mS,
 https://www.banggood.com/DC-100V-10A-Mini-Digital-Voltmeter-Ammeter-Voltage-Current-Meter-Tester-With-Blue-Red-Dual-LED-Display-p-1428299.html?rmmds=myorder&ID=513344&cur_warehouse=CN

[Kiriakos GR]

I never had too many expectations from just three digits resolution. 

But neither I would dare to test the latest 5 1/2 digits (five digits) similar volt meters, by spending my own money in to such an experiment.

DER EE in Taiwan, has also digital panel meters, their quality are not questionable, and you may order directly by paying with PayPal.
 

[xavier60]

Yes, they have the same kind of meter,
https://de.deree.com.tw/de-3150-02-led-panel-meter.html
Even the cutout is the same size.
I can't find the refresh spec yet.

[Kiriakos GR]

Just email them .. 

[aidept]

Hi. First time here, salute you all!
I have a strange version of this product, with NO internal shunt and with a VERY BIG external shunt.
Wonder how low can this device measure the current? Can I measure, let's say, 4 mA?
Or the lowest value is 0.01 A (10 mA?)
Thank you all, fine people here.

[Kiriakos GR]

Hi. First time here, salute you all!
I have a strange version of this product, with NO internal shunt and with a VERY BIG external shunt.
Wonder how low can this device measure the current? Can I measure, let's say, 4 mA?
Or the lowest value is 0.01 A (10 mA?)
Thank you all, fine people here.

I would not trust even the 100mA measurement regarding the digital display capability.
Any one care for low current measurement he should get the one with the lower as Max Ampere range.
If there is one at 0~3A this would have better resolution than one at 0~10A. 
 
I have better luck with such gadgets with the ones of four digits resolution. 
https://www.ittsb.eu/forum/index.php?topic=1244.0

[xavier60]

A quick search indicates that these meters are used with a 75mV shunt. Meaning that 75mV drop across the shunt will give a full scale reading.
Google " Kelvin connection"