I have come to this thread late and admit that I have not read it all--so I could be just wasting your time. These kind of meters require a separate battery supply, not connected to the circuit you are measuring. As you say, there is an internal connection but you can't have any other connection. The meter can't get power from the circuit it measures.

There are some that cannot, but there are some that can. This one is the latter type. See my photograph above.

 

OK....I will a use 9v battery for the display and will report back

 

Now I separated the two circuits. The Display ( Thin Red and Thin Black) are connected to the display using 9v battery
Display OK Both Current and Voltage Display zeros.
The main circuit: Yellow to POSITIVE PS
The Thick Red and Thick Black to the NEGATIVE of PS.
Voltage OK ( 4.75 V) BUT NO CURRENT My meter reading is .6 AMP ( 6.6 ohm 50 watt Load)
Pls ignore the inaccuracy of my meter.

 

Try this:

Run the yellow wire to the + power supply and to one end of the load.
Run the black wire to the - power supply.
Run the red wire to the other end of the load.

 

Try this:

Run the yellow wire to the + power supply and to one end of the load.
Run the RED wire to the - power supply.
Run the red wire to the other end of the load.

As before The LCD is powered separately
Yellow to + PS
RED THICK to the -ve PS.
The Black Thick to the LOAD NO CURRENT reading.
I connected the BLACK THICK WIRE to Chassis I got a reading. This time "HALF" what I get before It display 18.4 ( my meter 0.54 AMp) !!!!!!!!!!
This is 4.92 V, 6.6 Ohm Load
It is funny, now I have to multiply by THREE Divide by 100 to match the meter reading.
Trust me I have a large mug of Coffee next to me...No empty beer bottles in sight !!!!!

 

I don't know you misquoted what I said, but in the second line you write that I said "Run the RED wire to the - power supply." but I actually wrote "Run the black wire to the - power supply." Try again.

 

I don't know you misquoted what I said, but in the second line you write that I said "Run the RED wire to the - power supply." but I actually wrote "Run the black wire to the - power supply." Try again.

I am really sorry for this misunderstanding.

Yellow to +ve PS Then to Point A of the load
Thick Black to -ve PS
Thick RED to Point Z of the Load

And YES I got a reading......BUT the value is meaningless; between 343.0 and 335.0 CONSTANTLY moving through the range
My meter is giving reading between 0.55 Amp and 0.54 Amp and CONSTANTLY moving through the range but slower .

My conclusion:
You obviously know what is going on.
The MCU (STM8S003) is not interpreting the voltage difference over the shunt properly.

Since I have another one, I will just replace the unit keeping everything as is and report back.

My apology again for misreading you CLEAR instructions.

P.S. The Voltage reading is 4.93 V( Steady) and the load is 6.6 Ohm.

 

Same behaviour !!!!!!
The display current range is a bit lower 322.0 to 318.0 The voltage is Steady at 4.92 V.

 

I have drawn out a diagram of the inside of the meter. Once you see it the connections becomes clear.

 

I have drawn out a diagram of the inside of the meter. Once you see it the connections becomes clear.
View attachment 150766

It is definitely clear. Thank you for taking the time to explain your wiring.
From "white haired to another" What Do I do with this weared reading after all I need to know what current I am using. Shall I just buy new ones or there is a hope of making sense of the weared values. There is this mysterious button that MUST have a function !!!! for example calibration which the topic in hand now.

So, I experimented:

Pressing while the system is on had no effects at all.
So, I switched off then ON while pressing it. I got the CURRENT displaying C - - C then turned to - - 0 0 When I press it repeatedly I got 1, 2, 3 .....
i.e. - - 0 1, - - 0 2 ........

I switched off after reaching - - 1 0 , got back the same reading as before 4.87 V 29?.? as before but LOWER

 

You should never press a button if you don't know what it is for. Mark that meter so you won't get it mixed up with the other one and put it away for now. Later I'll see what I can find out about how to use it, but not now.

Get out the meter you have not pushed the button on. It is possible you have damaged this meter by connecting it incorrectly, but they are pretty tough, so it is probably ok Tell me about your power supply--is is a commercial one? homemade? a kit? If you made it, post a schematic.

What is your load--a resistor (what wattage is it), a light bulb, a motor? You say it is 6.6 ohms--how do you know?

Now, let's hook it up. Connect your battery to the thin wires to power the meter on. NO OTHER WIRE is connected to this battery. Connect the yellow wire to the load and the + power supply. Connect the black wire to the - power supply. I think you have said many times that this much works as expected and that you get a voltage reading of almost 5 volts (I assume your power supply is set to deliver 5 volts. The ammeter portion should read 0 since the load is not connected on the other end. Is this correct? If not, tell me what it reads.

Now connect the Thick Red wire to the other end of the load. This is where you say get weird readings. Tell me what you see. Do the numbers change at random? Do they go up for a while and then down? You should be getting a little over .75 amps (or 750 mA if it is calibrated in mA.)
If the load is a motor, does its turn? Is it steady or fast then slow? If it is a light bulb or LED fixture does it get brighter and then dimmer? If it is a resistor does it get hot?

 

You should never press a button if you don't know what it is for. Mark that meter so you won't get it mixed up with the other one and put it away for now. Later I'll see what I can find out about how to use it, but not now.

Get out the meter you have not pushed the button on. It is possible you have damaged this meter by connecting it incorrectly, but they are pretty tough, so it is probably ok Tell me about your power supply--is is a commercial one? homemade? a kit? If you made it, post a schematic.

What is your load--a resistor (what wattage is it), a light bulb, a motor? You say it is 6.6 ohms--how do you know?

Now, let's hook it up. Connect your battery to the thin wires to power the meter on. NO OTHER WIRE is connected to this battery. Connect the yellow wire to the load and the + power supply. Connect the black wire to the - power supply. I think you have said many times that this much works as expected and that you get a voltage reading of almost 5 volts (I assume your power supply is set to deliver 5 volts. The ammeter portion should read 0 since the load is not connected on the other end. Is this correct? If not, tell me what it reads.

Now connect the Thick Red wire to the other end of the load. This is where you say get weird readings. Tell me what you see. Do the numbers change at random? Do they go up for a while and then down? You should be getting a little over .75 amps (or 750 mA if it is calibrated in mA.)
If the load is a motor, does its turn? Is it steady or fast then slow? If it is a light bulb or LED fixture does it get brighter and then dimmer? If it is a resistor does it get hot?

I put my sleeves up toooo
Here we go:
1. The power supply is a very expensive PC SWITCHED POWER SUPPLY, I had no use for ( Made by Antec, True 480 Watt )
2. The Load is 5@1 10 Watt Ohm, connected in series to a total of theatrical 5 Ohm, but when heated they total 6.6 Ohm ( 50 watt)
I connected them in a way that I can select from 1 to 5 ohm load to see if the current reading did change. And The weird values actually changed.
3. The power supply provides 3 voltages 3.3v, 5v, and 12 V. I am using the 5 V source.
4. All the three voltage sources are connected to a large Bread board That Has four Input plugs for the 3 voltages and ground FROM the PS.
5. All the voltages reported OK.
6. The PS has auto short circuit protection ( life saver when you are exprementing !!!)
7. The unit is powered by 9 V battery and V, and C report 0 on their own.
8. Very interesting remark. When I switch off the power supply The display goes off AUTOMATICALLY
9. When I switch it on the display show the correct voltage and zero current ( NO LOAD)

NOW here is your instruction:
A.. Yellow to the + PS
B- Thick RED to the -ve of PS
C-From the +ve of PS to the meter (in series ) to the Load Terminal ( the "5" Ohm Load mentioned above)
D- The Black Thick wire to the OTHER side of the load
E- The meter reading is 0.53 Amp and steady. THE CURRENT DISPLAY IS ZEROS. The voltage Display is 4.86 V

I have another meter to report voltage readings:
1. Accross PS 5V No load
2. LOAD is 7 ohm ( it was hot a little) Not switched on yet.
3. PS ON and LOAD ON. Meter .56 AMP DISPLAY CURRENT ZEROS
4. Voltage Displayed 4.94 V , metered 3V accross the load.
5.Connected the Black Thick wire to the other end of the load. NO DISPLAYED CURRENT and the meter is 0.51 Amp

 

You are not reading me--the RED wire does NOT go to the power supply--it goes to the low end of the load and it is the ONLY wire which attaches to that end of the load.

 

You are not reading me--the RED wire does NOT go to the power supply--it goes to the low end of the load and it is the ONLY wire which attaches to that end of the load.

I connected the RED wire to the end of the load Now I am reading 84.0 to 86.4 ?? and Voltage 4.93 Steady The meter is 0.56-0.54 Amp

I was just testing you.... You passed full mark

Now how we interpret 85 to .be a 0.55 Amp

 

correction.....NOW the ONLY wire connected to the load is the red wire,

The reading is 460 and the meter is .46 Amp.............. WE ARE ALMOST there

 

Actually WE ARE THERE.....The Display is 470 mA right to to dot.

 

Good. Now, using the 5 volt power supply and only the 5 ohm resistor you should get very near 1 amp. 5 ohm resistors are often + or - 10%. If you get within that for your reading, consider yourself successful.

Now, there is very little on the internet about that calibration button. On one meter you are to turn the meter on with the battery, short two wires and press the button. But it never says which two wires. My first try would be the yellow and black. If that doesn't work try red and black. Then red and yellow. Or, your meter could be totally different.

 

Now what we need is to remove the novice from your name, and attached it to mine.
And we call it a day.

 

I would like to thank whitehaired novice for his guidance AND patience to achieve a solution to my problem.
His support and vision saved me the trouble of of reaching wrong conclusions.