[SOLVED] Need some help regarding MCP 3901 Energy Measurment IC

[ADGAN]

Hi! I need to develop a energy meter for my HND diploma project. I'm hoping to use MCP3901 to measure the energy consumption of the load. I went through the datasheet & the reference design. The reference design has been designed using PIC18F65J90. ( **broken link removed** )

My first problem is whether it is possible to use a different microcontroller than the PIC18F65J90, if so I'm hoping to use a one from PIC18F family like PIC18F45J10 which is able to connect to a breadboard and has a built-in EEPROM. (I'm more familiar with PIC16F887) Does it really necessary to use an external EEPROM. If I use a different microcontroller will it affect the calibration process?

Another problem is that why does this meter needs to be calibrated ?

Finally, can somebody explain me the use and the specification of the line shunt (current & voltage) used in the reference design & where can I purchase it online and also what is name of the black colour component connected to the line shunt which is in the bottom of the meter to connect the wires. :-D

Pls I really need an answer

Thanx in advance

 

[Hisham.D]

Question 1 : Yes it is possible to use any mcu as long as it has an SPI communication.
Question 2: The eeprom cam be whatever you want it is used in this application to store the measure energy.
Question 3: Calibration precision is the same regardless of what mcu you use
Question 4: All meters need calibrations, since the measurement is affected by the components and tolerances you use, moreover with the value of the shunt resistor or any other current sensor you use and so on...
Question 5: In order to measure the current, the IC needs to transform it to voltage. Thus the current is passed thru a shunt resistor and using the voltage across the resistor and Ohm's law one can get the current. (http://www.measurementest.com/2010/08/how-to-measure-current-using-shunt.html).
If you don't know what you are doing, try using a current transformer instead
Many places where you can purchase a shunt resistor, digikey, mouser, aliexpress ...
Question 6:Not sure if you mean the screw terminal

 

[ADGAN]

Thank you very much for the reply sir.

Can you explain the answer for the second question. Sorry can't understand your answer.

If the maximum current is 60A since the maximum voltage allowed on the pin is 1v then the shunt resistance should be about 16mili OHMs is it?

If I use a current transformer instead of a shunt then I would have to connect it to the IC just like connecting a shunt ? Then what are the values of the transformer would be?

Yes sir what I meant was the screw terminal

 

[Hisham.D]

The eeprom is used to store the calibration factors, energy consumption and some other variables (in case of power loss, the values will be saved so that on next boot they will be reloaded) .. It doesn't matter where the eeprom is (internal or external).. The only thing that matters is the size of it..
If you know what you are doing then stay with the shunt resistor . Your calculations seems correct for the value of the shunt resistor.
On page 22 of https://ww1.microchip.com/downloads/en/DeviceDoc/51915A.pdf you can see U1 and U10 these are the current transformers and how to interface them. You might need a burden resistor for your current transformer if its output is current (i.e the rating is something like 60:5), then use the same method to calculate the burden resistor as the one used for the shunt resistor but now the current is 5 rather than 60 (using a 60:5 transformer).

 

[ADGAN]

Thank you sir understood :lol: