Multi channel Energy Meter - CT connection question

Other Hardware General Electronics
1

Hi,

I am designing a multichannel - multi-phase energy meter based on the BL0910 energy meter chip .
bl0910.pdf (2.1 MB)
I am using clamp CTs instead of the direct current measurement with a shunt resistor suggested in the datasheet at page 104.

I came accros two configurations for this :slight_smile:

image

and .

image

The first one appears to connect the zero potential "earth" at the center while the second one doesn't.

Can anyone explain what difference does this make for this application and which one is the best option?

Thanks!

2

Why don't you use the one shown in the data sheet
RL is the burden resistor.
image

3

Why don't you use the one shown in the data sheet
RL is the burden resistor.

In the Datasheet RL is a shunt resistor through which the WHOLE mains load current flows. For a number of reasons (avoid high currents on PCB, practical issues when having lots of channels, easier to install CT , etc) decided to use a clamp CT (Current Transformer) instead of a shunt resistor.

4

You should use the same circuit. RL is now the CT burden resistor.

5

You mean I should then calculate RL so that the voltage across it is the same as if I had a 1mOhm shunt resistor shown in the datasheet?

6

No, you should use the burden resistor value specified by the CT manufacturer

7

Hi, @Watcher
Welcome to the forum.

I don't think so, you need to research how CTs work.

Can you please post a link to specs/data of the CT?

Thanks... Tom.. :smiley: :+1: :coffee: :australia:

8

I don't think so, you need to research how CTs work.

Thanks but i know how CTs work.
I was referring to the BL0910 datasheet. There is no CT in the typical application schematic given there. It uses a shunt resistor instead.

9

That would depend on what you have decided to call GND in your application.

10

Digital GND and Analog GND are connected together

11

It's always best to follow the recommendations given in the data sheet. That way you know it will work

12

Yes, you are right.

13

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.