Considerations about Low Current bench-top digital power meter up to 600V

[Kiriakos GR]

Low Current bench-top digital power meter up to 600V, this is required instrument for low current measurement capability.

We thinking to shrink down pricing costs, we will aim for the market of Low Current bench-top digital power meter.
Such product's they are using precision sense current resistor.
They are available exclusively in China.
They have current range this starting from 0.3mA up to 2A or 3A.
They have four digits resolution at Max for Voltage, mA & A, W, PF and Hz.
They have four LED windows, and a mode switch for PF or Hz.

List of considerations:
These are actually two. 
First one this is of how we can protect current sense resistor from the extreme inrush currents ( start up current of pulsing power supply).
The two or three manufacturer of such products, they deliver only over-current safe limit 1.2 times over the max.
For the two Ampere meter, this is 2.4A
For the three Ampere meter, this is 3.6A

What if we need to measure low current of a larger power supply at 700W with inrush current of 20A?
Currently the only solution that I can think, this is one external power switch, this creating a sort between the two current shunt terminals.
As soon the PSU has been powered,  this switch it can be turned off = free current flow (ACA) due the measuring current circuit.

Second consideration:
In case that there is a communication port at the back of the instrument?
In order this to be connected safely with a personal computer, it is required a communication box, so this to offer electrical isolation.
Electrical isolation required not only for data line safety.
Any digital power meter connected to mains, this is in risk so to engage at over-voltage accident.
In the worst scenario, the over-voltage it might travel due the data communication port and damage the connected PC at USB or RS232 port.

Currently I am a bit confused, of what might be the best isolated communication converter box?
The advertising speaks about two product's.
a) electronic isolation due active and passive components.
b) opto-isolated communication, but even at this solution the DC to DC isolation converter, this is not any different, from the one at the electronic isolation product.

Quick conclusion, at low price instruments, you might need to add externally a few missing features, so them to become a complete solution.

[Kiriakos GR]

I have find a significant information this week, about electronic isolation due active and passive components.
Waveshare brand, this using electronic isolation components these based on fresh developed technology.

https://www.ittsb.eu/forum/index.php?topic=1970.0