High voltage/current sensing?

Thread Starter

mmasalme

Joined Nov 21, 2018
4
I have to design a schematic for an isolated voltage sensing circuit and isolated current sensing circuit.
Where should I start and is there anything in particular I need to know?
It should look something like this:





Mods Note:
The original links of circuit was wrong, the circuit above was copied from #3.
 

Reloadron

Joined Jan 15, 2015
5,126
There is no image attached which I can see? Also when you say:
an isolated voltage sensing circuit and isolated current sensing circuit.
What exactly with numbers are you trying to sense? For example I need isolated current and voltage sensing for 480 VAC 60 Hz 0 to 500 amps. You make no mention of AC or DC and the actual levels.

Ron
 

Thread Starter

mmasalme

Joined Nov 21, 2018
4
There is no image attached which I can see? Also when you say:

What exactly with numbers are you trying to sense? For example I need isolated current and voltage sensing for 480 VAC 60 Hz 0 to 500 amps. You make no mention of AC or DC and the actual levels.

Ron
Sorry for not elaborating, I am trying to design a circuit schematic that senses the voltage and current of an approximately 450V DC battery

Isolated V.jpg
 

dendad

Joined Feb 20, 2016
3,317
For current, have a look at..
https://www.allegromicro.com/en/Products/Current-Sensor-ICs.aspx
and https://www.allegromicro.com/en/Products/Current-Sensor-ICs/Fifty-To-Two-Hundred-Amp-Integrated-Conductor-Sensor-ICs.aspx

They are pretty easy to use.
For voltage, just a voltage divider would work ok. Use good quality resistors and a number in series so the voltage is spread over them, like in your circuit.
Do you need the voltage floating like you have it, or can the monitoring circuit share a common connection, usually 0V?
 

Thread Starter

mmasalme

Joined Nov 21, 2018
4
For current, have a look at..
https://www.allegromicro.com/en/Products/Current-Sensor-ICs.aspx
and https://www.allegromicro.com/en/Products/Current-Sensor-ICs/Fifty-To-Two-Hundred-Amp-Integrated-Conductor-Sensor-ICs.aspx

They are pretty easy to use.
For voltage, just a voltage divider would work ok. Use good quality resistors and a number in series so the voltage is spread over them, like in your circuit.
Do you need the voltage floating like you have it, or can the monitoring circuit share a common connection, usually 0V?
"Floating" as in isolated?
 

Thread Starter

mmasalme

Joined Nov 21, 2018
4
Your circuit does not have either the HV+ or HV- connected to the monitoring circuit 0V/gnd connection.
Is that so?
Yes one of the requirements is to keep HV+ and HV GND completely isolated from the LV+ (24V) and LV GND.
But then how do we power the LV side?
 

Reloadron

Joined Jan 15, 2015
5,126
If this is for a commercial application where accuracy is important as well as isolation I would likely choose an off the shelf turn key solution along these lines. You can choose outputs like 4 to 20 mA or 0 to 10 VDC proportional to the input. They are not quite inexpensive but when you want total isolation and an output which is precise and scaled to the input anything similar would be my choice. I would do the same for the DC current sensing. I have used the CR Magnetics line in the past and like them but there are likely a dozen manufacturers out there to choose from, maybe some very inexpensive stuff from China. They are 24 VDC powered, accurate and you can scale the proportional outputs.

Ron
 
Top