500A Shunt to 4-20mA Input

Hi all

Hoping somebody can help me here.

I have a system equipped with 500A / 50mV shunts and need to measure system current in the realms of 0.5A through to 150A DC.

I need to capture this data via a PLC 4-20mA input card.

Now I assume I should be looking for a 0-5V to 4-20mA signal conditioner.

Am I on the correct track here? Can anybody suggest appropriate signal conditioning hardware for this purpose?

As a separate query, I've been told by some to avoid using a hall effect sensor for measurement in favour of a shunt, as HA sensors are prone to drift. Considering I'm only dealing with DC measurement, what are your opinions?

Thanks!!

First Welcome to the PlcTalk community
I think you need a 0_50mV to 4_20mA signal converter
for the signal converter, here's a link from phoenixcontact, you can try also Weidmuller
https://www.phoenixcontact.com/onli...ndihisfwP1t7fq/#Z7_2G101H41MGE530Q8DDR7JM95G3

Here's a comparaison between shunt resistor and hall effect sensor:
http://whitewallenergy.com/lae/blog...against-shunt-resistor-in-monitoring-systems/

https://www.automationdirect.com/adc/Overview/Catalog/Process_Control_-a-_Measurement/Signal_Conditioners/Universal_Input

The above is a universal signal conditioner from Automation Direct.

Here are a couple of threads that may help:
http://www.plctalk.net/qanda/showthread.php?t=44047
http://www.plctalk.net/qanda/showthread.php?t=31221

Regards,

Bergermeister said:

Hi all

Hoping somebody can help me here.

I have a system equipped with 500A / 50mV shunts and need to measure system current in the realms of 0.5A through to 150A DC.

I need to capture this data via a PLC 4-20mA input card.

Now I assume I should be looking for a 0-5V to 4-20mA signal conditioner.

Am I on the correct track here? Can anybody suggest appropriate signal conditioning hardware for this purpose?

As a separate query, I've been told by some to avoid using a hall effect sensor for measurement in favour of a shunt, as HA sensors are prone to drift. Considering I'm only dealing with DC measurement, what are your opinions?

Thanks!!

Click to expand...

What you have described, a 500A:50mV shunt, will generate, on its sensing terminals, 50mV when 500A is flowing through it. Keep in mind that the 50mV signal is 'differential', and that, depending on the shunt and connection, will certainly not be near a 'ground' or 'common' potential. So, isolation and voltage isolation rating are key concepts to understand, and look for in a signal converter.
Also, if this is in a DC motor armature circuit, and if the DC motor is connected to a digital drive, you might not see what you expect (as you might of, had this been a Ward-Leonard, MG set driven armature). So, consider if you want an RMS signal, or not.

Since you're only using a top reading of 150A, you really only will see 15mV, so your converter can be set to 0.000 mV to 15.000 mV = 0AMPS to 150AMPS. = 4.0mADC to 20mADC on the output.

Wow guys,

Thanks so much for your responses and links, you've gone above and beyond my expectations and provided some fantastic references. Thanks for your input, I greatly appreciate it.

You blokes sure know hot to make a long time reader, first time poster feel welcome

jdbrandt said:

Keep in mind that the 50mV signal is 'differential', and that, depending on the shunt and connection, will certainly not be near a 'ground' or 'common' potential. So, isolation and voltage isolation rating are key concepts to understand, and look for in a signal converter.

Click to expand...

Thanks Jeff, are you able to explain this concept a little further, or point me in the right direction?

Incidentally, this application is pretty simple. I am simply using the shunt to measure power into and out of a battery bank. Charge parameters are pretty sensitive and having the capacity to measure low current accurately at the end of the charge cycle is very important. At the same time, I need to monitor bulk charge parameters which can hit 150A.