Voltage Measurement in Noisy Environment

[roydm]

Hi, I am working on a large storage battery where I need to measure the voltage of individual batteries.
Associated with the storage is a large bi-directional inverter which is extremely noisy (RFI)
I need to measure individual battery Voltages around 100 Volts. Past experience tells me that electrical noise will be a big issue so I would really like to couple the transducers to the PLC via fiber optics.
So far I have only found one supplier whose transducers require a separate fiber to Voltage output module these extra steps seem to me to be over-complication.
I imagine some sort of network like the RS-485 Master Slave arrangement often seen in switchgear only fiber of course.

Has anyone seen anything like that?

Thanks
Roy

 

[itsmoked]

Hi Roy,
Have you looked at Linear's battery monitoring chip? It's specifically for individual battery monitoring in series strings. They seem to have thought of everything.

LTC6802-1
or
LTC6803-3

They may have more too.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[roydm]

Keith,
I just looked at the two devices you mentioned unfortunately the Voltage rating is too low, we need to measure batteries in series not individual cells, the LTC68 series has a maximum Voltage rating of 60 Volts

I made another post under Electrical / Electronic Engineering other topics
Thanks for responding
Regards
Roy

 

[IRstuff]

What's actually getting noisy? Is it the measurement itself, or the PLC getting upset by all the noise?

TTFN
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[Skogsgurra]

roydm
There are wonderful lowcost passive devices which can be used as voltage dividers. Wouldn't they work?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[itsmoked]

Hi Roy,

This just feels wrong to me. Seems like way to much hassle.

I think if I were faced with the same issue I'd:

1) Try to reduce the EMI being spewed into the battery stack. Include perhaps some capacitors to shunt the noise from the inverter. Possibly a choke too?

2) Find a digital meter that has 485 output that allows you to poll it.

3) Get a handful of 485 isolated adapters.

4) Network your meters thru the isolated 485 adapters.

5) Hook your PLC as a MASTER to the now isolated 485 network.


Keith Cress
kcress -

http://www.flaminsystems.com

 

[roydm]

Gentlemen.
Thankyou for all the good ideas.

IRstuff;
We don't have it built yet, Im just trying to avoid the problem we experienced last time
The vendor described his inverter as "A radio station in a box"

Skogsgura,
I'm not sure how I could use those, everything we purchase will have to be approved.

Itsmoked,
This is pretty much the conclusion I have come to
1) I will ask the engineer to get tough on the vendor
2) I have located some likely looking transducers
3) Good idea
4) I was hoping I could isolate the transducers from the PLC via fiber optics rather than running copper from a noisy environment to the PLC, I haven't given up on that yet.
5) Yes, that's what I was hoping to do, avoid having to convert the measurement twice.