Voltage and frequency monitoring

Romanr9999 · Apr 15, 2009

Hi guys. I´m new here in this site although I´ve been working in automation for some time.
I received a project where I need to monitor either the frequency or the voltage value from a generator and make sure they stay within limits. Both frequency and voltage go up or down together according to the load attached to the generator, so I only need to monitor one of them.
This sounds really simple although I couldn´t find anyone selling a sensor I can use to sense voltage or frequency and input that value into the PLC.
I bet somebody else run into something like this.
Do I need a custom electronic module to convert from either frequency or voltage for the analog PLC input?
Thanks a lot.

tragically1969 · Apr 15, 2009

Romanr9999 said:
Hi guys. I´m new here in this site although I´ve been working in automation for some time.
I received a project where I need to monitor either the frequency or the voltage value from a generator and make sure they stay within limits. Both frequency and voltage go up or down together according to the load attached to the generator, so I only need to monitor one of them.
This sounds really simple although I couldn´t find anyone selling a sensor I can use to sense voltage or frequency and input that value into the PLC.
I bet somebody else run into something like this.
Do I need a custom electronic module to convert from either frequency or voltage for the analog PLC input?
Thanks a lot.

Personally i would use a power meter with communications such as Modbus etc. and read that back to the PLC:

http://global.powerlogic.com/products/meters_and_rtu/

montech · Apr 15, 2009

Just a thought but couldnt you monitir a tach pulse or an encoder on the motor?Im sure motor RPM would relate to both qtys you are trying to monitor.

Gerry_001 · Apr 15, 2009

Hello,
you can use a powermeter from Merlin Gerin Type PM500 (old model) or the model PM700 (newest is yet PM800) in combination with module 1AO.
This gives a analogue output 4..20 mA that you can read in the PLC. Within the PM700 you can set the range to this channel 0.400VAC or 0..50 Hz of KVA or KWh or ... (whatever you want). Then in the PLC you can scale it also and make some alarms of it.

Greetz (sorry for my englisch, its not so best)

kb9ttx · Apr 15, 2009

You might consider a Frequency Input Signal Conditioner such as the Dataforth DSCA45 frequency input module which provides a single channel of frequency input which is converted to a standard analog voltage or current output.

BobB · Apr 16, 2009

I normally use a Crompton blind digital power monitor and pull the info out via Modbus RTU.
Alternatively put an extra mag pick up on the fly wheel and use a high speed counter to monitor speed. Just be carefull though as mag pick ups work at fairly low voltage levels. Woodward have them for sale.

tomar_vikas · Apr 16, 2009

hi
if u are using an AB PLC you can go for AB make power monitor and get data by messaging or u can take any energy meter which supports modbus communication

seppoalanen · Apr 17, 2009

http://www.vegoy.fi/vamprussian/russian/support/documentation/VAMP210-ProfiBus3-50.pdf

Romanr9999 · Apr 20, 2009

Thanks a lot

I found locally a power meter with a 4-20mA as you suggested. That´s pretty easy.
Thanks a lot to all!

Voltage and frequency monitoring

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