4 to 20 mA output

theripley · Apr 9, 2010

Hi

What would be a possible error on installation or programming if I am reading 4-32mA at a 4-20mA module?

I am using an FX2N-4DA mosule connected to an FX2N base unit to control a VFD via touchpanel. If I set 30 Hz on the touchpanel, I should be reading around 8 mA on a meter. Instead I am reading 32mA. Setting 30-60 hZ gives me analog reading of 32mA.

I have read the manual & it says that if I chose current output mode of 4-20 mA, the offset data will automatically be 4000 & gain data will be 20000.

Lare · Apr 9, 2010

Problem can be galvanic isolation, your PLC ground is maybe on different potential than VFD ground.

What your mA-meter shows, if you disconnect wires and measure mA directly from terminal blocks on PLC cabin.
If reading is now 8mA and you connect wires and reading goes to 32mA, you will need galvanic isolator between PLC and VFD.

theripley · Apr 9, 2010

Lare said:
Problem can be galvanic isolation, your PLC ground is maybe on different potential than VFD ground.

What your mA-meter shows, if you disconnect wires and measure mA directly from terminal blocks on PLC cabin.
If reading is now 8mA and you connect wires and reading goes to 32mA, you will need galvanic isolator between PLC and VFD.

Hi Lare,

I did disconnect all terminations on my DA module but I still get the same reading.

I also included in my program the program sample on the manual regarding changing I/O characteristic but nothing has changed.

Could be a that my DA module is damage?

naag_slet · Apr 9, 2010

Then its not a problem with galvanic isolation.

where is your attachment?

can u please send me the i-o configuration screen shot atleast?if possible try to reset the module once...

theripley · Apr 9, 2010

naag_slet said:
Then its not a problem with galvanic isolation.

where is your attachment?

can u please send me the i-o configuration screen shot atleast?if possible try to reset the module once...

Hi Naag_slet,

Kindly see my attachment as written on the manual. I am sorry I could not give a attach a screen preview of my program because the program is on my laptop. I could not connect my laptop directly to the office's LAN, it is strictly prohibited specially if no IT is around.

Although I did revised what is written on that sample program like I made k1 to k0 (as my DA module is the 1st module after my base unit), x0 to m8000, timers, etc.

I hope you could help me out on this.

theripley · Apr 9, 2010

naag_slet said:
if possible try to reset the module once...

How would I be able to reset the module? Turning the breaker off?

naag_slet · Apr 9, 2010

Please find the attached doc and seach by typing reset,

Go ahead to reset the module to factory setting by program...
and then set your offset and gain..
gud luck...
Naag.

Jeff23spl · Apr 9, 2010

configured or wired as a voltage output 0-10 so as soon as the output turn a little bit on, it give full mA output until the usual 32mA protection....

look at wiring and configuration of your output

nonuke · Apr 9, 2010

At 30Hz in a scale from 0 to 60Hz, you should be reading 12mA no 8 mA.

theripley · Apr 9, 2010

Jeff23spl said:
configured or wired as a voltage output 0-10 so as soon as the output turn a little bit on, it give full mA output until the usual 32mA protection....

look at wiring and configuration of your output

Hi Jeff23spl,

Im sorry but I can't seem to get what you mean here. Are you trying to say that I will alter my wiring from 4-20mA to 0-10 Vdc? Am I getting it right?

What would this do?

theripley · Apr 9, 2010

nonuke said:
At 30Hz in a scale from 0 to 60Hz, you should be reading 12mA no 8 mA.

Hi nonuke,

Still, regardless if its 12 or 8 mA (Im sorry if my calculations failed), 32mA is quite so high in a system that is supposed to output 20 mA as its peak.

theripley · Apr 9, 2010

Lost in translation

Also, I am confused with what is written on the manual (please refer to FX2N(1) & FX2N(2) on the attachment).

Quote "Switching the output mode resets the I/O characteristics to the factory-set characteristics".

What switching is it referring to? Am I not supposed to switch it?

Gil47 · Apr 11, 2010

Try using the values 2000 and 400 this is ten times less than you have been using and see if the results agree better as my reading of your number 2 PDF says that it uses 11 bits which to my reading is a max of 2048 = 20 mA

4 to 20 mA output

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