Problems analogue signal 5

[flinana]

Hi,
I have the following problem. I am suppose to receive a 4-20 mA signal from a system called TELEFLO DIVA supplied by Air Liquide.
Problem arises that when i connect the two wires to our plc input card (configured as active) we read nothing. However wheni connect a 4-20 mA generator (as passive) and generate to the card it read ok. I belive the signal is given in parallel and not in series, could this be?

I attach the diagram that was given to me.

 

[xnuke]

I got next to nothing from your diagram. It isn't specific enough.

From your text description, it sounds like the Teleflo Diva is a four-wire device and the PLC is expecting a signal from a two wire device. That can be corrected with a signal isolator.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[flinana]

thanks, i did the drawing in paint in 2 minutes, but believe me the original isnt much different. Problem is that according to the diagram it only needs two wires and if it is 4 it should have been drawn as such. I am attaching a photo as we speak.

I think the second picture tries to say its 4 wire, however when we generate mA with a Fluke to their terminals it seems to work, so i dont kno what difference ther can be between the Fluke and this Teleflo DIVA of which a find no info on the web btw.

 

[djs]

Ok the second diagram clears it up. The Teleflo is a two wire device. This means that it controls the current, but does not supply it. You need to add a power supply in series with the current loop in order for it to function. The change is simple, look at the top diagram of your second image. Connect the loop like that and it should work. The positive side of you analog input should connect to the 24 VDC terminal of the Teleflo. The negative side of the analog input should connect to the analog output of the Teleflo. Hope this helps.

 

[flinana]

thanks for your help. However If i set my Analogue output in my PLC to Active it the supplies the 24Vdc in the current loop, why would I need an external power source?

 

[flinana]

According to the top image thats the way to connect if i want the signal as Active (i.e power from Teleflo) and the bottom pic as passive (i.e. power from card). What you are saying is to make my card active and connect it as the top diagram? but then I would have two 24 Vdc connected together right?

 

[amptramp]

Who makes the analog card and what is the part number?

 

[flinana]

Its called METSO from Finland, I will have to look it up. What exactly would you like to see from the specs? We have many passive instruments connected and so far no problems, even signals from frequency converters which are active are also ok.

 

[amptramp]

I want to read the instruction manual so I can create a drawing showing how to wire your analog signal. The previous posts have described how to wire up the signal, but you are still having problems so I thought I would make a drawing.

 

[flinana]

Ok, find the requested manual attached. The card we are using is AI8C D201134.
Correct me if I am wrong but this is how I understand this.
If I want the 24 Vdc supply to come from the TELEFLO I configure my card as Passive and connect to terminals 14 and 12 on the Teleflo, On the contrary if I want the 24 Vdc supply to come from my card I configure my card as Active and connect to terminals 13 and 12 on the Teleflo.

 

[amptramp]

flinana:

Try the configuration on the attached drawing. Set the jumper on the analog card from FP to COM (I think Passive is how you refer to this setting). If the loop still does not work, please let me know.

 

[flinana]

Amptramp, I have done as you say however the problem is that setting both my card and their system to passive there is o Vdc in the loop. If I set my card to passive and connect to their terminals 12 and 13 I am connecting to potential free contacts. If I set my card to passive according to the diagrama I should connect to terminals 14 and 12 but it still no go!

thanks for your help

 

[amptramp]

flinana:

Please try the new configuration in the attached drawing.

 

[flinana]

I just uninstalled acad, can you attach it as pdf, thanks

 

[amptramp]

flinana:

I noticed I posted the ACAD drawing file (.dwg) instead of the .pdf file. Please find the .pdf file attached below.

I chose the new wiring configuration based on the observation the Teleflora analog ouput is a "sinking" output. However, even if the new configuration works, I would not be comfortable with this wiring arrangement. The Metso analog input card is a single-ended card. On a single-ended input card, all channels share a common connection. The wiring diagram I posted basically sets the analog output from the Teleflora on "top" of the channel's 249 ohm resistor. I do not know what kind of interaction this configuration would have with other channels on the input card.

Do you have a circuit diagram for the Teleflora analog output (similar to the diagram for the analog input found in the instruction manual you posted)? This information would be helpful.

Finally, the easiest way to get the loop working, as xnuke suggested, is to utilize a signal isolator.

 

[flinana]

Cheers amptamp, I have tried this new configuration too and nothing, just changing the polarity. I will try using the isolator although I believe my colleagues have tried too, I will try it again anyway.

 

[flinana]

and no unfortunately I have no more info from Teleflo.

 

[amptramp]

Cheers flinana:

I would really like to find a solution to your problem. Is there any way to obtain a circuit diagram for the Teleflora analog output?

 

[amptramp]

flinana:

Ok. If you get the loop working, please post the solution.

Also, sorry for the misspelling of Teleflo.

 

[flinana]

The strangest thing is that when i use a multimeter and connect the lead to the +24Vdc from the Teleflo and the other lead to the GND i do read the correct mA!!