Can we connected HART Transmitters to conventional 4-20 analog input card of PLC

[gspatil]

I have some HART transmitters flowmeters & Temprature transmitters...can I connecet it to 1756 - IF 16 analog input card of Controllogics PLC....?

I am confused because I have connected two Txs among which 1 is giving some reading....but not showing mA current when measured....both are temperature transmeters.

can we directly measure its 4-20 current signal using multimeter ?

 

[ndzied1]

I have some HART transmitters flowmeters & Temprature transmitters...can I connecet it to 1756 - IF 16 analog input card of Controllogics PLC....?

I am confused because I have connected two Txs among which 1 is giving some reading....but not showing mA current when measured....both are temperature transmeters.

can we directly measure its 4-20 current signal using multimeter ?

HART superimposes a frequency signal on top of the 4-20ma signal. According to the spec, this signal is 1200Hz for a digital 1 and 2200Hz for a 0.

If you set up the analog input with a filter significantly lower than 1200Hz I think you will be fine. 120Hz or 60Hz should be fine. I think your meter will likely have its own internal filtering and be fine as well. In any case you won't damage the analog input or meter so I'd hook them up and try...

 

[labeledas]

I have some HART transmitters flowmeters & Temprature transmitters...can I connecet it to 1756 - IF 16 analog input card of Controllogics PLC....?

Yes I have never had issues running HART enabled field devices to non HART I/O cards.




I am confused because I have connected two Txs among which 1 is giving some reading....but not showing mA current when measured....both are temperature transmeters.

make sure they are wired correctly and channels on your IF16 are enabled. Also what do you mean by not showing mA current, are you talking about the raw data going to your I/O card in RSLogix, if so you can change the scaling on your input channels to read out various engineering units including mA



can we directly measure its 4-20 current signal using multimeter ?

Yes depending on if its a active or passive transmitter the setup will be different.
passive you will need an external power supply most like 24vDC but verifying against manufacturer schematics. I have never done it with a multimeter only a loop calibrator but I believe those just act like an ammeter when in measurement mode. also you multimeter will need the ability to read dc mA

 

[DwSoFt]

Are they loop powered? I know many flow meters are not. And then their current output can be active (supplying power) or passive (needs loop power provided) so.tjat could.be a problem. Also is the common of the card connected to the same.24vdc negative? If not.no current will flow

 

[CRMCC]

I have used Hart flow meters connected to regular mA input cards. The only time it was an issue was when some sausage fingered tech had set an address for the unit, this then enabled the hart protocol and no mA signal was seen on the input card of the PLC. Changed the address of the unit back to zero and all was good again. The flow meters were Endress & Hauser but the Hart protocol is multi drop which is when you would use the addressing option, but then a Hart input card is required.

 

[danw]

some sausage fingered tech had set an address for the unit, this then enabled the hart protocol and no mA signal was seen on the input card of the PLC. Changed the address of the unit back to zero and all was good again. The flow meters were Endress & Hauser but the Hart protocol is multi drop which is when you would use the addressing option, but then a Hart input card is required.

When a transmitter has a HART address of zero, it knows that it is in a point-to-point connection.

When a transmitter has a HART address other than zero, it thinks it is on a multidrop network.

The network for all the HART transmitters on a multidrop HART network runs with fixed 4mA (that provides a source of loop power and a highway for the HART data), so the HART multidrop wasn't 'no mA signal', it was a fixed 4mA signal for the multidrop bus.

I'm not sure whether a HART enabled AI card could be used for multidrop - the multidrops I've seen use a separate HART master in a HART mulitplexor, which acts as a gateway. It collects data on the HART side from the HART transmitters, then provides that data, multiple variables from multiple transmitters, as data in Modbus registers.

Dan

 

[labeledas]

All of the AB HART cards I have ever used have been point to point not multidrop.

 

[CRMCC]

Thanks Dan, yes it was indeed 4mA, I was just trying to indicate to the op that they need to be addressed as zero to use on a standard AI input card.

 

[gspatil]

How should I get 3 parameters of single HART transmitter in my Rslogics 5000

Thanks all of you for valuable suggestions.....I am getting data of HART Temperature transmitters (loop powered) on normal IF16 analog card.

But now I have a question the HART Flow or Pressure transmitters have multiple parameters like pressure, flow,temperature in it so how could I collect these all data of single HART transmitter in my RSlogics 5000 s/w using ladder....?

 

[danw]

This screen shot from
ControlLogix HART Analog I/O Modules, Publication 1756-UM533B-EN-P - September 2010

shows that the HART variables are somewhere in the controller:

This screen shot is an example of using pass through message to get HART variables:

That manual version is 214 pages. It's probably worth the read.

 

[gspatil]

Thank you very much sir...I cleared the point...Started working.