Load Cell on RS485 communication

Sudhir PIngulkar · Apr 9, 2012

I am working on a project which involves weighing and rejection. The Load Cell is connected to an Omron indicator which in turn is connected to the PLC on 485 protocol. I have been told that apart from the communication parameters i would also need a 'character string' to help the plc understand the form in which the data would be received. However Omron techs just don't know anything about such a character string. Also can someone help me with basics of RS instruction?? Help!!!

Banker · Apr 9, 2012

Hi

PLC type?
Indicator type?
How is the indicator connected to the PLC port ect?

Banker

nonuke · Apr 9, 2012

If the indicator has a 4-20mA Output, you can connect this
to an Analog Input in the PLC and forget the RS485 communication.

MrQ · Apr 10, 2012

Most Weighing instruments I have come across use modbus. Does yours?

Sudhir PIngulkar · Apr 12, 2012

Yes it does. We have so far been successful in using an RS instruction and fetching the data on RS485 protocol however we can interpret the data that is received. We were told that we need a character string from the indicator manufacturer but we are finding difficulties understanding the same.

Indicator Model : K3HB Omron
PLC : Mitsubishi Fx3U
RS 485 BD is used.

Help!!!

@nonuke : 4 - 20 has already been tried and is of no use since the accuracy is compromised to a great extent giving us a least count of 600 grams which is not acceptable. the indicator is giving a least count of 10 grams and hence it is imperative to have this shifted onto communication. Since Multiple indicators are used, we would require station numbers and hence RS485

david90 · Apr 12, 2012

Sudhir PIngulkar said:
Yes it does. We have so far been successful in using an RS instruction and fetching the data on RS485 protocol however we can interpret the data that is received. We were told that we need a character string from the indicator manufacturer but we are finding difficulties understanding the same.

Indicator Model : K3HB Omron
PLC : Mitsubishi Fx3U
RS 485 BD is used.

Help!!!

@nonuke : 4 - 20 has already been tried and is of no use since the accuracy is compromised to a great extent giving us a least count of 600 grams which is not acceptable. the indicator is giving a least count of 10 grams and hence it is imperative to have this shifted onto communication. Since Multiple indicators are used, we would require station numbers and hence RS485

Maybe you should investigate why the 4-20 signal is so off. I wonder why it's so inaccurate.

Sudhir PIngulkar · Apr 15, 2012

The 4 - 20ma module has a full scale value of 2000 and the load cell has a full scale capacity of 1000kgs. Hence it gives me a least count of 500 grams which is not acceptable. Anyway we were able to go through the manual and figure out the character string and have now successfully integrated the system on RS 485 protocol. The result is exact readings the way they are on the indicator and is working beautifully.

Reference : Omron K3HB Manual.
Section : 1-5, and 1-9 (Command and Response Frame)

Thank you all for your responses friends.
Bye for now!!!!

mgplplc · Friday at 12:20 AM

I am encountering issues with RS 485 protocol used with DELTA DVP 12SA2 PLC with extension module of DVP 04AD-S with Nuvoton chip connectivity please help me find a way to communicate

Load Cell on RS485 communication

Sudhir PIngulkar

Member

Banker

Member

nonuke

Member

MrQ

Member

Sudhir PIngulkar

Member

david90

Member

Sudhir PIngulkar

Member

mgplplc

Member

Similar Topics