Modbus data convert to analog signal

[JERA]

I need a good idea to solve a small task.

My customer bought a measuring device where the measurement is collected by a controller from a wireless sensor and there should have been an analog signal out for the measurement. But it turns out that the analog signal is only present if the sensor is connected directly to the controller.

I can get the data via Modbus, but the PLC system does not have the option of connecting bus systems.

So I am looking for a device that can receive measuring data from the bus and convert it to analog signal 4-20 mA.

 

[KalleOlsen]

I can get the data via Modbus, but the PLC system does not have the option of connecting bus systems.

What type of PLC system is this?

And is it serial Modbus (RTU/ASCII) or TCP/UDP-IP?

Kalle

 

[danw]

The device is undoubtedly a Modbus slave/server, which means you need a Modbus master to read its data.

Two approaches come to mind -

1) Red Lion's Data Station Plus with a Modbus-to-AO module, or Red Lion's Process Automation Controller which is CPU with modular I/O. Neither is an inexpensive option.

2) Use a low end PLC like an Automation Direct with the CPU Modbus master option and an AO module.

Maybe replacing the PLC with one with Modbus master capabilities makes more sense.

 

[JERA]

Hi

Thanks for the reply.

It is Modbus serial RS485 in ASCII mode.

The old PLC systems is Siemens S5-95 + S5-115 systems, and it is 5 systems total. So the replacement of PLC systems is a larger task and is my client is not currently interested in this.

I'm also for a solution with a micro PLC with Modbus interface and one analog output. It is a simple solution where I can check the data and make a controlled conversion.

So thanks for the ideas

 

[kittydog42]

You might be able to do this with a simple PID controller that has Modbus. Simplest and cheapest option.

 

[RET]

If you can configure the wireless controller to be a Modbus Master device, then you can use something like this...

http://www.dghcorp.com/d3000m/

 

[a062549]

If you can configure the wireless controller to be a Modbus Master device, then you can use something like this...

http://www.dghcorp.com/d3000m/

I've used the ICS version of the Modbus-analog with good success. Also used the Phoenix and IDEC "reasonable" plc's for this purpose too.
If your client it considering going to a newer PLC system, then this maybe a good point to start selling your services!