@ilr: "Hi
Firstly I am new to control and have more of an IT background so if my 
questions seem fundamental or are on the wrong track please excuse me.
I am involved with the development of a new sensor that will be used in 
industrial environments. We are at the stage where we are deciding how to 
communicate with this device that will ulimately be used for control 
purposes.
I have a few questions that I would answers to or some direction on the 
types of things we should consider.
1. Should such a device communicate via modbus or are their other 
alternatives that should be considered?
2. Modubs RTU or TCP/IP?
3. How are modbus devices communicated with before they are programmed with 
a modbus address (eg. is there a standard for programming the modbus ID on 
such devices or is it device specific)?
4. Are there other considerations in relation to communication we should be 
investigating?
I'm sure I will have are other questions that will come to mind or in 
response to any answers but would appreciate any assistance or help with the 
direction I should be looking.
Regards
ilr"
    @ilr: "Thank You Pieter
I really appreciate you advice
a,b) At this stage the device is for use in wineries.  I will have a look at 
fieldbus and profibus to see what they offer.
c) 4-20mA was considered but other information is required from the sensor 
other than just the analogue output as well as a requirement to store 
calibration information.  Are their devices that can be used to control from 
an output such as modubs/fieldbus or profibus rather than using PC hardware 
to control?
d) Ultimately their will be multiple devices throughout the winery for 
measurement and control.
Regards
ilr
"pieter steenekamp" <email_address> wrote in message 
news:<email_address>
<quote>"
    @cdorrough: ""ilr" <email_address> wrote in message 
news:<email_address>
<quote>
For the application you have described, I would suggest you look seriously 
at Profibus <url> - specifically Profibus DP.
If you don't want to use PC hardware, Siemens (Vipa and others) sell small 
footprint PLCs that can communicate using Profibus and control other analog 
and digital devices at the same time.  This equipment is already in common 
use in wineries and breweries world-wide and likely some of your clients 
already use it.
Good luck.
Cameron:-)"
    @ilr: "Thanks to both of you for your assistance.
Sorry for my ignorance but could you clear something up for me.
I know that PLC's in general take an analogue or digital signal (on/off) 
from some kind of sensor or device and then do something based on that 
signal.  Is it common for PLC's to also take a signal from sensors or 
devices that talk modbus, fieldbus, profibus etc. and do something based on 
that value eg PID control (the signal is neither analogue or digital but a 
numerical value)?  Does the PLC act as a "master" device polling the sensor 
at regular intervals or the other way around.  Are these kind of PLC's 
common or am I on the wrong track?
Thanks in advance
"pieter steenekamp" <email_address> wrote in message 
news:<email_address>
<quote>"
    @ilr: "Thanks to both of you for your assistance.
Sorry for my ignorance but could you clear something up for me.
I know that PLC's in general take an analogue or digital signal (on/off)
from some kind of sensor or device and then do something based on that
signal.  Is it common for PLC's to also take a signal from sensors or
devices that talk modbus, fieldbus, profibus etc. and do something based on
that value eg PID control (the signal is neither analogue or digital but a
numerical value)?  Does the PLC act as a "master" device polling the sensor
at regular intervals or the other way around.  Are these kind of PLC's
common or am I on the wrong track?
Thanks in advance
news:<email_address>
<quote>"
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