Hello guys,
I am looking for a data acquisition board which can gather signal from EMC (equilibrium moisture content), temprature and MC (moisture content) sensors to measure moisture of lumbers and temprature inside the drying kiln. This acquisition board should be able to give out analog values of temprature and moisture or use RS232 or RS485 interface to deliver these information to PLC controller.
Can anybody advise me some devices like that ?

 

Perhaps some clarification:

Data acquisition boards ACCEPT signals from sensors, transmitters or transducers which are the devices that do the measurement of temperature or moisture and produce an electrical signal that can be used for recording or control.

Data acquisition boards are not capable of making measurements themselves. Your PLC could effectively the "front end" for a data acquisition system. The front end takes in the analog signals from the field devices that do the measurements. Data acquisition boards serve as a front end for a PC. But you already have a PLC, which presumably you are going to use for control.

The field measurments, like temperature measurements, are typically done with RTDs or thermocouples. PLCs need specific analog input boards for these signals. Sometimes the RTD or thermocouples are connected to a 'transmitter' and the transmitter sends the signal to the PLC. This is done for long distance wire runs.

Moisture measurements can be simple relative humidity (RH), dew point, or absolute measurements, or done with moisture analyzers. I use Rotronics brand.

PLCs do not do a good job of storing data so you can analyze it. Stand alone recorders do, or there is HMI software with "historian" modules that are designed to record data and display trended data. (which is what data acquisition boards. Wonderware, Intellution, Citect are HMI brand names (along with 100 others) and most PLCs have a an-nhouse package, too.

You might have to find an "instrumentation distributor" who is familiar with process control, if your PLC vendor is into discrete control and not familiar with the analog end of process control.

David