adccommunitymod (AutomationDirect) asked a question.
How do i read temperature with Click PLC
Created Date: September 30,2010
Created By: Jeff S
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Brand spanking new to PLC's and trying to figure out what I need to be able to read temperatures with a Click PLC. I currently have some C0-00DR-D PLC's. I am using RTD's in boilers and need to read between 90 and 110 f. and 120-160 f on two diffent inputs. Adv(thanks)ance Jeff
Created Date: September 30,2010
Created by: bcarlton
First you'll have to get one of the Click PLCs which have analog inputs.
Created Date: September 30,2010
Created by: Jeff S
C002DR-D ? will the PLC read the inputs directly or will the signal need to be converted, I guess is what I am after...
Created Date: September 30,2010
Created by: bcarlton
The inputs of your unit reads On/Off (digital) states only. If you want a numeric value as a temperature then you must use other means. The analog inputs can receive a varying input and convert its level to a number (Analog - To - Digital or A/D). The number can then be used in math calculations and comparisons.
Whether the device which is used to measure the temperature can connect directly to the Click or need intermediate conditioning/amplification is dependent on the type of device.
Created Date: September 30,2010
Created by: milldrone
Bernie,
Couldn't he use some of the solo controllers with a com port? He would also need a rs232 to rs485 converter.
Created Date: September 30,2010
Created by: bcarlton
Yes, I think he has the idea that it will take more than just the digital inputs to process temperature as anything more than On/Off.
Created Date: October 01,2010
Created by: Jeff S
Yea, i see now. thanks for the help. Going to order an anolog unit, and I am certain I will have more questions. The system is basically 11 large boilers. The input temp needs to be maintained at 105 deg for the boiler to run correctly.
I have accuators to replace the manual handles used to adjust input temps now.
The boilers have onboard high limit, and thermostats, so I am just trying to control the input bypass that regulates incoming water temp.
Thanks Guys!
Created Date: October 01,2010
Created by: Kristjan H
Jeff S, the analog Click can not read RTD directly. They only read 4-20mA and 0-5V signals. You can use a transducer to convert the RTD to either of these signals. That way you can connect to the Click.
FYI, the DirectLogic PLCs all have optional RTD modules and you can connect the RTD directly.
Created Date: October 01,2010
Created by: Tinker
Bernie,
Couldn't he use some of the solo controllers with a com port? He would also need a rs232 to rs485 converter.
That would be my first idea too, except that I would use an alalog CLICK that has RS485 since the price difference between the CLICK discrete and analog is less than a 232 to 485 converter. Having the analog also allows the option of using signal conditioners to convert the RDT to 4-20ma and input directly to the CLICK which would make programing easier, however, sometimes a SOLO is actualy less expensive than a conditioner, plus one gets a display and a controller in the same package, also there are only two analog inputs but one could conect quite a few SOLOS if one needed to
Created Date: October 06,2010
Created by: mmprestine
Thermistor
Just get a 10k ohm thermistor and use a voltage divider witha 10k resistor connected to the 0-5vdc analog input. The serial ports on the clicks have a 5vdc reference so you can get it from there. Here is a thermistor for $38.
http://www.omega.com/ppt/pptsc.asp?ref=TH-10-44000&Nav=temd03
Created Date: October 07,2010
Created by: Jeff S
I already have the converters for the RTD's but I like to keep it simple, will try a thermistor on the anolog inputs, hoping to do 3 boilers per PLC
Will the C0-02dd1 do what I need?
Thanks again for your help