adccommunitymod (AutomationDirect) asked a question.
Converting a 4-20ma to a negative number
Created Date: April 28,2008
Created By: couv1
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I am using a DL05 CPU and a F0-4AD2DA-1 analog module. I am reading a 4-20mA signal from a dewpoint sensor. The 4-20 signal represents a value of -85 F to +68 F. I am unclear on how to deal with these values within the PLC. Other programs I have written strictly deal with a positive value and anything below zero is ignored. On this particular application I need to set a bit when the sensor reaches -40 deg F. I am also displaying the value of the humidity sensor on a C-More micro.
Created Date: May 01,2008
Created by: couv1
Thank you - MacS
That seems to work just fine.
I have ran into another issue though with changing the setpoint for the C10 coil.
Originally we wanted to set the bit at -40, but now we would like to change the setpoint through the C-More Micro.
I have the numeric entry in the Cmore set as a signed int 16 (V2040).
How can I take the value of V2040 and use it for the setpoint?
Right now I can only get the Cmore to display is 256 and the PLC is reading 100.
Looks like I need to convert the signed decimal entry to HEX, but not sure how?
Created Date: May 01,2008
Created by: couv1
Thanks again MacS.
One last question....
On certain situations I may need to change the scaling of the analog input to eng units of -184 to +68F.
Is there an easy reference for finding these decimal values (or any decimal value) in hex?
Created Date: May 01,2008
Created by: MacS
Windows Calculator can do number systems conversions. Calculator must in Scientific mode (Select 'View '/'scientific ').
See the radio keys marked Hex,Dec,Oct,Bin.
To convert from decimal to hex:
- Select 'dec ' radio key
- Enter decimal value to convert
- Select 'Hex ' radio key
- Value is converted to hex
Created Date: May 01,2008
Created by: couv1
Escellent!
I think I am all good to go.
Thanks for your help.
Created Date: May 01,2008
Created by: KPrice
couv1, when I don't have a calculator handy, I use the DirectSOFT Memory Editor under Tools and use the Radio Buttons to switch formats and data size. I use any V-memory and just don't save to disk.
Created Date: April 28,2008
Created by: couv1
I am using a DL05 CPU and a F0-4AD2DA-1 analog module. I am reading a 4-20mA signal from a dewpoint sensor. The 4-20 signal represents a value of -85 F to +68 F.
I am unclear on how to deal with these values within the PLC. Other programs I have written strictly deal with a positive value and anything below zero is ignored.
On this particular application I need to set a bit when the sensor reaches -40 deg F.
I am also displaying the value of the humidity sensor on a C-More micro.