InstrumentationUK
Member
Hi Group,
I used the scaling block in RSlogix5K to display PT100 on HMI but the problem is, every time when I measure the resistance across the sensor and do manual calculation it does not match with the scaled value from RSlogix.
( Please find the attached screen shot of RSlogix Scaling block)
Manual calculation:
How I derived at the formula, Temperature= ( 100- measured resistance)/0.384 ?
PT100 data from its data sheet
Transmitter : 4~20mA Output,
Range: -50/250 Deg C
Detector Element Resistance Value :100 ohms at 0°C
According to data given by, the probe is 100 ohms at 0 DegC and 1 DegC change will cause 0.384 change is resistance ( Ref: http://www.picotech.com/applications/pt100.html ).
So
1DegC change = 0.384 ohms
Now for Example, if measured resistance is 115 ohms then
=>15.09 +100 = 115 ohms ( because 100 ohms at 0DC)
=> (100-115)/0.384 = 39.05 Deg C
I have scaled the sensor in Rslogix as per the data provided, which is -50/250 @4/20 mA and I am getting reading as 37.9 DC
After this, I changed the parameters in RSlogix scaling block to match with the manually calculated value and again after a while when I measure the resistance value and do the manual calculation, the calculated value does not match with the value from RSlogix scaling.
Can anyone please tell me where I am making mistake or please tell me what is the best way to do scaling of PT100 in RSlogix5000.
Thanks for the help in advance.
I used the scaling block in RSlogix5K to display PT100 on HMI but the problem is, every time when I measure the resistance across the sensor and do manual calculation it does not match with the scaled value from RSlogix.
( Please find the attached screen shot of RSlogix Scaling block)
Manual calculation:
How I derived at the formula, Temperature= ( 100- measured resistance)/0.384 ?
PT100 data from its data sheet
Transmitter : 4~20mA Output,
Range: -50/250 Deg C
Detector Element Resistance Value :100 ohms at 0°C
According to data given by, the probe is 100 ohms at 0 DegC and 1 DegC change will cause 0.384 change is resistance ( Ref: http://www.picotech.com/applications/pt100.html ).
So
1DegC change = 0.384 ohms
Now for Example, if measured resistance is 115 ohms then
=>15.09 +100 = 115 ohms ( because 100 ohms at 0DC)
=> (100-115)/0.384 = 39.05 Deg C
I have scaled the sensor in Rslogix as per the data provided, which is -50/250 @4/20 mA and I am getting reading as 37.9 DC
After this, I changed the parameters in RSlogix scaling block to match with the manually calculated value and again after a while when I measure the resistance value and do the manual calculation, the calculated value does not match with the value from RSlogix scaling.
Can anyone please tell me where I am making mistake or please tell me what is the best way to do scaling of PT100 in RSlogix5000.
Thanks for the help in advance.