MaGoOoDy
Member
this is one of the assignment that i have been given in my training course, i really don't understand the way to do the calculation required for the calculation ( but the instructor himself provided to us for the sake to concentrate in the programming )
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This system is at the bottom of a coal mine, and it’s measuring the concentration of O2 in the air. The O2 sensor degrades over time and requires calibration by comparing its readings to
known values. Our sensor will read from 0‐40%.
We have calibration gases which are exactly 0% and 30% O2.
Our machine will have two cycles: sampling and calibration. When it’s sampling, it just measures the O2 concentration of the air passing by the sensor.
When we go into a calibration cycle, it needs to open the 0% gas valve and sample it for 30 seconds.
Next it will close the 0% and open the 30% and sample that for 30 seconds. Finally, it will use the average readings it took over those two periods and use them to “tune” its own scaling parameters.
CALIBRATION CALCULATIONS:
Input Min = O2_Zero_Average
Input Max = ( ( O2_Maximum_ Concentration / O2_Calibration_Gas_Concentration ) *
( O2_Test_Gas_Average ‐ O2_Zero_Average ) ) + O2_Zero_Average
O2_Maximum_ Concentration = 40(%)
O2_Calibration_Gas_ Concentration = 30(%)
O2_Test_Gas_Average = average reading sampled during 30% gas period
O2_Zero_Average = average reading sampled during 0% gas period
my inputs as of now :
N7:0 ‐ O2 sensor input signal
B3:0/0 ‐ Calibrate button
O:0/0 ‐ 0% gas valve (energize open)
O:0/1 ‐ 30% gas valve (energize open)
N7:1 ‐ Measured O2 concentration
N7:2 ‐ O2 input min (for SCP instruction, default value = 0)
N7:3 ‐ O2 input max (for SCP instruction, default value = 16383)
* i am using the sensor reading in N7:0 instead of analog channel only for the purpose of the simulation ( i don't have the device now )
my questions are :
- what i have done so far, i have figured out that the sampling could be done using FIFO instruction and 30 seconds timer to calculate the average. but how i will tune the SCP parameters ?????
- is this only the way to calibrate the sensors in PLC ( only through programming ) ?
- as far as i know we have to types of sensor, 2 wires and 4 wires type , is this applicable for both ?
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This system is at the bottom of a coal mine, and it’s measuring the concentration of O2 in the air. The O2 sensor degrades over time and requires calibration by comparing its readings to
known values. Our sensor will read from 0‐40%.
We have calibration gases which are exactly 0% and 30% O2.
Our machine will have two cycles: sampling and calibration. When it’s sampling, it just measures the O2 concentration of the air passing by the sensor.
When we go into a calibration cycle, it needs to open the 0% gas valve and sample it for 30 seconds.
Next it will close the 0% and open the 30% and sample that for 30 seconds. Finally, it will use the average readings it took over those two periods and use them to “tune” its own scaling parameters.
CALIBRATION CALCULATIONS:
Input Min = O2_Zero_Average
Input Max = ( ( O2_Maximum_ Concentration / O2_Calibration_Gas_Concentration ) *
( O2_Test_Gas_Average ‐ O2_Zero_Average ) ) + O2_Zero_Average
O2_Maximum_ Concentration = 40(%)
O2_Calibration_Gas_ Concentration = 30(%)
O2_Test_Gas_Average = average reading sampled during 30% gas period
O2_Zero_Average = average reading sampled during 0% gas period
my inputs as of now :
N7:0 ‐ O2 sensor input signal
B3:0/0 ‐ Calibrate button
O:0/0 ‐ 0% gas valve (energize open)
O:0/1 ‐ 30% gas valve (energize open)
N7:1 ‐ Measured O2 concentration
N7:2 ‐ O2 input min (for SCP instruction, default value = 0)
N7:3 ‐ O2 input max (for SCP instruction, default value = 16383)
* i am using the sensor reading in N7:0 instead of analog channel only for the purpose of the simulation ( i don't have the device now )
my questions are :
- what i have done so far, i have figured out that the sampling could be done using FIFO instruction and 30 seconds timer to calculate the average. but how i will tune the SCP parameters ?????
- is this only the way to calibrate the sensors in PLC ( only through programming ) ?
- as far as i know we have to types of sensor, 2 wires and 4 wires type , is this applicable for both ?