Skip to Content
Last modified by Mengting Qiu on 2024/09/02 17:23
From version 9.1
edited by Mengting Qiu
on 2024/09/02 16:05
Change comment: Uploaded new attachment "image-20240902160516-1.png", version {1}
To version 5.1
edited by Mengting Qiu
on 2024/09/02 12:01
Change comment: There is no comment for this version

Summary

Details

Page properties
Content
... ... @@ -16,86 +16,70 @@
16 16  In some case, the measurement and real value are in different range, but they are both linear, we have to calculate the real value with the measurement we can use a simple Linear Calibration.
17 17  
18 18  
19 -== 2.1 Solve the linear relationship manually ==
19 +Example: we have a water level probe, the measurement range is 0 ~~ 10 meters, and the output is 4~~20mA, this means the when the water level is 0 meter, the output is 4mA, when the water level is 10 meters, the output is 20mA. We can make a coordinate axis as below:
20 20  
21 +1. Y axis is the real value, from 0 ~~ 10 meters
22 +1. X axis is the probe output , from 4~~20mA
21 21  
22 -(% style="color:blue" %)**Example:**(%%) we have a water level probe, the measurement range is 0 ~~ 10 meters, and the output is 4~~20mA, this means the when the water level is 0 meter, the output is 4mA, when the water level is 10 meters, the output is 20mA.
24 +We use two points to make the linear line: point1(x1,y1) = (4,0), point2(x2,y2)= (20,10). Since the reading is linear, all probe output and real value is on this line, so we can calculate the real value by probe output in two steps:
23 23  
24 -We can make a coordinate axis as below:
26 +Step1: Get k(Slope) for the line: k=(y2-y1)/(x2-x1) = (10-0)/(20-4) =10/16= 0.625
25 25  
26 -1. (% style="color:#4f81bd" %)**Y**(%%) axis is the real value, from 0~~10 meters
27 -1. (% style="color:#4f81bd" %)**X**(%%) axis is the probe output , from 4~~20mA
28 +Step2: Get real value ( y ):
28 28  
29 -We use two points to make the linear line: Point1(x1,y1) = (4,0), Point2(x2,y2)= (20,10).
30 +k=(y-y1)/(x-x1)  
30 30  
31 -Since the reading is linear, all (% style="color:#4f81bd" %)**probe output**(%%) and (% style="color:#4f81bd" %)**real value**(%%) is on this line, so we can calculate the real value by probe output in two steps:
32 +~-~-> y = k*(x-x1)+y1 = 0.625 * (x-4) + 0.
32 32  
33 -* **Step1:** Get (% style="color:#4f81bd" %)**realk(Slope)**(%%) for the line:
34 + ~= 0.625 * (x-4)
34 34  
35 - k=(y2-y1)/(x2-x1) = (10-0)/(20-4) =10/16= 0.625
36 +When x=12mA , y=5 meters
36 36  
37 -* **Step2:** Get (% style="color:#4f81bd" %)**real value( y )**(%%):
38 +When x=8mA, y= 2.5 meters
38 38  
39 - k =(y-y1)/(x-x1)  
40 40  
41 - ~-~-> y = k*(x-x1)+y1 = 0.625 * (x-4) + 0.
42 -
43 - ~= 0.625 * (x-4)
44 -
45 -Thus, we can introduce x-values to the already obtained equations to derive the corresponding y-values：
46 -
47 -When x=12 mA , y=5 meters
48 -
49 -When x=8 mA, y=2.5 meters
50 -
51 -
52 52  A more general formular:
53 53  
54 -(% style="color:#4f81bd" %)**Y=(y2-y1)/(x2-x1)* (x-x1) + y1**
43 +Y=(y2-y1)/(x2-x1)* (x-x1) + y1
55 55  
56 56  
57 -Calibration Curve Schematic：
46 +[[image:image-20240902114541-1.png||height="492" width="874"]]
58 58  
59 -[[image:image-20240902114541-1.png||height="479" width="851"]]
60 60  
61 61  
62 -== 2.2 Performing linear calibration curves in Excel ==
50 += 3. Case examples =
63 63  
64 64  
65 -In addition, we can also perform calibration curves in Excel and directly obtain linear equations by statistics of X and Y values.
53 +Some case for example which we can use Linear Calibration:
66 66  
67 67  
56 +Case 1: Calibrate Microwave Radar Readling.
68 68  
58 +The microwave radar reading might effect by the OUM(Object Under Measured), but the reading still linear. In this case, we can measure the closest(x1,y1) and the farthest point(x2,y2). Where the x is reading in platform, y is the real value. And use above method to calibrate.
69 69  
70 70  
61 +Case 2: Calibrate the Soil EC base on SE01 soil sensor raw EC reading.
71 71  
63 +The SE01 probe is calibrated via mineral soil. The reading for other soil will be different by still in linear, In this case, we can measure two points (x1,y1) and (x2,y2). Where the x is reading of Raw EC, y is the real EC for the soil. And use above method to calibrate
72 72  
73 73  
74 -= 3. Case examples =
66 +Case 3: use water level probe to calibrate for oil.
75 75  
68 +Oil has different density vs water, but we can still use the immersion type water level pressure sensor to get the oil level. In this case, we can measure two points (x1,y1) and (x2,y2). Where the x is reading of water level, y is the oil level. And use above method to calibrate
76 76  
77 -Some case for example which we can use Linear Calibration:
78 78  
71 +Notice for Linear Calibrate:
79 79  
80 -(% style="color:blue" %)**Case 1: Calibrate Microwave Radar Readling.**
73 +1. k(Slope) is very important, We can measure more points to calculate the most accuracy k.
74 +1. Make sure the mapping is linear, and choose two calibrate points as “far” as possible.
81 81  
82 -The microwave radar reading might effect by the OUM(Object Under Measured), but the reading still linear. In this case, we can measure the closest(x1,y1) and the farthest point(x2,y2). Where the x is reading in platform, y is the real value. And use above method to calibrate.
83 83  
84 84  
85 -(% style="color:blue" %)**Case 2: Calibrate the Soil EC base on SE01 soil sensor raw EC reading.**
86 86  
87 -The SE01 probe is calibrated via mineral soil. The reading for other soil will be different by still in linear, In this case, we can measure two points (x1,y1) and (x2,y2). Where the x is reading of Raw EC, y is the real EC for the soil. And use above method to calibrate
88 88  
89 89  
90 -(% style="color:blue" %)**Case 3: use water level probe to calibrate for oil.**
91 91  
92 -Oil has different density vs water, but we can still use the immersion type water level pressure sensor to get the oil level. In this case, we can measure two points (x1,y1) and (x2,y2). Where the x is reading of water level, y is the oil level. And use above method to calibrate
93 93  
94 94  
95 -(% style="color:red" %)**Notice for Linear Calibrate:**
96 96  
97 -1. k(Slope) is very important, We can measure more points to calculate the most accuracy k.
98 -1. Make sure the mapping is linear, and choose two calibrate points as "far" as possible.
99 -
100 -
101 101  
image-20240902160516-1.png
Author
... ... @@ -1,1 +1,0 @@
1 -XWiki.ting
Size
... ... @@ -1,1 +1,0 @@
1 -31.2 KB
Content