• Not Answered

3051 accuracy

Dear Sirs,

I have question about accuracy, hope someone  can help to figure it out.

What side is right that I should use?

Ex. 3051CD1, accuracy: 0.1% of span, For span less than 15:1, (0.025+0.005(URL/span))% of span.

  1. I think the left side is more reasonable: the measurable sensitivity of the meter should not change because of how many span you use (at least it will not change so large, it should be the problem of electronic digital resolution 2^12).

2. Turndown Ratio:1, URL/span=1, accuracy should be the highest, but Sensitivity is the worst (like right side 0.635mmH2O).

3.For Spans less than 15:1, (0.025+0.005 (URL/span))% of span, meaning turn down ratio is not greater than 15, so formulas are used in Turn down Ratio=<15, so the span should be greater than URL/15=42 mmH2O when using this formula (left form).

Left side Left side Left side Left side Right side Right side Right side Right side
URL 635.000 mmH2O LRL -635 Minimum Span 12.70 mmH2O
0.1% of Span For Spans less than 15:1 (0.025+0.005(URL/Span))% of span
Turndown ratio Accuracy % Span sensitivity Turndown ratio Accuracy % Span sensitivity
1 0.030 635.00 0.191 1 0.1 635.00 0.635
2 0.035 317.50 0.111 2 0.1 317.50 0.318
3 0.040 211.67 0.085 3 0.1 211.67 0.212
4 0.045 158.75 0.071 4 0.1 158.75 0.159
5 0.050 127.00 0.064 5 0.1 127.00 0.127
6 0.055 105.83 0.058 6 0.1 105.83 0.106
7 0.060 90.71 0.054 7 0.1 90.71 0.091
8 0.065 79.38 0.052 8 0.1 79.38 0.079
9 0.070 70.56 0.049 9 0.1 70.56 0.071
10 0.075 63.50 0.048 10 0.1 63.50 0.064
11 0.080 57.73 0.046 11 0.1 57.73 0.058
12 0.085 52.92 0.045 12 0.1 52.92 0.053
13 0.090 48.85 0.044 13 0.1 48.85 0.049
14 0.095 45.36 0.043 14 0.1 45.36 0.045
15 0.100 42.33 0.042 15 0.1 42.33 0.042
16 0.100 39.69 0.040 16 0.105 39.69 0.042
17 0.100 37.35 0.037 17 0.11 37.35 0.041
18 0.100 35.28 0.035 18 0.115 35.28 0.041
19 0.100 33.42 0.033 19 0.12 33.42 0.040
20 0.100 31.75 0.032 20 0.125 31.75 0.040
21 0.100 30.24 0.030 21 0.13 30.24 0.039
22 0.100 28.86 0.029 22 0.135 28.86 0.039
23 0.100 27.61 0.028 23 0.14 27.61 0.039
24 0.100 26.46 0.026 24 0.145 26.46 0.038
25 0.100 25.40 0.025 25 0.15 25.40 0.038
26 0.100 24.42 0.024 26 0.155 24.42 0.038
27 0.100 23.52 0.024 27 0.16 23.52 0.038
28 0.100 22.68 0.023 28 0.165 22.68 0.037
29 0.100 21.90 0.022 29 0.17 21.90 0.037
30 0.100 21.17 0.021 30 0.175 21.17 0.037
31 0.100 20.48 0.020 31 0.18 20.48 0.037
32 0.100 19.84 0.020 32 0.185 19.84 0.037
33 0.100 19.24 0.019 33 0.19 19.24 0.037
34 0.100 18.68 0.019 34 0.195 18.68 0.036
35 0.100 18.14 0.018 35 0.2 18.14 0.036
36 0.100 17.64 0.018 36 0.205 17.64 0.036
37 0.100 17.16 0.017 37 0.21 17.16 0.036
38 0.100 16.71 0.017 38 0.215 16.71 0.036
39 0.100 16.28 0.016 39 0.22 16.28 0.036
40 0.100 15.88 0.016 40 0.225 15.88 0.036
41 0.100 15.49 0.015 41 0.23 15.49 0.036
42 0.100 15.12 0.015 42 0.235 15.12 0.036
43 0.100 14.77 0.015 43 0.24 14.77 0.035
44 0.100 14.43 0.014 44 0.245 14.43 0.035
45 0.100 14.11 0.014 45 0.25 14.11 0.035
46 0.100 13.80 0.014 46 0.255 13.80 0.035
47 0.100 13.51 0.014 47 0.26 13.51 0.035
48 0.100 13.23 0.013 48 0.265 13.23 0.035
49 0.100 12.96 0.013 49 0.27 12.96 0.035
50 0.100 12.70 0.013 50 0.275 12.70 0.035

2 Replies

  • Your right side calculations are the correct interpretation of our reference accuracy specification. Apply a 0.1% of calibration span uncertainty, until you reach a 15:1 turn-down, or 42.33 mmH2O calibrated span. Then the uncertainty as a percent of span increases according to the equation.
    I checked a handful of your numbers in the right-hand column, and it appears you are performing the calculations correctly.
  • Thank you in advance.
    How can you explain the sensitivity? Is it reasonable the turndown ratio bigger cause more sensitivity?

    Thank you,
    Lin Chun Hung