Megger CM500 - Basic and Service Error Calculation; Error Calculation Tables

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Basic and service errors for Insulation and Resistance ranges
The basic error is the maximum inaccuracy of the instrument under ideal conditions, whereas the service error is the maximum
inaccuracy taking into effect of battery voltage, temperature, interference, and system voltage and frequency, where applicable.
After determining the service error, we can then calculate the measurement range. This is the range of measurement over which the
error in service is less than 30% of the reading. Digital instruments are affected by the number of digits error - for example a value
0,10Ω measured with the continuity range may give a display in the range 0,07 Ω to 0,13 Ω which is a maximum error of 30%.
Therefore the measurement range measuring low resistance is 0,10 Ω to 99,9 Ω. When checking that a measurement does not exceed
a limit, the service error needs to be taken into account and these tables enables this to be done quickly and easily. These will
guarantee that the value being measured is greater than or less than the limit value specified as appropriate.
Insulation Resistance - MΩ
Continuity / Low Resistance
Ω
Error = 4%+4d
Basic and Service Error Calculation
Limit
0,10
0,15
0,20
0,25
0,30
0,35
0,40
0,45
0,50
0,60
0,70
0,80
0,90
1,00
1,50
2,00
2,50
3,00
3,50
4,00
Min.
Indicated
reading
0,14
0,20
0,25
0,30
0,35
0,40
0,46
0,51
0,56
0,66
0,77
0,87
0,98
1,08
1,60
2,12
2,64
3,16
3,68
4,20
Limit
4,50
5,00
6,00
7,00
8,00
9,00
10,0
15,0
20,0
25,0
30,0
35,0
40,0
45,0
50,0
60,0
70,0
80,0
90,0
Min.
Indicated
reading
4,72
5,24
6,28
7,32
8,36
9,40
10,8
16,0
21,2
26,4
31,6
36,8
42,0
47,2
52,4
62,8
73,2
83,6
94,0
Limit
0,10
0,15
0,20
0,25
0,30
0,35
0,40
0,45
0,50
0,60
0,70
0,80
0,90
1,00
1,50
2,00
2,50
3,00
3,50
4,00
Max.
Indicated
reading
0,06
0,10
0,15
0,20
0,25
0,30
0,34
0,39
0,44
0,54
0,63
0,73
0,82
0,92
1,40
1,88
2,36
2,84
3,32
3,80
Limit
4,50
5,00
6,00
7,00
8,00
9,00
10,0
15,0
20,0
25,0
30,0
35,0
40,0
45,0
50,0
60,0
70,0
80,0
90,0
100
Max.
Indicated
reading
4,28
4,76
5,72
6,68
7,64
8,60
9,56
14,0
18,8
23,6
28,4
33,2
38,0
47,8
47,6
57,2
66,8
76,4
86,0
92,0
Limit
150
200
250
300
350
400
450
500
600
700
800
900
1,00 k
1,50 k
2,00 k
2,50 k
3,00 k
3,50 k
4,00 k
4,50 k
Max.
Indicated
reading
140
188
236
284
332
380
428
476
572
668
764
860
900
1,40 k
1,88 k
2,36 k
2,84k
3,32 k
3,80 k
4,28 k
Limit
5,00 k
6,00 k
7,00 k
8,00 k
9,00 k
Max.
Indicated
reading
5,76 k
5,72 k
6,68 k
7,64 k
8,60 k