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47DT OPERATING MANUAL EM-9508-B Rev.7
21. DETECTING STEEP INPUT CHANGES
Only steep changes in the input signals can be detected with mild changes disregarded, which is called high-pass filter.
Deviation between the currently measured input value and the average of the past values is calculated.
Table 2 shows the relationship between the sampling time and the reading.
■
TABLE 1: HIGH-PASS FILTER
MAIN DISPLAY
FUNCTION
DEFAULT VALUE
High-pass filter OFF
High-pass filter ON
■
TABLE 2: SAMPLING TIME V.S. READING
SAMPLING TIME
INPUT
READING
REFERENCE USED IN NEXT CALCULATION
1
I
1
I
1
– I
1
= 0
C
1
= I
1
2
I
2
I
2
– C
1
C
2
=
1
(C
1
+ I
2
) =
1
(I
1
+ I
2
)
2
2
3
I
3
I
3
– C
2
C
3
=
1
(C
2
+ I
3
) =
1
(I
1
+ I
2
) +
1
I
3
2
4
2
4
I
4
I
4
– C
3
C
4
=
1
(C
3
+ I
4
) =
1
(I
1
+ I
2
) +
1
I
3
+
1
I
4
2
8
4
2
:
:
:
:
n
I
n
I
n
– C
n-1
C
n
=
1
(I
1
+ I
2
) =
1
I
3
+ …… +
1
I
n
2
n-1
2
n-2
2
I
n
: Input
C
n
: Reference value used in the next round of calculation
*
1 Comparison is made against the result of last display (calculated) value.
• EXAMPLE (TABLE 3)
SAMPLING TIME
INPUT
READING
REFERENCE USED IN NEXT CALCULATION
1
5.0
5.0 – 5.0 = 0
5.0
2
4.0
4.0 – 5.0 = -1.0
1
(5.0 + 4.0) = 4.5
2
3
5.5
5.5 – 4.5 = 1.0
1
(4.5 + 5.5) = 5.0
2
4
4.0
4.0 – 5.0 = -1.0
1
(5.0 + 4.0) = 4.5
2
5
9.5
9.5 – 4.5 = 5.0
1
(4.5 + 9.5) = 7.0
2
*
2 Analog output may not simply increase/decrease depending upon timing of the input supplied in relation to the sampling rate.
