5 standard computation functions, Standard computation functions -16, Difference between channels – Yokogawa DR240 User Manual
Page 42: Linear scaling, Moving average
2-16
IM DR232-01E
2.5
Standard Computation Functions
Standard computations such as difference between channels and linear scaling can be set with
measurement input settings. A moving average computation is also available.
Difference between Channels
This function conputes the difference between the measurement values of a selected channel
(=reference channel) and any other channel (=destination channel). This can be applied to each
channel in the same unit. The computation formula is as follows:
Result of difference between channels computation = measurement value of destination
channel — measurement values of reference channel
Linear Scaling
This function changes the left and right span of the recording span to left and right scale values
which are converted to a different physical quantity. This can be applied to each channel and a
different engineering unit can be entered for display and printouts.
Example where voltage values are cenverted into linear scaling values
Left span:-2V
(=left scale:-0.1A)
Right span:2V
(=Right scale:1.1A)
Moving Average
This function computes a moving average over a preset number of (K) measurement values. This
function is useful for displaying and recording of unsteady measurement values. The computation
formula is as follows.
D
m
= (M
m
-
(K-1)
+ M
m
-
(K-2)
+ ... + M
m
-
2
+M
m
-
1
+ M
m
) / K
where
D
m
: “m”th average value
M
m
-
(K-1)
: the measurement value of the “K-1”th measurement before the “m”th
measurement
M
m
-
(K-2)
: the measurement value of the “K-2”th measurement before the “m”th
measurement
.
.
.
.
M
m
-
2
: the measurement value of the second last measurement before the “m”th
measurement
M
m
-
1
: the measurement value of the last measurement before the “m”th measurement
M
m
: the measurement value of the “m”th measurement
K
: number of samples, and an integer ranging from 2 to 64
At the first computation, the measurement value of the first measurement will be multiplied by
the number of samples, after which the average will be taken. The measurement values of the
second and later measurements will replace these in turn, after which the average will be
calculated each time.