UMAX030211 Version 1.0.2. Preliminary Documentation – May be subject to change
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2.4.1.
X‐Axis, Input Data Response
In the case where the “
X-Axis Type
” =
‘Data Response’,
the points on the X-Axis represents the
data of the control source.
The constraint on the X-Axis data is that the next index value is greater than or equal to the one
below it, as shown in the equation below. Therefore, when adjusting the X-Axis data, it is
recommended that X
11
is changed first, then lower indexes in descending order.
MinInputRange <= X
1
<= X
2
<= X
3
<= X
4
<= X
5
<= X
6
<= X
7
<= X
8
<= X
9
<= X
10
<= X
11
<= MaxInputRange
As stated earlier, MinInputRange and MaxInputRange will be determined by the scaling objects
associated with X-Axis Source that has been selected, as outlined in Table 24.
2.4.2.
Y‐Axis, Lookup Table Output
By default, it is assumed that the output from the lookup table function block will be a percentage
value in the range of 0 to 100.
In fact, so long as all the data in the Y-Axis is 0<=Y[i]<=100 (where i = 1 to 11) then other function
blocks using the lookup table as a control source will have 0 and 100 as the Scaling 1 and Scaling
2 values used in linear calculations shown in Table 24.
However, the Y-Axis has no constraints on the data that it represents. This means that inverse or
increasing/decreasing or other responses can be easily established. The Y-Axis does not have to be
a percentage output but could represent full scale process values instead.
In all cases, the controller looks at the entire range of the data in the Y-Axis sub-indexes and selects
the lowest value as the MinOutRange and the highest value as the MaxOutRange. So long as they
are not both within the 0 to 100 range, they are passed directly to other function blocks as the limits
on the lookup table output. (i.e. Scaling 1 and Scaling 2 values in linear calculations.)
Even if some of the data points are
‘Ignored’
as described in Section2.4.3, they are still used in the
Y-Axis range determination. If not all the data points are going to be used, it is recommended that
Y10 be set to the minimum end of the range, and Y11 to the maximum first. This way, the user can
get predictable results when using the table to drive another function block, such as an analog output.
2.4.3.
Point to Point Response
By default, all six lookup tables have a simple linear response from 0 to 100 in steps of 10 for both
the X and Y axes. For a smooth linear response, each point in the 30z5h
LTz Point Response
array
is setup for a
‘Ramp To’
output.
Alternatively, the user could select a
‘Step To’
response for 30z4h, where N = 2 to 11. In this case,
any input value between X
N-1
to X
N
will result in an output from the lookup table function block of Y
N
.
(Recall: LTz Point Response sub-index 1 defines the X-Axis type)
Figure 13 shows the difference between these two response profiles with the default settings.
