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2408
i Indicator Engineering Manual
4.5.7 Peak Hold and Sample and Hold
Peak Hold logs the maximum and minimum values that the indicator reads during a particular process. The peak
hold value can be displayed as the main front or back display parameter, as described in section 2.1.2.
Sample and Hold logs the reading at the moment that the digital input becomes true.
Both functions are initiated by turning digital input 1 or digital input 2 to ON. They are edge triggered, so to reset
and re-start, the input must be turned OFF and ON again, as detailed in Figure 4.5 below.
The values may be read in two ways:-
1. From Information List
<
inFo
>
as:-
LoG.L Minimum process variable
LoG.H Maximum process variable
LoG.A Average process variable
These values are reset when the parameter < rES.L > in the < inFo > list is turned to < YES >, or the indicator power
is cycled.
2. Maximum and minimum values can be promoted to the main front or back display as <
PV.Hi
> or <
PV.Lo
>,
see section 2.1.2. They are reset when the power to the controller is cycled or by setting the values of
<
LoG.L
> and <
LoG.H
> to zero in the <
inFo
> list.
Figure 4-5: Action of Sample and Hold and Peak Hold
Digital input
LA or LB
ON
OFF
PV
Sample and Hold
Peak Hold
Restart Set
Time
PV
Peak Hold does
not read this
point since the
digital input is
not set
Average PV
<
LoG.A
>
Maximum PV
<
LoG.H
>
Minimum PV
<
LoG.L
>
Part Number HA027240 Issue 5.0 Feb 2015
45