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EXCEL 50/100/500/600/800 ATTRIBUTES
EN2B-0092GE51 R0512
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Fig. 20. Trend log display (analog input)
Fig. 21. Trend log display (digital input)
200 values can be written to the local trend log memory. If the memory is full, the
earliest data is overwritten with new data. The 200 most up-to-date values are
always available in the memory.
If several datapoints are selected for the trend log, those datapoints whose value or
status changes more frequently will create a larger number of values to be logged.
Each change in status is logged for digital points. For analog points, there are two
different types of trending: value hysteresis and time-based. The datapoint
attributes for each of these types of trending are described below.
Value Hysteresis
When value hysteresis trending is selected (i.e. when the attribute "Trend Cycle" is
set to 0), a new value is written to the memory when the point changes more than
the given hysteresis compared to the previous value.
The default hysteresis value is 1% of the actual value, but not less than 0.2 (see
also section "Trend Hysteresis" on page 22).
Example 1: The current measured value is 20°C
1 % of 20°C = 0.2°C
A new trend log value is stored at either 20.2°C or 19.8°C
Example 2: The current measured value is 9°C
A new trend log value is stored at either 9.2°C or 8.8°C
The trend can be displayed as text and as a graphic. The graphic display offers the
following features:
• Simultaneous display of an analog and a digital datapoint
• Auto-scaling of the time and the value axis
• Scrolling the time axis
• Manual re-scaling of the time axis (ZOOM/UNZOOM function) with possible
resolutions:
- minute display
- hourly display
- daily display
- weekly display
• Quick change between graphic and text display
Trend Cycle (V2.03.x)
With V2.03.xx firmware, it is possible to perform time-based trending for physical
and pseudo analog points for both local and remote trending. A trend value is
stored in the trend buffer at the end of a fixed interval given by the datapoint
attribute "Trend Cycle", as shown in Fig. 22: