National Instruments BridgeVIEW 用户手册
Chapter 4
Human Machine Interface
4-30
© National Instruments Corporation
Figure 4-5. Two Trend Display VI
The real-time trend indicator updates with a value for each tag every time
the indicator is written to. If a VI using this indicator is executed several
times, it still has previous data displayed. For this reason, you might want
to initialize the real-time trend indicator before the loop begins execution.
You also can control attributes of the real-time trend indicator such as time
scale. Figure 4-6 shows a single real-time trend display VI that initializes
the time scale of the Trend indicator to the current time (read from Get Date
Time in Seconds) and the interval corresponding to the Trend Tags time
interval input. It also clears the trend display by writing an empty array to
the Trends History Data attribute.
the indicator is written to. If a VI using this indicator is executed several
times, it still has previous data displayed. For this reason, you might want
to initialize the real-time trend indicator before the loop begins execution.
You also can control attributes of the real-time trend indicator such as time
scale. Figure 4-6 shows a single real-time trend display VI that initializes
the time scale of the Trend indicator to the current time (read from Get Date
Time in Seconds) and the interval corresponding to the Trend Tags time
interval input. It also clears the trend display by writing an empty array to
the Trends History Data attribute.
Figure 4-6. Initializing the Waveform Chart Indicator for a Real-Time Trend Display