WHITE BROWN DA 918 Uživatelský manuál stáhnout pdf (Strana 72)

NI cDAQ-918x/919x User Manual

Counter Input Applications

The following sections list the various counter input applications available on the cDAQ chassis:

• Counting Edges

• Pulse-Width Measurement

• Pulse Measurement

• Semi-Period Measurement

• Frequency Measurement

• Period Measurement

• Position Measurement

Counting Edges

In edge counting applications, the counter counts edges on its Source after the counter is armed.

You can configure the counter to count rising or falling edges on its Source input. You also can

control the direction of counting (up or down), as described in the Controlling the Direction of

Counting section. The counter values can be read on demand or with a sample clock.

Refer to the following sections for more information about edge counting options:

• Single Point (On-Demand) Edge Counting

• Buffered (Sample Clock) Edge Counting

Single Point (On-Demand) Edge Counting

With single point (on-demand) edge counting, the counter counts the number of edges on the

Source input after the counter is armed. On-demand refers to the fact that software can read the

counter contents at any time without disturbing the counting process. Figure 5-2 shows an

example of single point edge counting.

Figure 5-2. Single Point (On-Demand) Edge Counting

Buffered Position No Yes

Buffered Two-Signal Edge Separation Yes Yes

Table 5-1. Counter Timing Measurements (Continued)

Measurement

Implicit

Timing Support

Sample Clocked

Timing Support

Counter Armed

SOURCE

Counter Value105432

1 2 ... 67 68 69 70 71 72 73 74 75 76 77 ... 126 127

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