National Instruments cDAQ-9185 User Manual

6-4 | ni.com
Chapter 6 Counters
• 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 6-2 shows an
example of single point edge counting.
Figure 6-2. Single Point (On-Demand) Edge Counting
You also can use a pause trigger to pause (or gate) the counter. When the pause trigger is active,
the counter ignores edges on its Source input. When the pause trigger is inactive, the counter
counts edges normally.
You can route the pause trigger to the Gate input of the counter. You can configure the counter
to pause counting when the pause trigger is high or when it is low. Figure 6-3 shows an example
of on-demand edge counting with a pause trigger.
Figure 6-3. Single Point (On-Demand) Edge Counting with Pause Trigger
Counter Armed
SOURCE
Counter Value105432
Counter Armed
SOURCE
Pause Trigger
(Pause When Low)
Counter Value
100 5432
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National Instruments cDAQ-9185 Specifications

General

Number of Slots	8
Maximum Data Transfer Rate	1 GB/s
Supported Modules	C Series I/O Modules
Chassis Type	CompactDAQ
Operating Temperature	0 °C to 55 °C
Storage Temperature	–40 °C to 70 °C
Weight	0.771 kg
Timing	IEEE 1588 Precision Time Protocol (PTP)
Synchronization	IEEE 1588 Precision Time Protocol (PTP)

Summary

Getting Started with the cDAQ Chassis

Safety Guidelines

Important safety information and precautions for operating the cDAQ chassis.

Installing the cDAQ Chassis

Steps and instructions for installing the cDAQ chassis.

Wiring External Power to the cDAQ Chassis

Procedure for connecting an external power source to the cDAQ chassis.

Mounting the cDAQ-9185/9189

Guidelines for mounting the cDAQ chassis for optimal performance.

Analog Input

Analog Input Triggering Signals

Information on start, reference, and pause trigger signals for analog input.

Analog Input Timing Signals

Details on AI sample clock, timebase, and start trigger signals.

AI Start Trigger Signal

Analog Output

Analog Output Data Generation Methods

Analog Output Triggering Signals

Analog Output Timing Signals

AO Start Trigger Signal

Digital Input/Output and PFI

Digital Input/Output

Using digital I/O with C Series modules and specifications.

Digital Input

Acquiring digital waveforms using parallel or serial digital modules.

Digital Input Triggering Signals

Digital Output

Generating digital output with C Series modules and specifications.

Counters

Counter Timing Engine

Counter Triggering

Counting Edges

Pulse-Width Measurement