National Instruments NI 6612 User Manual

3-14 | ni.com
Chapter 3 Counters
• CI.CtrTimebase.Src—To change the signal used as the counter timebase, set this property
to a different terminal.
Sample Clock (without Averaging)
With this method, for each sample clock the counter detects the last full period of the
signal-to-measure that occurs before the sample clock. The counter measures the duration of this
one period by counting the number of cycles (T2) of the timebase.
At each sample clock, the device stores T2 in a buffer. DAQmx reads this value, and uses the
known frequency of the timebase (f
k
), to calculate the frequency of the input signal (f
x
) as:
Figure 3-16. Frequency Measurement: Sample Clock without Averaging
To use the Sample Clock (without Averaging) method, configure the following:
• DAQmx Create channel (CI-Frequency)—Use this VI or function to create the channel.
• DAQmx Timing (Sample Clock)—Use this VI or function to set the number of samples,
samples clock source, and other properties.
• CI.Freq.EnableAveraging—Set this property to False.
By default, the counter measures the frequency on a default PFI terminal (refer to Chapter 5,
Counter Signal Routing and Clock Generation, for more information) and use an onboard
100 MHz clock as the timebase. To change the signals used for this measurement, configure the
following:
• CI.Freq.Term—The signal-to-measure comes from an input terminal. To change the
signal-to-measure, set this property to a different terminal.
• CI.CtrTimebase.Src—To change the signals used as the counter timebase, set this
property to a different terminal.
f
x
f
k
1
T2
------×=
Sample
Clock
DAQmx
Start Task
Buffer
6
646
4
6
4
6
6
Sample 1 Sample 2 Sample 3
Signal to
Measure (f )
Counter
Timebase (f )
x
k

National Instruments NI 6612 Specifications

General

Product Name	National Instruments NI 6612
Category	Computer Hardware
Digital I/O Channels	32
Maximum Counter Frequency	80 MHz
Input Voltage Range	0 V to 5 V
Maximum Output Current	±24 mA
Maximum Clock Rate	80 MHz
Interface	PCI
Operating System Compatibility	Windows
Output Voltage	5 V
Output Current	24 mA
Counter/Timers	4
Digital I/O Logic Levels	TTL
Number of Channels	32

Summary

Important Information

Warranty and Legal

Covers product warranty, copyright, EULAs, and legal notices.

Safety and Product Warnings

Details critical safety warnings and product usage limitations.

Chapter 1 Introduction

Getting Started and Accessories

Guides on installation, accessories, and initial device setup.

Chapter 2 Digital I/O

Digital I/O Operations

Explains input/output methods, timing, and waveform acquisition/generation.

Digital I/O Configuration and Protection

Covers digital filtering, I/O protection, and signal connection.

Chapter 3 Counters

Counter Input Measurements

Details measurement tasks like edge counting, pulse, frequency, and encoders.

Counter Output Generation

Covers pulse and waveform generation using counters.

Chapter 4 PFI

PFI Signal Usage

Explains PFI configuration for timing, digital I/O, and detection.

PFI Filters and Signal Integrity

Discusses PFI filtering, I/O protection, and signal integrity.

Chapter 5 Counter Signal Routing and Clock Generation

Clock Sources and Routing

Describes clock sources, timebases, and signal routing for counters.

Device Synchronization

Explains synchronizing multiple devices using PXIe, PCI, and RTSI.

Chapter 6 Bus Interface

Data Transfer and PXI Express

Details data transfer methods like DMA and PXI Express considerations.

Chapter 7 Calibration

Calibration Information

States that calibration is not required for the NI 6612.

Appendix A Pinout and Signal Descriptions

NI 6612 Pinout Details

Provides detailed pinout information and signal descriptions for the device.

Appendix B Technical Support and Professional Services

NI Support and Services

Lists resources for technical support, training, and professional services.