NI 6624 Calibration Procedure

NI 6624 Calibration Procedure
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ni.com/manuals
This document contains information for calibrating the National
Instruments 6624 counter/timer device. For more information about
calibration, visit ni.com/calibration.
Contents
Conventions ............................................................................................ 2
Software Requirements ........................................................................... 2
Documentation Requirements................................................................. 2
Calibration Interval ................................................................................. 3
Test Equipment ....................................................................................... 3
Test Conditions ....................................................................................... 4
Device Pinout .......................................................................................... 5
Calibration Process ................................................................................. 6
Initial Setup...................................................................................... 7
Verification ...................................................................................... 8
Where to Go for Support......................................................................... 9
Conventions
The following conventions are used in this document:
This icon denotes a note, which alerts you to important information.
italic
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to a key concept. Italic text also denotes text that is a placeholder for a word
or value that you must supply.
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variables, filenames, and extensions.
Software Requirements
Calibrating the NI 6624 requires installing NI-DAQmx 7.5 or later on the
calibration system. You can download NI-DAQmx at ni.com/downloads.
NI-DAQmx supports programming an External Calibration in the LabVIEW,
LabWindows™/CVI™, Microsoft Visual C++ 6.0, Microsoft Visual
Basic 6.0, Microsoft .NET, and Borland C++ application development
environments (ADEs). When you install NI-DAQmx, you only need to install
support for the ADE that you intend to use.
NI recommends that you install the NI-DAQmx driver software before installing the
NI 6624 device.
Note
Documentation Requirements
For information about NI-DAQmx and the NI 6624, you can consult the
following documents:
NI 6624 Calibration Procedure
•
NI-DAQmx Help—This help file contains general information about
measurement concepts, key NI-DAQmx concepts, and common
applications that apply to all programming environments.
•
NI-DAQmx C Reference Help—This help file contains C reference and
general information about measurement concepts.
•
DAQ Getting Started guides—These guides describe how to install
NI-DAQmx for Windows software and NI-DAQmx-supported DAQ
devices, and how to confirm that your device is operating properly.
2
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•
NI 6624 User Manual—This document describes the electrical and
mechanical aspects of the NI 6624 and contains information about its
operation and programming.
•
NI 6624 Specifications—This document lists the specifications for the
NI 6624. The limits you use to verify the accuracy of the device are based
on the specifications found in this document. You can download the latest
version of this document from the NI Web site at ni.com/manuals.
These documents are installed with NI-DAQmx. You can also find the latest
versions of the documentation at ni.com/manuals.
Calibration Interval
NI recommends that you perform a complete calibration at least once every
year. You can shorten this interval based on the accuracy requirements of
your application.
Test Equipment
NI recommends that you use the equipment in Table 1 for calibrating the
NI 6624.
Table 1. Recommended Equipment
Recommended
Model
Equipment
PXI-6608
≤1 ppm uncertainty for
measurement
+5 V Power
Source
—
Must be able to source
current of at least 1 A.
Discrete Resistors
—
5% precision
Resistor values: 500 Ω (× 2)
External Counter
Note
Minimum Requirements
Cable
SH100-100-F
—
Connector Block
SCB-100
—
You also need a CompactPCI-to-PCI adapter if you are calibrating the PXI-6624.
© National Instruments Corporation
3
NI 6624 Calibration Procedure
Test Conditions
Follow these guidelines to optimize the equipment and the environment
during calibration:
NI 6624 Calibration Procedure
•
Keep connections to the device as short as possible. Long cables and
wires act as antennae, picking up extra noise that can affect
measurements.
•
Verify that all connections to the device, including front panel
connections, are secure.
•
Maintain an ambient temperature of 25 °C. The device temperature
will be greater than the ambient temperature.
•
Keep relative humidity below 80%.
•
Allow a warm up time of at least 15 minutes to ensure that the
measurement circuitry is at a stable operating temperature.
•
Use shielded copper wire for all cable connections to the device. Use
twisted-pairs wire to eliminate noise and thermal offsets.
•
Ensure that the PXI chassis fan speed is set to HIGH, that the fan filters
are clean, and that the empty slots contain filler panels. For more
information, refer to the Maintain Forced-Air Cooling Note to Users
document available at ni.com/manuals.
•
Plug the chassis and the instrument into the same power strip to avoid
ground loops.
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ni.com
Device Pinout
Figure 1 shows the pinout of the NI 6624.
PFI 39 +/CTR 0 SOURCE +
1
51
PFI 23 +/CTR 4 SOURCE +
PFI 39 – /CTR 0 SOURCE –
2
52
PFI 23 – /CTR 4 SOURCE –
PFI 38 +/CTR 0 GATE +
3
53
PFI 22 +/CTR 4 GATE +
PFI 38 – /CTR 0 GATE –
4
54
PFI 22 – /CTR 4 GATE –
PFI 37 +/CTR 0 AUX+
5
55
PFI 21 +/CTR 4 AUX +
PFI 37 – /CTR 0 AUX–
6
56
PFI 21 – /CTR 4 AUX –
PFI 36 Vdd/CTR 0 Vdd
7
57
PFI 20 Vdd/CTR 4 Vdd
PFI 36 Vss/CTR 0 Vss
8
58
PFI 20 Vss/CTR 4 Vss
PFI 36/CTR 0 OUT
9
59
PFI 20/CTR 4 OUT
PFI 36 Vss/CTR 0 Vss
10 60
PFI 20 Vss/CTR 4 Vss
PFI 35 +/CTR 1 SOURCE +
11 61
PFI 19 +/CTR 5 SOURCE +
PFI 35 – /CTR 1 SOURCE –
12 62
PFI 19 – /CTR 5 SOURCE –
PFI 34 +/CTR 1 GATE +
13 63
PFI 18 +/CTR 5 GATE +
PFI 34 – /CTR 1 GATE –
14 64
PFI 18 –/CTR 5 GATE –
PFI 33 +/CTR 1 AUX +
15 65
PFI 17 +/CTR 5 AUX +
PFI 33 – /CTR 1 AUX –
16 66
PFI 17 – /CTR 5 AUX –
PFI 32 Vdd/CTR 1 Vdd
17 67
PFI 16 Vdd/CTR 5 Vdd
PFI 32 Vss/CTR 1 Vss
18 68
PFI 16 Vss/CTR 5 Vss
PFI 32/CTR 1 OUT
19 69
PFI 16/CTR 5 OUT
PFI 32 Vss/CTR 1 Vss
20 70
PFI 16 Vss/CTR 5 Vss
PFI 31 +/CTR 2 SOURCE +
21 71
PFI 15 +/CTR 6 SOURCE +
PFI 31 – /CTR 2 SOURCE –
22 72
PFI 15 –/CTR 6 SOURCE –
PFI 30 +/CTR 2 GATE +
23 73
PFI 14 +/CTR 6 GATE +
PFI 30 – /CTR 2 GATE –
24 74
PFI 14 – /CTR 6 GATE –
PFI 29 +/CTR 2 AUX +
25 75
PFI 13 +/CTR 6 AUX +
PFI 29 – /CTR 2 AUX –
26 76
PFI 13 – /CTR 6 AUX –
PFI 28 Vdd/CTR 2 Vdd
27 77
PFI 12 Vdd/CTR 6 Vdd
PFI 28 Vss/CTR 2 Vss
28 78
PFI 12 Vss/CTR 6 Vss
PFI 28/CTR 2 OUT
29 79
PFI 12/CTR 6 OUT
PFI 28 Vss/CTR 2 Vss
30 80
PFI 12 Vss/CTR 6 Vss
PFI 27 +/CTR 3 SOURCE +
31 81
PFI 11 +/CTR 7 SOURCE +
PFI 27 – /CTR 3 SOURCE –
32 82
PFI 11 – /CTR 7 SOURCE –
PFI 26 +/CTR 3 GATE +
33 83
PFI 10 +/CTR 7 GATE +
PFI 26 – /CTR 3 GATE –
34 84
PFI 10 – /CTR 7 GATE –
PFI 25 +/CTR 3 AUX +
35 85
PFI 9 +/CTR 7 AUX +
PFI 25 –/CTR 3 AUX –
36 86
PFI 9 – /CTR 7 AUX –
PFI 24 Vdd/CTR 3 Vdd
37 87
PFI 8 Vdd/CTR 7 Vdd
PFI 24 Vss/CTR 3 Vss
38 88
PFI 8 Vss/CTR 7 Vss
PFI 24/CTR 3 OUT
39 89
PFI 8/CTR 7 OUT
PFI 24 Vss/CTR 3 Vss
40 90
PFI 8 Vss/CTR 7 Vss
PFI 0 +
41 91
PFI 4 +
PFI 0 –
42 92
PFI 4 –
NC
43 93
NC
NC
44 94
NC
NC
45 95
NC
NC
46 96
NC
NC
47 97
NC
NC
48 98
NC
NC
49 99
NC
NC
50 100
NC
NC = No Connect
Figure 1. NI 6624 Pinout
© National Instruments Corporation
5
NI 6624 Calibration Procedure
Calibration Process
When calibrating the NI 6624, you first use the 20 MHz timebase on the
NI 6624 as the source to generate a 1 Hz square wave signal. The external
counter measures the frequency of the square wave signal. You then calculate
the frequency of the crystal oscillator to determine if the NI 6624 is operating
within its specifications. Figure 2 illustrates the calibration process.
20 MHz Timebase
1s
CTR 0 on the NI 6624
External Counter
Source
Output
Counter Input
Figure 2. NI 6624 Calibration Process
The frequency measurement has an uncertainty that is equal to the sum of
the propagation delay of the NI 6624 and the error of the external counter.
The maximum propagation delay is 500 ns. Using a measurement duration
of 1 s, the propagation delay uncertainty can be calculated as follows:
500 ns
--------------- = 0.5 ppm
1s
The error of the external counter must be 1 ppm or less, as specified in the
Test Equipment section of this document. The measurement uncertainty
equals the sum of 0.5 ppm and 1 ppm, that is, 1.5 ppm. Therefore, the
calculated frequency allows for a 1.5 ppm measurement uncertainty. You
can reduce measurement uncertainty by using a more stable external
counter, by increasing the measurement duration, or both.
The calibration process includes the following steps:
NI 6624 Calibration Procedure
1.
Initial Setup—Set up the test equipment for calibration.
2.
Verification—Verify the existing operation of the device. This step
confirms whether the device is operating within its specifications.
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Initial Setup
Refer to the DAQ Getting Started guides for information about how to
install the software and hardware and how to configure the device in
Measurement & Automation Explorer (MAX). NI recommends that you
use the PXI-6608 to provide the external counter. You can use an
alternative counter if it meets the requirements described in the Test
Equipment section of this document.
If you are calibrating the PXI-6624 on a PXI chassis, the measured frequency is that
of the PXI backplane clock instead of the onboard crystal oscillator. To verify the onboard
crystal oscillator, you must calibrate the PXI-6624 on a PCI chassis using a
CompactPCI-to-PCI adapter.
Note
Complete the following steps to set up the test equipment for calibration:
1.
Cable the NI 6624 to a 100-pin connector block.
2.
Wire the +5 V power source to the connector block. Refer to Figure 3
for the calibration connections.
a.
Wire the +5 V power terminal to the connector block terminal that
is connected to the PFI 36 Vdd/CTR 0 Vdd pin (pin 7) on the
NI 6624.
b.
Wire the ground of the +5 V power source to the connector block
terminal that is connected to the PFI 36 Vss/CTR 0 Vss pin (pin 8)
on the NI 6624.
PFI 36 Vdd/CTR 0 Vdd
(Pin 7)
500 Ω
500 Ω
–
PFI 36/CTR 0 OUT
(Pin 9)
PFI 36 Vss/CTR 0 Vss
(Pin 8)
+
+5 V
Power
External
Counter
Connector Block
NI 6624
Figure 3. Calibration Connections
© National Instruments Corporation
7
NI 6624 Calibration Procedure
3.
Wire a 500 Ω resistor between the connector block terminals that are
connected to the PFI 36 Vdd/CTR 0 Vdd pin (pin 7) and PFI 36/CTR
0 OUT pin (pin 9) on the NI 6624. Wire another 500 Ω resistor to the
connector block terminal that is connected to the PFI 36/CTR 0 OUT
pin (pin 9) on the NI 6624, as Figure 3 shows.
4.
Connect the external counter to the connector block using twisted-pair
wires.
a.
Wire the input of the external counter to the other end of the 500 Ω
resistor that is connected to the PFI 36/CTR 0 OUT pin (pin 9) on
the NI 6624.
b.
Wire the ground of the external counter to the connector block
terminal that is connected to the PFI 36 Vss/CTR 0 Vss pin (pin 8)
on the NI 6624.
Verification
Complete the following steps to verify the operation of the crystal oscillator
on the NI 6624:
1.
Configure counter 0 on the NI 6624 to generate a 1 Hz continuous
square wave signal with a 50% duty cycle on the PFI 36/CTR 0 OUT
pin (pin 9).
2.
Measure the frequency of the generated signal using the external
counter. It might take some time for the external counter to measure the
1 Hz signal.
3.
Multiply the measured frequency with 20,000,000 to calculate the
number of pulses that should occur in one second.
4.
Compare the frequency value you calculated from the measurement
result with the following values:
a.
If the frequency you measured falls between the upper limit of
20,001,000 Hz and the lower limit of 19,999,000 Hz, your device
is operating within its specifications.
b.
If the frequency you measured is above 20,001,000 Hz or below
19,999,000 Hz, your device is nonfunctional. Return the device to
NI for repair or replacement.
Limits in this document are based upon the December 2006 edition of the NI 6624
Specifications. Refer to the most recent NI 6624 specifications online at ni.com/manuals.
If a more recent edition of the specifications is available, recalculate the limits based upon the
latest specifications.
Note
NI 6624 Calibration Procedure
8
ni.com
Where to Go for Support
The National Instruments Web site is your complete resource for technical
support. At ni.com/support you have access to everything from
troubleshooting and application development self-help resources to email
and phone assistance from NI Application Engineers.
National Instruments corporate headquarters is located at
11500 North Mopac Expressway, Austin, Texas, 78759-3504.
National Instruments also has offices located around the world to help
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