multifunction-rio-user-manual.pdf - 第46页

Chapter 2 Hardware Overv iew of the NI 78x x Multifunction Reconfigurable I/O U ser Manual 2-28 ni.com 3. Replace the blo wn fuse while referring to Figure 2-18 for the fuse locations. Figure 2-18. NI 784 x /785 x Replac…

Chapter 2 Hardware Overview of the NI 78xx

Older revision NI 781x/783x devices have a self-resetting fuse to protect

the supply from overcurrent conditions. This fuse resets automatically

within a few seconds after the overcurrent condition is removed. For more

information about the self-resetting fuse and precautions to take to

avoid improper connection of +5 V and ground terminals, refer to the

KnowledgeBase document, Self-Resetting Fuse Additional Information,

by going to

ni.com/info and entering the info code pptc.

(NI 784x /785x Devices) All NI 784x/785x devices have a user-replaceable

socketed fuse to protect the supply from overcurrent conditions. When an

overcurrent condition occurs, check your cabling to the +5 V terminals and

replace the fuse as described in the Device Fuse Replacement (NI

784x/785x Only) section.

Caution Never connect the +5 V power terminals to analog or digital ground or to any

other voltage source on the NI 78xx device or any other device. Doing so can damage the

device and the computer. NI is not liable for damage resulting from such a connection.

The power rating on most devices is +4.75 to +5.25 VDC at 1 A.

Refer to the Multifunction Reconfigurable I/O Specifications document,

available at

ni.com/docs, to obtain the power rating for your device.

Device Fuse Replacement (NI 784x /785x Only)

NI 784x/785x devices have a replaceable fuse, Littelfuse part

number 0453004, that protects the device from overcurrent through

the power connector.

To replace a blown fuse in the NI 784x/785x, complete the following steps:

1. Power down and unplug the computer or PXI chassis.

2. Remove the PCI/PCI Express device from the expansion slot on the

computer, or the PXI device from the PXI slot in the PXI chassis.

Chapter 2 Hardware Overview of the NI 78xx

Multifunction Reconfigurable I/O User Manual 2-28 ni.com

3. Replace the blown fuse while referring to Figure 2-18 for the fuse

locations.

Figure 2-18. NI 784x/785x Replacement Fuse Location

(Littelfuse Part Number 0453004)

4. Reinstall the PCI, PCI Express, or PXI device into the computer or PXI

chassis.

PCI Express Device Disk Drive Power Connector

(PCIe-784x/785x Devices) The disk drive power connector is a four-pin hard

drive connector on PCI Express devices that, when connected, increases the

current the device can supply on the +5 V terminal.

When to Use the Disk Drive Power Connector

PCI Express R Series devices without the disk drive power connector

installed perform identically to other R Series devices for most applications

and with most accessories. For most applications, it is not necessary to

install the disk drive power connector.

However, you should install the disk drive power connector in either of the

following situations:

• You need more power than listed in the device specifications

• You are using an R Series accessory with no external power supply,

such as the cRIO-9151

Refer to the specifications document for your device for more information

about PCI Express power requirements and power limits.

1PCIe-784x/785x Fuse Location 2PXI-784x/785x Fuse Location

Chapter 2 Hardware Overview of the NI 78xx

Disk Drive Power Connector Installation

Before installing the disk drive power connector, you must install and set

up the R Series PCI Express device as described in the Getting Started with

R Series Multifunction RIO document. Complete the following steps to

install the disk drive power connector.

1. Power off and unplug the computer.

2. Remove the computer cover.

3. Attach the PC disk drive power connector to the disk drive power

connector on the device, as shown in Figure 2-19.

Note The power available on the disk drive power connectors in a computer can vary. For

example, consider using a disk drive power connector that is not in the same power chain

as the hard drive.

Figure 2-19. Connecting to the Disk Drive Power Connector

4. Replace the computer cover, and plug in and power on the computer.

5. Use the NI 78xx Calibration Utility to run a self-calibration on the

PCIe-784x/785x device. Refer to the Self-Calibration section of

Chapter 3, Calibration (NI 783x/784x/785x Only), for more

information.

Note Connecting or disconnecting the disk drive power connector can affect the analog

performance of your device. To compensate for this, NI recommends that you

self-calibrate after connecting or disconnecting the disk drive power connector.

1 Device Disk Drive Power Connector 2 PC Disk Drive Power Connector