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USER GUIDE

NI 6520/6521

This document describes how to use the National Instruments 6520 and 
6521 data acquisition (DAQ) devices with NI-DAQ 7.5 or later. Device 
specifications can be found on 

ni.com/manuals

. If you have not already 

installed the DAQ device, refer to the 

DAQ Getting Started Guide

 for 

installation instructions.

The NI 6520/6521 contains five Form A single-pole single-throw (SPST) 
non-latching relay outputs, three Form C single-pole double-throw (SPDT) 
non-latching relay outputs, and eight channel-to-channel isolated industrial 
inputs. The relay’s maximum switching power is 60 W/60 VA. The 
maximum switching voltage for the NI 6520 is 30 Vrms/42.4 V

pk

/

60 VDC. The maximum switching voltage for the NI 6521 is 
150 VDC/VAC.

The NI 6520/6521 uses positive logic. A digital high energizes the relay, 
and a digital low deenergizes it. In the energized state, the common (COM) 
contact is connected to the normally open (NO) contact. For Form C relays 
in the deenergized state, the common contact is connected to the normally 
closed (NC) contact. For Form A relays in the deenergized state, the 
common contact is not connected to the normally open (NO) contact. When 
the board (PC) is powered off, the relays are deenergized.

Caution

(NI 6521 Only)

 This 150 V Measurement Category II module features 1,400 Vrms 

isolation between I/O channels and the backplane, as verified by a dielectric withstand test, 
5 s maximum. For more information on hazardous voltage requirements and safety 
information for the NI 6521, refer to the 

NI 6521 Isolation Voltages

 section.

Contents

Configuration .......................................................................................... 2
Functional Overview............................................................................... 3
Safety Information .................................................................................. 4
Related Documentation........................................................................... 6
Features ................................................................................................... 6

Digital Filtering................................................................................ 6

Summary of Contents for NI 6520

Page 1: ... The NI 6520 6521 uses positive logic A digital high energizes the relay and a digital low deenergizes it In the energized state the common COM contact is connected to the normally open NO contact For Form C relays in the deenergized state the common contact is connected to the normally closed NC contact For Form A relays in the deenergized state the common contact is not connected to the normally...

Page 2: ... 6520 Isolation Voltages 17 NI 6521 Isolation Voltages 18 Protecting Inductive Loads 18 Cables and Accessories 20 NI 6520 Accessory Options 20 PCI 6521 Accessory Options 21 PXI 6521 Accessory Options 21 Specifications 22 Where to Go for Support 22 Configuration The NI 6520 6521 device is completely software configurable so it is not necessary to set jumpers for I O configuration The PCI 6520 6521 ...

Page 3: ...st recent National Instruments drivers go to ni com drivers Press F5 to refresh the MAX window or close and re open MAX Reboot the computer Power off and unplug the computer or chassis and install the device in a different slot Refer to the DAQ Getting Started Guide for installation instructions and safety guidelines Functional Overview Figure 1 illustrates the key functional components of the NI ...

Page 4: ...e sure that the DIO device is completely dry and free from contaminants before returning it to service Operate the DIO device only at or below Pollution Degree 2 Pollution is foreign matter in a solid liquid or gaseous state that can reduce dielectric strength or surface resistivity The following is a description of pollution degrees Pollution Degree 1 means no pollution or only dry nonconductive ...

Page 5: ...ch as that provided by a standard wall outlet for example 115 V for U S or 230 V for Europe Examples of Measurement Category II are measurements performed on household appliances portable tools and similar DIO devices Measurement Category III is for measurements performed in the building installation at the distribution level This category refers to measurements on hard wired equipment such as equ...

Page 6: ... the DAQ Assistant Note You can download these documents from ni com manuals Features Digital Filtering Use the digital filter option available on the NI 6520 6521 input lines to eliminate glitches on input data When used with change detection filtering can also reduce the number of changes to examine and process You can configure the digital input channels to pass through a digital filter after t...

Page 7: ...t signal is recognized only if it maintains its new state for at least two consecutive rising edges of the filter clock The filter clock is programmable and allows you to control how long a pulse must last to be recognized The sample clock provides a fast sample rate to ensure that input pulses remain constant between filter clocks Digital Filtering Example Figure 2 shows a filter configuration wi...

Page 8: ...at COM and NO after power up Figure 3 Programmable Power Up States for Form C Relays The default power up state for Form A relays is deenergized control bit is low which makes the contact open at COM and NO The Form A relay status is user configurable If the power up state of a Form A relay is configured to energized control bit is high the contact connects at COM and NO after power up Figure 4 Pr...

Page 9: ...ne states The maximum rate of change detection is determined by the software response time which varies from system to system An overflow bit indicates that an additional rising or falling edge has been detected before the software could process the previous change Refer to the software documentation for information about how to set up and implement the change detection Change Detection Example Ta...

Page 10: ...og timer the outputs go to a user defined safe state and remain in that state until the watchdog timer is disarmed by the application and new values are written the NI 6520 6521 is reset or the computer is restarted The expiration signal that indicates an expired watchdog will continue to assert until the watchdog is disarmed After the watchdog timer expires the NI 6520 6521 ignores any writes unt...

Page 11: ...rmation on input connection For information on safely connecting to the NI 6521 refer to the 37 Pin High Voltage Accessory Safety Kit Installation Guide shipped with your device and also available on ni com manuals Pin Assignments Figure 5 shows the pin assignments for the 37 pin connector on the NI 6520 6521 device The naming convention for each input pin is P0 X where X is the line number and a ...

Page 12: ... 6 NC 2 0 Normally Closed These are the normally closed terminals of the relays This is the default state for the Form C relays 2 21 5 24 8 26 10 28 COM 7 0 Common These are the common terminals of the relays 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 P1 0NO P1 0COM P1 0NC P1 2NO P1 2COM P1 2NC P1 4NO P1 4COM P1 6NO P1 6COM NO CONNECT P0 0...

Page 13: ... 11 V to 4 V and 4 V to 11 V is not defined This corresponds to standard industrial 24 V logic thresholds There should never be more than a 30 V difference in P0 X and P0 X terminals Exceeding 30 V differential voltage could cause damage to the photocouplers NI 6521 Only The 30 V differential voltage can have up to 120 V common mode voltage compared to chassis digital ground of the NI 6521 device ...

Page 14: ...ge within the NI 6520 6521 device range Refer to the device specifications for information about voltage ranges Figure 6 NI 6520 Input Signal Connection Example Figure 7 NI 6521 Input Signal Connection Example P0 X P0 X 0 V 30 V or 0 V 30 V 2 43 kΩ 3 3 V AC Input Photocoupler 3 3 V P0 X P0 X Signal Common Mode 0 V 30 V or 0 V 30 V 2 43 kΩ Up to 120 V Common Mode Voltage AC Input Photocoupler ...

Page 15: ...re relays are useful in control applications when the switch must return to a known state if power is lost Figure 8 Non Latching Relay States Relay Power Ratings Caution The maximum switching current is limited by the maximum switching power the maximum voltage and must not exceed 60 W 60 VA NI PCI 6520 Only The maximum power rating for the NI PCI 6520 relays is 60 W or 60 VA with a maximum curren...

Page 16: ...relays on the NI 6520 6521 have the default statuses of deenergized control bit is low in both power on and power off states For more information on default states of the NI 6520 6521 relays refer to the Programmable Power Up States section and the Non Latching Relays section Relay Signal Connection Example To connect to the NI 6520 6521 signals for Form C relays connect NC NO and COM as shown in ...

Page 17: ...e isolation on the NI 6520 6521 output channels Each relay provides isolation at one channel of output Isolation Voltages NI 6520 Isolation Voltages The terminals of each I O channel are isolated from other I O channels from the connector shell and digital ground Isolation barriers provide isolation up to 30 Vrms 42 4 Vpk 60 VDC between any two terminals except between the two terminals making up ...

Page 18: ...ct The NI 6521 must be used with special keyed cables and accessories Refer to the 37 Pin High Voltage Accessory Safety Kit Installation Guide shipped with your device and the NI 6520 Accessory Options section for more information The PCI 6521 must be installed in a PC that adequately grounds the front panel bracket to the chassis of the PC Do not remove covers from the NI PCI 6521 Doing so can re...

Page 19: ...ults mount the flyback diode within 18 inches of the load Figure 12 shows an external flyback diode installed across an inductive load for DC loads Figure 13 shows a MOV installed across an inductive load for AC loads Figure 12 Contact Protection for DC Inductive Loads Figure 13 Contact Protection for AC Inductive Loads VDC GND CHAN NI 6520 6521 V Flyback Diode MOV Inductive Load VAC GND CHAN NI 6...

Page 20: ...part number 778621 01 1 m and 778621 02 2 m SH37F P 4 37 Pin Female to Pigtails Shielded I O Cable part number 778620 04 4 m R37F 37M 1 37 Pin Female to Male Ribbon I O Cable part number 779195 01 1 m Or choose from the following custom connectivity options SH37F P 4 37 Pin Female to Pigtails Shielded I O Cable part number 778620 04 4 m TB 37F 37CP 37 Pin Crimp Poke Terminals Shell with Strain Rel...

Page 21: ... 37 Pin Crimp Poke Terminals Shell with Strain Relief part number 779185 01 PXI 6521 Accessory Options Caution The NI 6521 must be used with special keyed cables and accessories Refer to the 37 Pin High Voltage Accessory Safety Kit Installation Guide shipped with your device for more information about keying for safety 37 Pin High Voltage Accessory Safety Kit part number 779445 01 And your choice ...

Page 22: ...e DoC for your product by visiting ni com certification If your product supports calibration you can obtain the calibration certificate for your product at ni com calibration 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 address your support needs For telephone su...

Page 23: ...ames of their respective companies For patents covering National Instruments products refer to the appropriate location Help Patents in your software the patents txt file on your CD or ni com patents 2007 National Instruments Corporation All rights reserved 372280A 01 Aprl07 South Africa 27 0 11 805 8197 Spain 34 91 640 0085 Sweden 46 0 8 587 895 00 Switzerland 41 56 2005151 Taiwan 886 02 2377 222...

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