PXI-2521 Overview

PXI-2521 Pinout


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Table 1. Signal Descriptions
Signal Description
CHx+ Positive signal connection
CHx- Negative signal connection
COMx+ Routing destination for the corresponding positive signal connection
COMx- Routing destination for the corresponding negative signal connection

PXI-2521 Hardware Diagram

This figure shows the hardware diagram of the module.


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Refer to the following list for relay names on the module.

k0...k39

PXI-2521 Topology

Module software name: 2521/40-DPST (NISWITCH_TOPOLOGY_2521_40_DPST)

The module is composed of 40 armature non-latching DPST relays.

For certain applications, you may need to increase the default settling time.

Note Switching inductive loads (for example, motors and solenoids) can produce high voltage transients in excess of the module's rated voltage. Without additional protection, these transients can interfere with module operation and impact relay life.

40-DPST Topology


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Making a Connection

You can control the channels using the niSwitch Connect Channels VI or the niSwitch_Connect function.

For example, to close the relay of channel 2, call niSwitch_Connect(vi, "ch2", "com2"). To open the relay of channel 2, call niSwitch_Disconnect(vi, "ch2", "com2").

When scanning the module, a typical scan list entry could be ch2->com2;. This entry closes the relay between CH2 and COM2.

PXI-2521 Relay Replacement

The module uses electromechanical armature relays.

Note The module uses a custom lead length to meet safety standards. Trim leads to no more than 1 mm (0.04 in.) from the PCB. You also can use the spare relay included with the module at location K40.

Refer to the following table for information about ordering replacement relays.

Replacement Relay Part Number
Tyco Electronics (relay manufacturer) 1462043-6
NI relay kit (10 relays) 782461-10

Ensure you have the following:

  • Temperature-regulated soldering iron set to 371 °C (700 °F) for lead-free solder rework
  • 96.5/3.0/0.5 Tin/Silver/Copper solder (flux core) for lead-free solder rework
  • Solder wick
  • Fine pick
  • Isopropyl alcohol
  • Cotton swabs
Note The module uses lead-free assemblies. NI recommends using lead-free solder for relay replacement on lead-free assemblies.
Notice Do not rework lead assemblies using a lead-free work station. Lead solder from the unit could contaminate the station.
Notice If a lead-free assembly is reworked with lead solder, label the assembly to indicate this. This can prevent the same unit from being reworked later on a lead-free solder station, which could contaminate the station.

Complete the following steps to disassemble your module and replace a failed relay.

  1. Ground yourself using a grounding strap or a ground connected to your PXI chassis.
    Note Properly grounding yourself prevents damage to your module from electrostatic discharge.
  2. Locate the relay you want to replace. Relay names are labeled on the front of the module. The following table maps the relay names to the channel names.
    Channel NameRelay NameChannel NameRelay Name
    ch0 K0 ch20 K20
    ch1K1ch21K21
    ch2K2ch22K22
    ch3K3ch23K23
    ch4K4ch24K24
    ch5K5ch25K25
    ch6K6ch26K26
    ch7K7ch27K27
    ch8K8ch28K28
    ch9K9ch29K29
    ch10K10ch30K30
    ch11K11ch31K31
    ch12K12ch32K32
    ch13K13ch33K33
    ch14K14ch34K34
    ch15K15ch35K35
    ch16K16ch36K36
    ch17K17ch37K37
    ch18K18ch38K38
    ch19K19ch39K39
  3. Replace the relay as you would any other through-hole part. Trim the replaced relay leads to no more than 1 mm (0.04 in.) from the PCB.
Tip Use the NI-SWITCH Switch Soft Front Panel to reset the relay count after you have replaced a failed relay. Refer to the Switch Soft Front Panel Help for more information.