National Instruments FP-RLY-422 User manual

FieldPoint ™is a trademark of National Instruments Corporation. Product and company names
mentioned herein are trademarks or trade names of their respective companies.
322450A-01 ©Copyright 1999 National Instruments Corp. All rights reserved. September 1999
OPERATING INSTRUCTIONS
FP-RLY-422
4-Channel, SPDT Relay Module
These operating instructions describe the installation, features, and
characteristics of the FP-RLY-422. For details on configuring and
accessing the FP-RLY-422 over a network, refer to the user manual
for the particular FieldPoint network module you are using with
the FP-RLY-422.
Features
The FP-RLY-422 is a FieldPoint relay output module with the
following features:
• Four Single-Pole Double-Throw (SPDT) relay channels
• Switching capacity 3 A at 35 VDC or 250 VAC
• On/Off LED indicators
• Hot plug and play operation
• 3,000 V input to output isolation
• Double insulated for 250 V safe working voltage
• –40 to +70 °C operation
Installation
The FP-RLY-422 mounts on a FieldPoint terminal base
(FP-TB-xx) unit. The hot plug and play operation of the
FP-RLY-422 allows you to install it onto a powered terminal base
without disturbing the operation of other modules or terminal
bases. The FP-RLY-422 receives operating power from the
terminal base.

FP-RLY-422 2 www.natinst.com
To install the FP-RLY-422, refer to Figure 1 and follow these steps:
1. Slide the terminal base key to either position X (used for any
module) or position 7 (used for the FP-RLY-422 module).
2. Align the FP-RLY-422 alignment slots with the guide rails on
the terminal base.
3. Press firmly to seat the FP-RLY-422 on the terminal base. The
terminal base latch locks the FP-RLY-422 into place when it is
firmly seated.
Figure 1. Module Installation Diagram
Field Wiring
The terminal base has connections for each of the four relay
channels and an external supply to power field devices. Each relay
channel of the FP-RLY-422 has four terminals: one N.Open
(Normally Open), two I.Com (Isolated Common), and one
N.Closed(NormallyClosed). The external supply is not needed for
the internal operation of the FP-RLY-422; however, you may
connect an external supply to power field devices by connecting to
the V and C terminals of the terminal base. If you connect an
external supply to the V and C terminals, the total current supplied
cannot exceed 5 A.
Alignment
Slot
Key
Latch
Guide Rails
Terminal BaseI/O Module

© National Instruments Corp. 3 FP-RLY-422
Table 1 lists the terminal assignments for the signals of each
channel.
Figures 2a and 2b show examples of basic wiring connections.
Figure 2. Basic Field Connection
Table 1. Terminal Assignments
Channel
Terminal Numbers
N.Open I.Com N.Closed VSUP COM
0 1 2,3 417 18
19 20
1 5 6,7 821 22
23 24
2 9 10,11 12 25 26
27 28
313 14,15 16 29 30
31 32
a. Total Current Less
Than 5 Amps b. Total Current Greater Than 5 Amps
VC Vsup
–
+
N.Open
I.Com
I.Com
Vsup
N.Closed
COM
Load
Load
N.Closed
I.Com
N.Open
I.Com
–
+
Load
Load

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Relay Output Circuit
The outputs of the FP-RLY-422 consist of four independent
Form C electromechanical relays. The relays are
break-before-make, but only if you do not exceed the specified
relay operation speed. All relays remain in their power-up state or
OFF state (N.Closed connected to I.Com) until the relay (Channel)
is turned on. This will break the N.Closed–I.Com connection and
connect I.Com to N.Open. Choose the impedance of the loads so
that the current switched by any one channel is no more than 3 A.
Each relay can be controlled separately without affecting the
others, or all relays can change states at the same time.
There is an effective resistance of 100 mΩbetween I.Com and
N.Closed or N.Open. This resistance will cause a voltage drop. For
example, if the current is 3 A, the voltage drop across the I.Com
and N.Closed or N.Open terminals is 0.3 V.
Figure 3 shows the diagram of one channel’s relay output circuit.
Figure 3. Relay Output Circuit
N.Open
I.Com
COM
C
V
Vsup
I.Com
N.Closed

© National Instruments Corp. 5 FP-RLY-422
The maximum switching capacity of each relay is 3 A up to
250 VAC or 35 VDC. To switch greater DC voltages, refer to
Figure 4.
Figure 4. Maximum Current vs. DC Volts
Contact Protection for Inductive Loads
When inductive loads are connected to the relays, a large
counter-electromotive force may occur at relay switching time
because of the energy stored in the inductive load. These flyback
voltages can severely damage the relay contacts and greatly
shorten the life of the relay.
It is best to limit these flyback voltages at your inductive load by
installing, across your inductive load, a flyback diode for DC loads
or a metal oxide varistor (MOV) for AC loads. Refer to the next
section, Guidelines for Selecting Contact Protection Circuits, for
more information.
In addition, the FP-RLY-422 contains its own internal protection
MOV to prevent excessively high voltage from being applied
across the contacts. Each channel contains two MOVs: one
betweenN.Closed and I.Com andonebetweenN.OpenandI.Com.
However, National Instruments still recommends the use of a
protection circuit across your inductive load.
2004060
DC Volts
Current
(Amps)
80 100 120
.5
1
1.5
2
2.5
3
Safe Operating
Region

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Guidelines for Selecting Contact
Protection Circuits1
Proper selection is critical as the useof a contact-protection device
can extend contact life. When mounting the protection device,
always locate it near the immediate area of the load or contact.
Typically you should mount a protective device within 18 in. of the
load or contact.
Typically, contact-protection circuits are provided foran overview,
but you should thoroughly examine the circuit you are planning
to use.
Diode and Zener Diode Circuit
Diode Circuit
1 This section has been reprinted with permission from American Zettler, Inc.
Diagram Notes
Use in DC applications only.
Use when diode circuit causes too long
release time.
Use zener diode with zener voltage about
equal to power supply voltage.
Diagram Notes
Use in DC applications only.
Compared to RC type, circuit delays release
time (2 to 5 times values stated in catalog).
For larger voltages, use diode with reverse
breakdown 10 times circuit voltage and
forward load circuit.
For smaller voltages, use reverse breakdown
voltage of 2 to 3 times power supply voltage.
Load
Load

© National Instruments Corp. 7 FP-RLY-422
CR Circuits
Varistor Circuit
In-Rush Current
The type of load and its in-rush current characteristics, together
with switching frequency, can cause contact welding. For loads
with in-rush current, measure the steady state current and in-rush
current to determine the proper relay. Some typical types of loads
and the in-rush current they create are summarized in the following
table.
Diagram Notes
Circuit A is suitable for AC or DC
applications, but if used with AC
voltage, impedance of the load
should be smaller than the CR
circuit’s. Do not utilize for timer
loads, as leakage current can cause
faulty operations.
Circuit B is suitable for AC or DC.
If the load is a relay or solenoid,
release times lengthen. Effective
when connected to both contacts,
power supply voltage across the
load is 100 to 200 V.
Diagram Notes
Effective for AC and DC
applications.
Circuitslightlydelaysreleasetime.
Effective when connected to both
contacts, power supply voltage
across the load is 100 to 200 V.
Load
Load
Load

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Status Indicators
Figure 5 shows the module label and status indicators. You can
remove the insertable label to see wiring diagrams for the relay
channels.
Figure 5. Status Indicators and Module Label
After the module has been inserted into a terminal base (and
power is applied), the green POWER indicator lights and the
FP-RLY-422 informs the network module of its presence. When
the network module recognizes the FP-RLY-422, the network
module sends initial configuration information to the FP-RLY-422.
After receiving this initial information, the green READY
indicator lights and the FP-RLY-422 is in its normal operating
mode. In addition to the green POWER and READY indicators,
each channel has two, green, output state indicators labeled
Table 2. Typical Load Types and In-Rush Currents
Type of Load In-Rush Current
Resistive load Steady-state current
Solenoid load 10 to 20 times the steady-state current
Motor load 5 to 10 times the steady-state current
Incandescent lamp load 10 to 15 times the steady-state current
Mercury lamp load Approximately 3 times the steady-state
current
Sodium vapor lamp load 1 to 3 times the steady-state current
Capacitive load 20 to 40 times the steady-state current
Transformer load 5 to 15 times the steady-state current
4-Ch. SPDT Relay
0123
NO NC NO NC NO NC NO NC

© National Instruments Corp. 9 FP-RLY-422
NO and NC. The indicators show which terminal is connected
to I.Com.
Isolation and Safety Guidelines
Caution Read the following information before
attempting to connect ANY circuits that may contain
hazardous voltages to the FP-RLY-422.
This section describes the isolation of the FP-RLY-422 and its
compliance with international safety standards. The outputs are
isolated from the backplane of the terminal base with an isolation
barrier designed and tested to protect against fault voltages of upto
3000 Vrms. In addition, the FP-RLY-422 provides double
insulation (compliant to UL and IEC safety standards) for
working common-mode voltages of 250 Vrms. Safety standards
(such as those published by UL and IEC) require the use of double
insulation between hazardous voltages and any human-accessible
parts or circuits. You should never attempt to use any isolation
product between human-accessible parts (such as DIN rails or
monitoring stations) and circuits that may be at hazardous
potentials under normal conditions, unless the product is
specifically designed (as the FP-RLY-422 is) for such an
application.
Even when a product like the FP-RLY-422 is used in applications
with hazardous potentials, follow these guidelines to ensure a safe
total system:
• The safety isolation of the FP-RLY-422 is from input to output,
not between channels on the same module. If any of the
channels on a module are wired at a hazardous potential,
ensure that all other devices or circuits connected to that
module are properly insulated from human contact.
•Donot share the external supply voltages (V and C on the
terminal base) with other devices (including other FieldPoint
devices) unless those devices are also isolated from human
contact.

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• As with any hazardous voltage wiring, ensure that all wiring
and connections meet with applicable electrical codes or
common sense practices. Mount terminal bases in an area,
position, or cabinet that prevents accidental or unauthorized
access to wiring with hazardous voltages.
• The isolation of the FP-RLY-422 is certified as double
insulated for normal operating voltages of 250 Vrms. Do not
use the FP-RLY-422 as the sole isolating barrier between
human contact and working voltages of more than 250 Vrms.
Specifications
The following specifications are typical for the range
–40 to +70 °C, unless otherwise noted.
Input Characteristics
Number of channels..........................4
Relay type.........................................1 Form C (SPDT)
Nonlatching
Maximum Switching Capacity (Resistive Load)
AC ..............................................3 A at 250 VAC
DC ..............................................3 A at 35 VDC
2 A at 40 VDC
1 A at 55 VDC
0.4 A at 120 VDC
Minimum switching voltage.............10 mA at 5 VDC
On resistance.....................................100 mΩ
Off state leakage ...............................0.3 µA at 250 VAC
Expected Life
Mechanical .................................10 ×106operations min.
Electrical (at 30 cpm).................300,000 operations at 3 A,
35 VDC
100,000 operations at 3 A,
250 VAC
Maximum Switching Frequency
Mechanical .................................20 operations per second
Electrical.....................................1 operation per second at
maximum load
Relays operate time...........................10 ms typical, 13 ms max.
Relays release time ...........................5 ms typical, 7 ms max.