OPERATING INSTRUCTIONS
FP-RLY-420
8-Channel, SPST Relay Module
These operating instructions describe the installation, features, and
characteristics of the FP-RLY-420. For details on configuring and
accessing the FP-RL Y-420 o ver a network, refer to the user manual
for the particular FieldPoint network module you are using with
the FP-RLY-420.
Features
The FP-RLY-420 is a FieldPoint relay output module with the
following features:
• Eight Single-Pole Single-Throw (SPST) 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
Power Requirement
The FP-RLY-420 is powered via the local backplane bus from the
FieldPoint network module. The FP-RLY-420 is a high-power
consumption module and requires more than the nominal power
allocated to an I/O module from the network module. In some
applications, this could limit the number of I/O modules that you
can connect to a single network module.
When defining a FieldPoint system that uses an FP-RLY-420
module, you must calculate the power consumption. First refer
to the specifications section in the user manual for your network
FieldPoint ™ is a trademark of National Instruments Corporation. Product and company names
mentioned herein are trademarks or trade names of their respective companies.
321904B-01 © Copyright 1998, 1999 National Instruments Corp. All rights reserved. June 1999
module. The maximum number of terminal bases per bank
multiplied by 1 watt is the total power the network module can
supply. For example, an FP-1000 or FP-1001 can support nine
terminal bases (9*1 W = 9 W).
Next, refer to the specifications section in the operating
instructions for the I/O modules. Use the Power from Network
Module specification. For example, a bank of modules consisting
of four FP-RL Y-420 and fi ve FP-DI-301 modules requires a total of
8.4 W from the FieldPoint network module [4*(1.7 W) + 5*(0.325
W) = 8.4 W]. This power requirement is less than the 9 W
maximum and is therefore acceptable.
Installation
The FP-RLY-420 mounts on a FieldPoint terminal base
(FP-TB-xx) unit. The hot plug and play operation of the
FP-RLY-420 allows you to install it onto a powered terminal base
without disturbing the operation of other modules or terminal
bases. The FP-RLY-420 receives operating power from the
terminal base.
T o install the FP-RLY-420, 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-420 module).
2. Align the FP-RLY-420 alignment slots with the guide rails on
the terminal base.
3. Press firmly to seat the FP-RLY-420 on the terminal base. The
terminal base latch locks the FP-RLY-420 into place when it is
firmly seated.
Key
Latch
Alignment
Slot
Guide Rails
Terminal BaseI/O Module
Figure 1.
FP-RLY-420 2 www.natinst.com
Module Installation Diagram
Field Wiring
The terminal base has connections for each of the eight relay
channels and an external supply to po wer f ield de vices. Each relay
channel of the FP-RLY-420 has two terminals: N.O. (Normally
Open) and I.C. (Isolated Common). The external supply is not
needed for the internal operation of the FP-RLY-420; 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 6 A.
Table 1 lists the terminal assignments for the signals of each
channel.
Table 1.
Chan-
nel
0 1 2 17 18
1 3 4 19 20
2 5 6 21 22
3 7 8 23 24
4 9 10 25 26
5 11 12 27 28
6 13 14 29 30
7 15 16 31 32
N.O. I.C.
Terminal Assignments
Terminal Numbers
V
sup
COM
© National Instruments Corp. 3 FP-RLY-420
Figures 2a and 2b show examples of basic wiring connections.
+
VC
a. Total Current Less
Than 6 Amps
V
N.O.
I.C.
COM
V
N.O.
I.C.
COM
sup
sup
Load
Load
–
N.O.
Load
I.C.
N.O.
I.C.
Load
b. Total Current Greater
Than 6 Amps
+
–
+
–
Figure 2. Basic Field Connection (Two Channels Shown)
Relay Output Circuit
The outputs of the FP-RLY-420 consist of Form A
electromechanical relays. The power-up state is of f (open) to
ensure safe installation. In the ON state, the N.O. and I.C. contacts
connect together to form a short circuit. Choose the impedance of
the loads so that the current switched b y any one channel in t he ON
state is no more than 3 A.
In the ON state, there is an effectiv e resistance of 100 mΩ between
the N.O. and I.C. terminals, which causes a voltage drop. For
example, if the current is 3 A, the voltage drop across the N.O.
and I.C. terminals is 0.3 V.
FP-RLY-420 4 www.natinst.com
Figure 3 shows the diagram of one channel’s relay output circuit.
V
V
sup
N.O.
I.C.
COM
C
Figure 3.
Relay Output Circuit
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.
3
2.5
Current
(Amps)
2
1.5
1
.5
Safe Operating
Region
2004060
Figure 4.
Maximum Current vs. DC Volts
DC Volts
80 100 120
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.
© National Instruments Corp. 5 FP-RLY-420
In addition, the FP-RLY-420 contains its own internal protection
MOV to prevent excessively high voltage from being applied
across the contacts. The MOV is located between the N.O. and I.C.
contacts of each relay, but National Instruments still recommends
the use of a protection circuit across your inductive load.
Guidelines for Selecting Contact Protection Circuits
Proper selection is critical as the use of 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.
T ypically you should mount a protectiv e device within 18 in. of the
load or contact.
T ypically , contact-protection circuits are provided for an ov erview,
but you should thoroughly examine the circuit you are plann ing to
use. For more specific information on any of these circuits, contact
the Technical Services Department at American Zettler, Inc.
Diode and Zener Diode Circuit
Diagram Notes
1
Use in DC applications only.
Use when diode circuit causes too long
release time.
Load
Use zener diode with zener voltage about
equal to power supply voltage.
1
This section has been reprinted with permission from American Zettler, Inc.
FP-RLY-420 6 www.natinst.com
Diode Circuit
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.
Load
For smaller voltages, use reverse breakdown
voltage of 2 to 3 times power supply voltage.
CR Circuits
Diagram Notes
Load
Load
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.
Varistor Circuit
Diagram Notes
Effective for A C and DC
applications.
Circuit slightly delays release time.
Load
Effective when connected to both
contacts, power supply voltage
across the load is 100 to 200 V.
© National Instruments Corp. 7 FP-RLY-420
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 follo wing
chart.
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
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
current
Status Indicators
Figure 5 shows the module label and status indicators. You can
remove the insertable label to see wiring diagrams for the input
channels.
Figure 5.
FP-RLY-420 8 www.natinst.com
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-420 informs the network module of its presence. When
the network module recognizes the FP-RLY-420, the network
module sends initial configuration information to the FP-RLY -42 0.
After receiving this initial information, the green READY
indicator lights and the FP-RLY-420 is in its normal operating
mode. In addition to the green POWER and READY indicators,
each channel has a numbered, green, output state indicator that
lights when the channel is in the ON state.
Isolation and Safety Guidelines
Caution
attempting to connect ANY circuits that may contain
hazardous voltages to the FP-RLY-420.
This section describes the isolation of the FP-RLY-420 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 up to
3000 Vrms. In addition, the FP-RLY-420 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-420 is) for such an
application.
Even when a product like the FP-RLY-420 is used in applications
with hazardous potentials, follow these guidelines to ensure a safe
total system:
• The safe ty isolation of the FP-RLY-420 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.
Read the following information before
© National Instruments Corp. 9 FP-RLY-420
•Do not 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.
• 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-420 is certified as double
insulated for normal operating voltages of 250 Vrms. Do not
use the FP-RLY-420 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..........................8
Relay type.........................................1 Form A (SPST)
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
Note
Above 55 °C ambient, max. 1.5 A per channel.
Minimum switching voltage.............10 mA at 5 VDC
On resistance.....................................100 mΩ
Off state leakage ...............................0.3 µA at 250 VAC
Expected Life
Mechanical .................................20 × 106 operations min.
Electrical (at 30 cpm)................. 300,000 operations at 3 A,
35 VDC
100,000 operations at 3 A,
250 VAC
FP-RLY-420 10 www.natinst.com
Maximum switching frequency
Mechanical .................................20 operations per second
Electrical.....................................1 operation per second at
maximum load
Relays operate time...........................6 ms typical, 8 ms max.
Relays release time ...........................3 ms typical, 4 ms max.
Relay bounce time ............................3 ms max.
Contact material................................ Gold-plated silver cadmium
oxide
Isolation (CH–GND and CH–CH)....3,000 Vrms
Safety isolation, working voltage
(CH–GND only) ...............................250 Vrms, designed per IEC
1010 as double insulated
Physical
Indicators ..........................................Green POWER and
Weight...............................................160 g (5.6 oz.)
READY indicators, 8 green
output state indicators
Power Requirements
Power from network module............1700 mW
Environment
Operating temperature......................–40 to +70 °C
Storage temperature..........................–55 to +100 °C
Relative humidity..............................5% to 90% noncondensing
CE Mark Compliance
This product meets applicable EU directive(s) as follows:
Safety isolation .................................EN 61010 (double insulation
EMC Directive
Immunity.................................... EN 50082-1:1994
Emissions ...................................EN 55011:1991 Group I
© National Instruments Corp. 11 FP-RLY-420
for 250 Vrms working
isolation, installation
category II)
Class A at 10 m
Mechanical Dimensions
Figure 6 shows the mechanical dimensions of the FP-RLY-420
installed onto a terminal base. Dimensions are given in inches
[millimeters].
4.22 [107.19]
4.31
[109.5]
3.60 [91.44]
Figure 6.
Mechanical Dimensions
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