4
Publication 1794-IN049D-EN-P - January 2009
Status Indicators
When an input indicator (yellow) is lighted, it indicates that a valid signal
(active high or active low) is present at one of the Input terminals.
When wire-off detection is enabled, and a wire-off fault is detected (24 V
DC IEC 1+ input terminal only), a fault indicator (red) is blinked/flashed at
a rate of 1Hz to signal a fault condition. A wire-off fault signal will also be
sent to the backplane. A flashing red fault indication means a valid wire-off
condition for a 24 V DC IEC 1+ Input or a 24 V DC contact switch input
with a shunt resistor.
When an output indicator is yellow, the logic is driving an output alarm
On. After detecting a fault, the internal circuitry will set the output data to
the appropriate safe state, as defined by the module data table. Safe state
control may be adapter dependent. The input and output indicators are on
the field side of the isolation path, and display the logic state of the actual
microcontroller input and output.
The status indicator initially powers up as solid green, indicating the power
supply is operating and internal diagnostic tests are being performed. After
a successful power up test, the indicator remains green. The indicator turns
red in about 1.5 s if there is an internal diagnostics error. The module is
operating correctly when the green OK indicator is on.
A red OK indicator shows that the module is in a Faulted condition
(internal error).
Diagnostics
The frequency input module returns diagnostics to the PLC processor in
word 5 of the BTR file. These diagnostics give you information on the
status or condition of the module.
BTR Word 5
Indicator
Condition
Operating Description
Input (0, 1)
(Freq, or Gate)
Off (Dark)
Input Turned Off, Input Not Used, or Wire Disconnected
On (Yellow)
Input Turned On (Active High or Active Low if Inverted)
Fault (F)
(Freq, or Gate)
Off (Dark)
Wire Connected, Normal Operation or Detection Disabled
On (Red
Flashing)
Wire Disconnected, Fault Condition (for IEC 1+ Proximity switch
or switch contacts with shunt resistor)
Output Alarm
(0, 1)
Off (Dark)
Output Alarm Turned Off
On (Yellow)
Output Alarm Turned On (Logic Drive On)
Status (OK)
Off (Dark)
24V Power Turned Off, or 5V Logic Power Problem
Solid Green
Module OK, Normal Operating Mode
Solid Red
Module Fault, Outputs Disabled
FREQ
GATE
OK
0
FREQUENCY INPUT 2 CHANNEL
1
1794-IJ2
A
llen-Bradley
E
B
F
0
F
FREQ
GATE
1
F
1
F
OUT
0
OUT
1
C
D
A
A =
Input indicator.
B =
Insertable label for writing individual I/O assignments.
C =
Wire-Off Fault indicator.
D =
Output indicator.
E =
Power/status indicator - indicates power applied to module and status of module.
1794-IJ2 shown
15
14
13
12
11
10
09
08
07
06
05
04
03
02
01
00
word 5
See Table for diagnostics
44760
Input
Word
Bit
Definition
Word 5
Bits
00 - 03
Diagnostic Status - indciates the response from the module; a normal or
non-normal operating condition.
Bit
03
02
01
00
0
0
0
0
0 = Normal Operation (No Failure)
0
0
0
1
1 = Calibration Failure
0
0
1
0
2 = Configuration Failure
A Minimum Frequency Sample Time value other
than 0-9 was selected.
0
0
1
1
3 = Message Failure
0
1
0
0
4 = Lead Break Detection Hardware Failure
0
1
0
1
5 = Major Hardware Failure
0
1
1
0
6 = EEPROM Failure
0
1
1
1
7 = RAM Failure
1
0
0
0
8 = ROM Failure
1
0
0
1
9 = Calculation Failure
The actual Frequency is greater than 32,767 Hz or
3,276.7 Hz (overange). The scaled Frequency is
greater than 32,767 Hz or 3,276.7 Hz (overange).
The % Full Scale calculation (based on Maximum
Frequency) is > 3,276.7%.
1010 - 1111
10 - 15 = Not used
Specifications - Frequency Input Module, Cat. Nos. 1794-IJ2, 1794-IJ2K, and
1794-IJ2XT
Input Specifications
Number of input
channels
2
Number of inputs per
channel
2 - Frequency and Gate (gate used to establish direction)
Input frequency
Maximum - 1-32 kHz w/sine wave; 1-32 kHz w/square wave input
Frequency value
Maximum 32,767 or 3,276.7 (dependent on range)
Input pulse width
20
μ
s
Resolution/Accuracy
Refer to Resolution/Accuracy table
On-stage voltage, min
10V (24V IEC+1 proximity, encoder input or switch inputs)
On-state voltage, nom
(selected by terminal
base connections)
50 mV AC, 28V AC peak - Extended Magnetic Pickup
500 mV AC, 28V AC peak - Magnetic Pickup
< 3V - Vortex Flowmeter low range
> 6V - Vortex Flowmeter high range
24V DC IEC+1 proximity or encoder input
24V DC Contact Switch input
On-state voltage, max
Limited to isolated 24V DC power supply maximum
On-state current
minimum
nominal
maximum
2.0 mA
9.0 mA
10.0 mA
Off-state current, min
1.5 mA into 24V DC IEC+ terminal
Off-state voltage, max
5.0V DC on 24V DC IEC+1 terminal
Wire-off detection
0.4 mA for proximity, encoder or contact switch with 50 k
Ω
shunt resistor
Frequency input
impedance
>5 K
Ω
for 50 mV Extended Magnetic Pickup
>5 K
Ω
for 500 mV Magnetic Pickup
>10 K
Ω
for 3V Vortex Flowmeter low range
>10 K
Ω
for 6V Vortex Flowmeter high range
>2.5 K
Ω
for 24V DC IEC+1 proximity or encoder input
>2.5 K
Ω
for 24V DC Contact Switch input
Gate input impedance
>5 K
Ω
for 50 mV Extended Magnetic Pickup
>5 K
Ω
for 500 mV Magnetic Pickup
>2.5 K
Ω
for 24V DC IEC+1 proximity or encoder input
>2.5 K
Ω
for 24V DC Contact Switch input
Output Specifications (meets IEC 1A 24V DC output specifications)
Number of outputs
2 isolated
Output voltage source
Customer supplied
Output voltage
minimum
nominal
maximum
10V DC
24V DC
31.2V DC
Off-state voltage, max
31.2V DC
On-state current
1 mA per output minimum
1.0 A per channel sourced out of module maximum
Current Limited - All outputs can be on simultaneously without derating
Surge current
2 A for 50 ms, repeatable every 2 s
Off-state leakage
Less than 300
μ
A at 31.2V DC maximum
