Rockwell Automation 61C351 2-In/2-Out 4-20 mA Analog Rail Module - Manual (Page 13)

2Ć3
The faceplate of the module contains three electrical connectors
labeled Input", Analog I/O", and Input Power" (reading top to
bottom). The top connector is used for connection to the I/O port. A
cable (M/N 45C5) is provided for this purpose. The second
connector, labeled Analog I/O", is a numbered, 12Ćpoint removable
plug connector with screwĆtype terminal points. Three successive
terminal points are reserved for each channel's connection to
external hardware. The top 6 points are reserved for the two output
channels (channel 0 and channel 1) and the bottom 6 are reserved
for the two input channels (channel 2 and channel 3). The Analog
I/O" terminals are designed for 14Ć22 AWG wire.
The third connector on the faceplate, also a removable plug
connector with screwĆtype terminal points, is used for input power.
The terminal points are labeled. The top two points are used if the
power source is 24 VDC. The bottom two points are used if the
power source is 120 VAC. The Input Power" terminals are designed
to use 14 AWG wire. A terminal stud for connecting a grounding
conductor is provided on the bottom of the rightĆhand mounting
flange.
The module faceplate also contains two LEDs, a mode switch, and a
fuse holder and fuse. The LED labeled PWR OK" indicates that the
I/O port, the external power source, and the internallyĆgenerated
voltages necessary for operation of the module are present. The
COM OK" LED indicates whether all four channels are successfully
communicating with the host.
The switch labeled Mode" is used to select between Local Head"
and Rail" mode. Note that the position of the switch is read only
once at the time power is turned on to the Reliance device that is
connected to the Analog Rail module. The mode will remain fixed as
long as this device is powered up.
As shipped from the factory, the fuse holder on the bottom of
the faceplate containsa .25A fuse for 120 VAC input power. If
input power will be 24 VDC, you need to replace the fuse with
the .75A fuse included along with the Analog Rail module.
2.2 Electrical Description
The Analog Rail module contains two analog input channels that
convert 4Ć20mA analog input signals to proportional values between
0 and 4095, equal to 12 bits of digital data. Input channels are
protected with a 32mA userĆreplaceable fuse. Input signals are
filtered through a second order lowĆpass filter. The module also
contains two output channels that can output 4Ć20mA analog
signals proportional to an input value of 0 to 4095. A userĆsupplied
power supply in series with the external hardware is required for the
output channels. Note that at a digital output = 4096, the output
rolls over to zero again. Negative output values cannot be
accommodated.
The A/D and D/A conversions are triggered by the actual I/O update
sequences. The conversion rate is therefore dependent upon the
scan time of the application task. See figure 2.2 for a typical output
circuit. See figure 2.3 for a typical input circuit.