Spectrum Controls 1734sc-IE2CH - Manual (Page 12)

1-4 Point IO™ 2/4 Channel Analog HART Module
User’s Manual Pub. 0300257-01 Rev. A
functions. If no faults are found during power-up diagnostics, the module status LED is
turned on.
After power-up checks are complete, the module waits for valid channel configuration
data. If an invalid configuration is detected, the module will generate a PLC fault. Once
a channel is properly configured and enabled, it continuously converts the input data to a
value within the range selected for that channel.
1.6.2 Module Operation
The 1734sc-IE2CH and IE4CH modules are single ended 4-20mA current sensing input
modules with HART master capability. Analog current is measured by sensing voltage
drop across an internal resistor. The nominal input resistance of individual channels is
250ohms. In the event of an over-current fault the module will protect the input circuitry
by increasing the input resistance to limit input current. Analog to digital conversion is
performed by a multiplexed Sigma-Delta ADC shared by all channels. A range of notch
filters as well as an averaging filter can be applied to analog inputs. All channels share a
common ground. Field power is provided on the terminal block to simplify wiring. The
1734sc-IE2CH and IE4CH have HART Primary Master capability. A dedicated HART
modem is used for each channel for maximum throughput. When HART functionality is
enabled on a channel the module will discover and establish communication with HART
revision 5 and greater devices. Once communication has been established the module
will automatically gather HART PV, SV, TV, FV data and monitor device status. The
modules provide a communication bridge to HART devices for Asset Management
Software and Ladder Programs via CIP messaging.
See the block diagram below.