The IS220PHRAH1B is a high-performance HART® Enabled Analog Input/Output module within the General Electric (GE) Mark VIe distributed control system. As an important member of the PHRA family, the IS220PHRAH1B is designed to communicate with the controller over single or dual I/O Ethernet networks while directly connecting to an analog input/output terminal board (such as the SHRA). It provides 10 channels of high-precision analog input and 2 channels of analog output for industrial process control. Its most significant highlight is that all 12 channels (10 inputs and 2 outputs) fully support transparent transmission of the HART (Highway Addressable Remote Transducer) communication protocol. This allows the control system to communicate digitally with field HART-enabled smart devices without affecting the standard 4-20 mA analog signals, enabling remote parameter configuration, diagnostic data retrieval, and device health management.
The module integrates a common processor board and a dedicated analog acquisition board. The processor board handles Ethernet communication, logic control, and HART protocol processing; the acquisition board is equipped with a 16-bit analog-to-digital converter (A/D) and a 14-bit digital-to-analog converter (D/A), ensuring extremely high signal conversion accuracy. The IS220PHRAH1B features a compact surface-mount design with small dimensions (8.26 cm x 4.19 cm x 12.1 cm) and plugs directly onto the companion terminal board, greatly simplifying wiring and installation within the control cabinet. Its operating temperature range is -30 to 65 °C, allowing it to adapt to harsh industrial environments ranging from extreme cold to high heat.
System Positioning and Architecture Integration
Within the network architecture of the Mark VIe control system, the IS220PHRAH1B serves as a key component of the distributed I/O layer, positioned between the field devices and the controller. Its working mode is straightforward: the module plugs directly onto the SHRA (or compatible) terminal board via a DC-62 pin connector on its back, requiring no additional cables; it connects to the I/O Ethernet network via two RJ-45 Ethernet ports (ENET1 and ENET2) on its side, exchanging real-time data with the R, S, and T control sections of the controller; a 3-pin power connector supplies 28 V DC operating power.
The IS220PHRAH1B supports only simplex operation, meaning one terminal board connects to only one I/O module. For high-reliability applications requiring Triple Modular Redundancy (TMR), three independent SHRA terminal boards and PHRA modules can be configured, each corresponding to the R, S, and T control sections, with 2-out-of-3 voting performed by the application software.
Detailed Core Functions
1. Flexible Multi-Type Analog Inputs
The IS220PHRAH1B provides 10 high-precision analog input channels, flexibly configurable to accommodate different field transmitter types:
Channels 1 through 8: Can be independently configured for ±5 V DC voltage input or 4-20 mA current loop input. When configured for current input, a precision 250 Ω burden resistor located on the terminal board converts the current signal into a 1-5 V DC voltage signal, which is then acquired by the module's 16-bit A/D converter.
Channels 9 and 10: Can be configured for 4-20 mA current input or ±1 mA low-current input, providing a flexible connection method for specialized sensors.
All analog input signals first pass through a second-order, passive, low-pass filter network (with poles at 12.5 Hz and 48.3 Hz), effectively suppressing high-frequency noise. Additionally, users can independently configure a digital low-pass filter for each channel via the ToolboxST software, with selectable cutoff frequencies of 0.75 Hz, 1.5 Hz, 3 Hz, 6 Hz, or 12 Hz, to further eliminate field interference.
The measurement accuracy of the module is outstanding: better than 0.1% of full scale over the entire 0 to 60 °C temperature range, with typical accuracy at 25 °C reaching 0.007% of full scale. The A/D converter sampling rate is 200 Hz per channel (5 ms scan period), fully meeting the real-time requirements of process control. Furthermore, the module features up to 60 dB of AC common-mode rejection (at 60 Hz) and 80 dB of DC common-mode rejection, with a common-mode voltage range of ±5 V, maintaining signal integrity even in environments with strong electromagnetic interference.
2. Dual-Channel High-Precision Analog Output
The IS220PHRAH1B provides two 4-20 mA current outputs, driven by a 14-bit D/A converter. The output compliance voltage reaches 18 V, with a maximum load capability of 800 Ω. Current detection circuits are configured for each output, both internal to the module and on the terminal board: the internal detection loop is used for closed-loop control, while the detection loop on the terminal board (via a small burden resistor) is used for diagnostic monitoring of the output status. This dual-sensing mechanism ensures the accuracy of the output current and rapid fault discovery.
Each analog output is equipped with a "suicide relay." If the system diagnostics detect a severe fault on the output channel, this relay can force the output circuit to open, returning the controlled object to a fail-safe state. The status of the suicide relay is continuously monitored; any discrepancy will generate a diagnostic alarm.
3. Full-Channel HART Communication and Asset Management
A core advantage of the IS220PHRAH1B, distinguishing it from ordinary analog I/O modules, is its full-channel support for the HART protocol. The 12 HART channels (10 inputs and 2 outputs) are assigned to two HART modems (Modem A and Modem B). Modem A handles input channels 1-5 and output 1; Modem B handles input channels 6-10 and output 2.
Each HART channel can simultaneously transmit the standard 4-20 mA analog signal and the Frequency-Shift Keying (FSK) digital signal superimposed on it. The control system can remotely read HART data from field devices via Ethernet and the ToolboxST software—including device manufacturer ID, device type, software/hardware revision, extended status bytes, and up to four dynamic variables (PV, SV, TV, FV). Simultaneously, an Asset Management System (AMS) can collect device diagnostic information over the same path in real time, enabling predictive maintenance.
The update rate of HART data depends on the number of active channels per modem: if only one channel is in use, the data is updated roughly once per second; if all six channels are communicating, approximately eight seconds are required to complete a full polling cycle of all channels. For critical real-time control signals, the priority and mode of HART communication can be flexibly configured via the ToolboxST software to ensure that the normal response of the analog signal is not affected.
4. Comprehensive Diagnostics and Self-Test Functions
The IS220PHRAH1B offers extensive power-up and online diagnostic functions, ensuring that any potential fault is detected and reported in a timely manner:
Power-Up Self-Test: At each power-up, the module automatically performs a comprehensive check of RAM, flash memory, Ethernet ports, and processor board hardware.
Continuous Power Monitoring: Monitors the internal 18 V and 28 V power supply voltages in real time; any anomaly is immediately reported.
Electronic ID Verification: At power-up, reads the electronic ID information from the terminal board, acquisition board, and processor board to verify hardware set matching, and checks that the application code loaded from flash memory is correct for the hardware set.
Analog Input Hardware Limit Checking: Each configuration type has preset hardware high/low limits. If an input signal exceeds this range, the corresponding channel is immediately removed from the scan sequence, and a composite diagnostic alarm for the entire board (L3DIAG_PHRA) is generated.
Analog Input System Limit Checking: Users can freely set high/low alarm limits via ToolboxST and select whether they latch. Exceeding a limit triggers an alarm.
A/D Converter Health Check: Precision reference voltages are included in each scan. Measured values are compared against expected values to confirm the health of the analog-to-digital converter circuits.
D/A Converter Health Check: The output current on the terminal board is converted to a voltage by a small sense resistor and read back by the module. This is compared to the commanded current to confirm the health of the digital-to-analog converter and output circuit.
Suicide Relay Status Monitoring: Continuously compares the commanded state of the suicide relay with its feedback indication; any mismatch annunciates a fault.
HART Communication Status Monitoring: Each HART channel provides a communication status signal (CommStat) and a device status signal (DevStat), recording checksum errors, framing errors, overrun errors, and device-side faults in detail.
All diagnostic signals can be individually latched and reset via the RSTDIAG signal once the fault clears.
5. Convenient Installation and Configuration
Installation of the IS220PHRAH1B is exceptionally simple. First, securely mount the SHRA (or compatible) terminal board to a DIN rail or cabinet panel. Then, align the DC-62 pin connector of the IS220PHRAH1B module directly with the connector on the terminal board and plug it in. Finally, secure the module using the threaded studs adjacent to the Ethernet ports in conjunction with the mounting bracket supplied with the terminal board, ensuring no right-angle force is applied to the connector. This adjustment is typically required only once in the product's lifetime. Connect one or two Ethernet cables (for a redundant configuration, the standard practice is to connect ENET1 to the network associated with the R controller), and plug in the power connector (hot-plugging is supported; the module has soft-start capability). Hardware installation is then complete.
The module requires no hardware jumpers or switch settings. All configuration is performed through GE's ToolboxST application software. In the ToolboxST Component Editor, the user can set the input type, range, engineering unit conversion, software filter frequency, and HART device parameters for each channel. Once the modified configuration is downloaded to the controller, it takes effect immediately.
Typical Application Scenarios
The IS220PHRAH1B is widely applicable in various power generation and process industrial control scenarios, such as:
Steam Turbine and Auxiliary Equipment Control: Connects to 4-20 mA transmitters for lube oil temperature, bearing vibration, steam pressure, valve position feedback, etc., while outputting 4-20 mA control signals to valve positioners.
Gas Turbine Fuel Control: Acquires gas/liquid fuel flow, pressure, and temperature signals, and outputs control current to the fuel control valve.
Centralized Process Variable Monitoring: All HART-enabled transmitters (temperature, pressure, level, flow) can have their parameters centrally managed remotely through this module, eliminating the need for additional multiplexers or handheld communicators.
Asset Management: Works with AMS software to capture fault codes, wear status, calibration drift, and other information from each device in real time, enabling an upgrade from preventive to predictive maintenance.
