Strategic Implementation: ALG616 vs. ALG626
Core Application Value
These isolated analog modules solve the problem of signal interference in large-scale industrial plants. Specifically, they excel in oil refineries and chemical processing facilities where long cable runs are common. Engineers specify the IC695ALG616 for standard high-density isolated voltage and current monitoring. In contrast, they choose the IC695ALG626 when they need to communicate with smart field devices. The ALG626 allows the PLC to read device IDs and calibration data directly. Thus, it significantly reduces the time required for instrument commissioning and maintenance.
Technical Insights and Specifications
Comparison Table: Key Technical Data
| Feature | IC695ALG616 | IC695ALG626 |
| Channels | 16 (Isolated) | 16 (Isolated) |
| HART Support | No | Yes (Full HART v5.0+) |
| Resolution | 16-bit | 16-bit |
| Input Types | Current / Voltage | Current / Voltage |
| Isolation | Channel-to-Channel | Channel-to-Channel |
| Backplane | RX3i PCI High-Speed | RX3i PCI High-Speed |
Signal Integrity and Isolation
Both modules utilize 1500V AC isolation to prevent ground loops between field sensors. Therefore, a massive surge on one channel will not damage the rest of the PLC rack. This feature is a mechanical necessity for systems spread across different power zones. Because the ALG626 includes HART modems on every channel, it can extract digital process variables without interrupting the 4-20mA analog signal. This practice ensures that the controller receives both the primary value and the device health status simultaneously.
Field Installation and Maintenance Guide
Wiring and Terminal Block Selection
Field experience indicates that high-density modules require precise cable management to avoid terminal overcrowding. During installation, you should use the IC694TBBx or IC694TBSx extended terminal blocks for both modules. This practice provides the necessary clearance for 16 pairs of shielded twisted-pair wires. Proper grounding of the shields at the entry point of the cabinet is essential. As a result, the system maintains the high signal-to-noise ratio required for accurate 16-bit data conversion.
Software Configuration and HART Diagnostics
Field technicians must use Proficy Machine Edition to define the input range for each channel. For the IC695ALG626, you also gain access to HART pass-through features. This allows maintenance teams to configure field instruments remotely from the control room. Maintaining this digital link prevents unnecessary trips into hazardous areas to check sensor calibration. Furthermore, the ALG626 can trigger alarms based on internal device faults. This proactive reporting ensures that a degrading sensor is replaced before it causes a process shutdown.
Buyer’s Guide and FAQ
Can I replace an ALG616 with an ALG626?
Yes, the ALG626 is backward compatible in terms of wiring and basic analog function. However, you must update the hardware configuration in your PLC project to recognize the new module.
Does the ALG626 support all HART devices?
It supports standard HART 5, 6, and 7 protocols. Therefore, it is compatible with most modern transmitters from major brands like Rosemount, Endress+Hauser, and ABB.
Is an external power supply required?
The modules draw logic power from the RX3i backplane. However, you still need to provide a 24V DC loop supply for your field transmitters.
What is the main reason to choose the ALG616?
If your facility does not use smart HART instrumentation, the ALG616 is a more cost-effective choice for providing 16 channels of isolated high-speed analog input.
Are these modules compatible with the Series 90-30?
No, both modules require the PCI-based RX3i backplane. They will not function in older 90-30 or 90-70 racks.
