Description
Product Introduction & Engineering Value
Process instability isn’t always caused by the controller. In many mature Advant OCS installations, degraded analog output modules are responsible for drifting control valves, unstable VFD references, or inconsistent actuator response. The ABB CMA198 provides eight isolated analog current outputs for precise process control in legacy ABB automation systems.
Designed for the Advant OCS 200/400 family, the CMA198 interfaces with ABB controllers through the AF100 communication network. It continues to be an important spare part for plants extending the operational life of existing DCS installations while maintaining proven control strategies.
Technical Specifications
| Parameter | Specification |
|---|---|
| Manufacturer | ABB |
| Model | CMA198 |
| Product Type | Analog Output Module |
| System Family | ABB Advant OCS 200/400 |
| Output Channels | 8 |
| Output Signal | Active 4–20 mA |
| Resolution | 12-bit |
| Output Accuracy | ±0.15% of span |
| Maximum Load | 750 Ω per channel |
| Update Time | Approximately 10 ms per channel |
| Communication | AF100 compatible |
| Connector | 37-pin D-Sub |
| Power Consumption | Approximately 2.5 W |
| Operating Temperature | 0°C to +60°C |
Field Application & The “Trench” Experience
A pulp mill reported inconsistent stock flow despite stable controller calculations. Maintenance initially suspected sticking control valves, but valve testing showed normal operation. Trend analysis revealed that two analog output channels occasionally produced unstable current signals under load.
Replacing the aging CMA198 restored stable 4–20 mA output, eliminating flow oscillation without modifying the controller application or recalibrating the valve positioners. The maintenance outage finished ahead of schedule because only the I/O module required replacement.
Typical applications include:
- Catalytic cracking unit flow control valves
- Steam turbine governor analog control
- Chemical reactor dosing pump regulation
- Paper machine consistency valve positioning
- Variable frequency drive speed reference outputs
- CMA198
- CMA198
Transparency SOP: QA & Testing
Every module is inspected before shipment through a documented quality process.
- Verify the ABB model identification and hardware revision.
- Inspect the PCB, edge connector, and D-Sub interface for mechanical damage.
- Perform power-up verification using a compatible Advant OCS test rack.
- Measure all analog output channels for linearity and accuracy.
- Confirm overload and open-circuit diagnostics where applicable.
- Package the module in anti-static materials with impact-resistant protection.
Refurbished units undergo full functional testing before release.
The Veteran’s Tech Trap Guide
⚠️ Don’t replace the module before checking loop resistance.
A 4–20 mA output can appear faulty when excessive loop resistance prevents the signal from reaching the field device. Measure the total loop impedance before replacing hardware.
⚠️ Verify the field power arrangement.
The provides active current outputs. Connecting it to instrumentation designed for passive loop operation without reviewing the wiring diagram can create commissioning problems.
PRO TIP:
Before removing the existing module, record the output values under normal operating conditions. Comparing the replacement module against baseline process data is often faster than troubleshooting after startup.
⚠️ Inspect connector pins carefully.
Many intermittent analog signal issues originate from oxidized or loose 37-pin D-Sub connections rather than a failed output circuit.
Dynamic FAQ
Q1. What is the primary function of the ABB ?
The converts digital control commands into eight isolated 4–20 mA analog output signals for control valves, variable frequency drives, actuators, and other process equipment.
Q2. Which ABB systems use the ?
The module is designed for ABB Advant OCS 200/400 process automation systems utilizing the AF100 communication architecture. Compatibility should always be confirmed using the controller configuration.
Q3. What output accuracy does the provide?
The module provides 12-bit resolution with a typical output accuracy of ±0.15% of span, making it suitable for precision analog process control.
Q4. Are New Surplus modules genuine ABB products?
Yes. New Surplus inventory consists of unused original ABB hardware stored under controlled environmental conditions. Every module is inspected for identification, connector condition, and physical integrity before shipment.
Q5. Can the be replaced without modifying the controller program?
In most applications, yes. Since the functions as an analog output interface, replacing the module generally does not require changes to the controller logic. Output calibration and field wiring should still be verified during commissioning.
Q6. Is warranty available?
Yes. Both New Surplus and professionally refurbished modules are available with warranty coverage. Warranty duration depends on the supplied condition and is confirmed with the quotation.
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