Description
The ABB DP840 (3BSE028926R1) is an 8-channel, groupwise-isolated pulse counting and frequency measurement module belonging to the S800 I/O family. Operated within the System 800xA or Freelance DCS architectures, this module captures high-speed pulse streams from external transducers, proximity sensors, NAMUR-compliant devices, or digital encoders. It processes and serializes these metrics into accumulative count data or explicit frequency (speed) readings, passing the dataset back to the parent AC 800M or equivalent master controller via the ModuleBus interface.
Commercial and Availability Status
- Product Condition: New Original (Factory Sealed) or New Surplus / Bench-Tested Exchange
- Warranty: 12-Month Industrial Warranty
- Estimated Lead Time: 1–3 business days (Global express delivery available)
- Pricing Note: List pricing is indicative and varies based on global availability and active component demand curves. Contact our automation supply desk for a binding commercial quote.
Technical Specifications
| Parameter | Value |
| Model Number | DP840 |
| ABB Part Number | 3BSE028926R1 |
| I/O Type | Pulse Counter / Frequency (Speed) Input |
| Number of Channels | 8 independent, identical channels |
| Frequency Range | 0.5 Hz to 20 kHz |
| Counter Size | 16-bit accumulation register per channel |
| Transducer Signalling Levels | NAMUR, 12 V DC, 24 V DC |
| Signal Specification | 24 V DC Nominal (Acceptable operating range: 19.2 to 32 V DC) |
| Isolation | Groupwise isolation from system ground |
| Maximum Absolute Error | 500 ppm (= 0.05%) at PRIT = 10 ms (Under 16 years of crystal age) |
| Max Field Cable Length | 200 meters (218 yards) |
| Power Dissipation | 4 W maximum |
| Current Consumption | 115 mA at +5 V DC (ModuleBus), plus external field load |
| Redundancy Support | Yes (Supports dual-redundant mounting configurations) |
| Form Factor Dimensions | 45 mm (W) × 102 mm (D) × 119 mm (H) |
| Net Weight | 0.15 kg (0.33 lbs) |
| Protection Rating | IP20 (IEC 60529) |
| Hazardous Area Certs | Class 1 Div 2 cULus, ATEX Zone 2, CE, Marine (DNV, LR, BV) |
Engineering Deployment and Field Constraints
Channel Operating Modes
Each of the 8 channels can be individually tailored within the engineering workspace (e.g., Control Builder M) to perform distinct application profiles:
- Pulse Counting: Counts electrical transitions via a 16-bit hardware register. When the counter reaches 65,535, it rolls over naturally. Logic must account for this rollover cycle during volumetric accumulation or positioning logic.
- Frequency Measurement: Automatically samples incoming square or sinusoidal wave structures down to 0.5 Hz, making it suitable for low-speed turbine surveillance, flow meters, or rotational velocity sensing.
- Standard Digital Input (DI): Disables the high-speed processing circuits, enabling the channel to be read directly as a standard binary state indicator.
Termination Unit and Redundancy Pairing
Mechanical Compatibility: The DP840 utilizes mechanical keying code CF. It must be paired with compatible Module Termination Units (MTUs) such as the TU810V1, TU812V1, TU814V1, TU830V1, TU833, or the redundant-capable TU854 baseplate. Attempting to seat the module onto an incompatible MTU will damage the rear alignment pins.
Field Noise Isolation Guidelines: When operating close to the 20 kHz threshold, the 200-meter field cabling run must utilize twisted-pair, individually shielded cables. Keep the pulse signal runs clear of active VFD output rails or heavy multi-phase supply lines. Ensure the shield drain wire terminates directly to the MTU grounding bar. Floating or incorrectly grounded shields will distort the waveform, causing edge-trigger jitter and leading to over-counting errors or false loop diagnostic faults.
Frequently Asked Questions
Can the DP840 handle dual-phase quadrature encoder signals for direction sensing?
No. The DP840 handles independent single-phase pulse inputs or frequency tracking across its 8 channels. For bi-directional quadrature tracking (A/B phase offset processing), the application typically requires a specialized high-speed counter module such as the DP820.
How does the module react to a field sensor wire break?
The DP840 features built-in loop supervision and advanced on-board diagnostics. When configured for NAMUR style sensors, the board constantly monitors quiescent loop impedance. A short circuit or broken field wire drops the circuit outside permissible baseline windows, lighting the channel-level front Fault LED and signaling a diagnostic trip back to the host controller’s error logs.
Is it possible to hot-swap this module during active process execution?
Yes. If mounted on a redundant MTU setup (such as the TU854) or if working on a live backplane, the S800 system architecture permits “Hot Swap” (Removal and Insertion Under Power) capabilities. The redundant companion module instantly locks onto primary tracking duties, preventing signal dropouts. Ensure all ESD procedures are maintained throughout the swap.
