Description
The Honeywell 05701-A-0302 (originally manufactured under the Zellweger / Sieger brand names) is a single-channel gas detection controller card designed for the Series 57 (System 57) modular rack platform. This 3U plug-in card is factory-configured with an onboard catalytic sensor drive module to interface directly with 3-wire combustible gas sensors. The card processes low-mV bridge signals, manages localized alarm voting thresholds, and provides real-time concentration readouts via an integrated multi-segment front panel display. Because each card operates independently on the shared rack backplane, a single-point failure remains isolated to its specific channel.
Commercial Availability & Procurement
- Condition: Factory Sealed / New Surplus (Legacy Product Line — original anti-static packaging verified) or Refurbished (Fully certified on gas-loop simulators)
- Warranty: 12-Month Comprehensive Operational Warranty
- Availability: In Stock / Limited Legacy Quantities Remaining
- Estimated Lead Time: 1–3 business days via DHL Express or FedEx Priority
- Pricing Policy: Subject to global stock level fluctuations and specific firmware revision requirements. Contact our safety systems division for a binding, itemized quote.
Technical Specifications
| Parameter | Specification |
|---|---|
| Manufacturer | Honeywell Analytics (Sieger / Zellweger) |
| Model Number | 05701-A-0302 |
| Platform | System 57 / 5701 Series |
| Input Type | 3-Wire Catalytic Bead (Combustible Gas Sensor) |
| Sensor Bridge Current | Selectable via solder links (70 mA to 283 mA range across 4 stages) |
| DC Supply Voltage | 18 V DC to 32 V DC |
| Power Consumption | 3.75 W typical (including active catalytic sensor load) |
| Display Type | Four-part LCD (25-segment analog bar graph, 4-character digital readout) |
| Front Panel LEDs | A1, A2, A3 (Alarms), Fault (Yellow), Inhibit (Yellow) |
| Push-Button Interface | Single dual-function Reset / Card Select tactile switch |
| Alarm Setpoint Resolution | Adjustable in 1% Full Scale Deflection (FSD) increments |
| Form Factor | 3U card structure; 112 mm (H) × 25 mm (W) × 170 mm (D) |
| Weight | 165 g |
| Operating Temperature | −5 to +55 °C (+23 to +131 °F); 0 to +55 °C for ATEX installations |
System Integration & Real-World Field Constraints
Sensor Bridge Current and Solder Links (LK1–LK3)
The 05701-A-0302 features an onboard drive circuit with three physical solder links (LK1, LK2, LK3) used to set the constant operating current for the external catalytic bead sensor.
Critical Field Setup: You must match these links precisely to the sensor’s required millivolt bridge characteristics before sliding the card into a live rack backplane. Setting the bridge current too high will instantly burn out the platinum filament in a new catalytic sensor pellistor upon power-up. Conversely, under-driving the sensor leads to severe calibration drift and non-linear response curves in toxic or explosive gas atmospheres.
Calibration and Engineering Card Interfacing
This control card contains no manual potentiometers or tuning trim-pots. Zero and span calibrations cannot be performed directly on the front panel of the 05701-A-0302. All parameters must be adjusted electronically through a central Engineering Card (such as the 05701-A-0361 control module) or via configuration software attached to the rack’s communication bus.
- Commissioning Step: When installing a replacement card, navigate the Engineering Module menu to select the target card slot, then execute a “First-Time Span Calibration” to map the new card’s analog-to-digital converter (ADC) baseline to the specific field wiring resistance loop.
- RFI/EMC Shielding: Catalytic sensor circuits operate on low-voltage differentials. Ensure that the 3-wire sensor cable shield terminates cleanly at the Field Interface Card (FIC) grounding bus bar to prevent erratic fault alarms caused by handheld radio transceivers or nearby variable frequency drives (VFDs).
Hot-Swap Operational Risk
While individual channel cards are designed to slide into the backplane independently, hot-swapping a card into a live 19-inch chassis carries the risk of arcing on the edge pins. Always place the channel into “Inhibit” mode via the engineering module before physical extraction, or briefly isolate the rack’s 24 V DC power rail to eliminate the risk of corrupting adjacent operational channel configurations.
Frequently Asked Questions
Can a 05701-A-0302 card be reconfigured to accept a 4–20 mA loop transmitter input?
No. The hardware architecture of the 05701-A-0302 is physically populated with a catalytic bead bridge measurement circuit. To utilize a 3-wire or 2-wire 4–20 mA loop input transmitter (such as a Honeywell Searchpoint Optima or Sensepoint unit), you must procure a different variant, such as the 05701-A-0301 control card, which contains the specialized load resistor shunt configuration for standard loop currents.
What does a solid yellow “Inhibit” LED indicate, and how is it cleared?
The “Inhibit” LED indicates that the card’s alarm relay outputs and external voting matrix lines have been intentionally locked or suspended. This state is triggered during calibration, sensor maintenance, or system configuration via the engineering master card to prevent accidental facility shutdowns or false activations of deluge/siren systems. It can be cleared by exiting the calibration mode on the master engineering module or cycling the local reset switch if a latching fault cleared during a service window.
Why is the digital display reading lower than zero (“- – -“) after a cold start?
If the digital readout indicates a negative drift or a series of dashes below zero, the catalytic sensor elements are likely experiencing thermal stabilization lag or the ambient temperature has dropped below the baseline recorded during the last zero-calibration procedure. Allow the sensor to burn-in for at least 30 minutes after power-up. If the reading fails to normalize, perform a fresh zero alignment via the engineering panel using verified zero-air calibration gas.
