Description
Key Technical Specifications
- System Platform: Honeywell System 57
- Function: Sensor Input Only (No Relay Outputs)
- Channel Type: Single Channel Interface
- Signal Compatibility: 4-20mA or Catalytic (Verify Jumper)
- Mounting: System 57 19″ Rack or Wall Mount
- Cable Interface: 2.5mm / 14 AWG Terminals
- Power: Backplane 24V DC
- Diagnostics: LED Status Indicators
- Communication: Backplane Serial Bus
- Configuration: Jumper Selectable
- Condition: New Surplus / Refurbished Only
- Cross Reference: 05701-A-0325 (DC Input), 05701-A-0301 (Control Card)
Product Introduction
System 57 racks don’t like surprises. You pull a card, the new one has relays, and suddenly your exhaust fan starts cycling because the backplane is feeding 24V to a coil you didn’t expect. The 05701-A-0326 is the “quiet” version of the interface card: it reads the sensor, conditions the signal, and talks to the control card, but it has zero relay outputs. No switching. No surprises. Just raw sensor data for the main controller to decide on.
Why does this distinction matter? Because Honeywell sold at least three variants of this form factor. The -0325 has DC inputs, the -0301 is a full control card with display, and the -0326 is strictly a signal conditioner. If you grab the wrong suffix, you’re either missing functionality or risking a short circuit. Honestly, for monitoring-only points where the DCS handles the trip logic, this card is perfect. But verify the jumper block matches your old one. Honeywell changed the 4-20mA vs. catalytic selection between production runs.
Troubleshooting Quick Reference
| Fault | Cause | Relevancy | Quick Check | Fix |
|---|---|---|---|---|
| No Sensor Reading | Jumper Mismatch | 90% | Compare jumper block to old card | Reset jumpers to match original config. |
| Erratic 4-20mA | Loose Terminal | 85% | Torque check sensor wires | Retorque to 0.5 Nm; check for oxidized copper. |
| Backplane Comm Fail | Bent Pin | 75% | Inspect gold fingers with flashlight | Straighten pins; clean with IPA. |
| Sensor Overrange | Wrong Range Jumper | 60% | Verify sensor type vs. card config | Confirm catalytic vs. 4-20mA setting. |
| LED Off | Backplane Power | 95% | Measure backplane 24V at slot | Check PSU or adjacent card short. |
Honeywell 05701-A-0326
Application Scenarios & Pain Points
- Offshore Platform Gas Detection: Space is tight. You need sensor monitoring without local relay chatter. The -0326 handles the signal; the main controller 20 miles away makes the trip decision. No local noise, no local power draw for coils.
- Wastewater Treatment H2S Monitoring: Corrosive environment kills relay contacts in 6 months. This card has no relays to pit. Signal goes to the PLC; PLC drives a solid-state contactor. Card survives; relays don’t.
- Pharma Cleanroom O2 Monitoring: No sparking allowed. Relay arcs are a no-go in classified areas. This card is purely electronic. Zero ignition risk. Perfect for nitrogen purge monitoring.
Compatible Replacement Models
- ✅ Drop-in Replacement: 05701-A-0326. Exact match. Same jumper map, same no-relay config. Cost: ~998–2,500 surplus depending on vendor.
- ⚠️ Software Compatible: 05701-A-0325. DC Input version. Same form factor, same backplane, but different internal conditioning. Requires jumper reconfiguration. Labor: 1-2 hours + loop check. Verify sensor type first.
- ❌ Hardware Incompatible: 05701-A-0301. Full Control Card with LCD and relays. Different internal architecture, different backplane power draw. Do not substitute unless you need local display and are prepared for higher power consumption.
