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| Type: | Dual Hole Terminals |
| Material: | Silver-Plated Copper |
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Product Introduction: Rosemount™ 644 Temperature Transmitter Terminal Configurations
1. Overview of Terminal Features
The Rosemount™ 644 Temperature Transmitter (models 644H for single-input and 644S for dual-input) is designed for industrial temperature monitoring with HART® protocol support (Version 5 or 7). Its terminal configuration ensures flexibility for diverse sensor types, including RTDs (2/3/4-wire), thermocouples, mV, and Ohm inputs. Key features include:
Compact Design: Fully encapsulated electronics in silicone for long-term reliability.
Safety Compliance: IEC 61508 SIL 2 certification option for hazardous areas.
Display Options: Standard LCD or advanced Local Operator Interface (LOI) with extended temperature tolerance (-40 to 85°C)
2. Terminal Functions and Layout
2.1 Power Terminals (Position )
Function: Provide 12-42.4 VDC power via signal lines.
Requirements:
Minimum 12.0 VDC to maintain operation; voltage below 9 VDC during configuration may damage the device.
Wire gauge ≥20 AWG copper to minimize voltage drop
Safety: Avoid AC voltage or >42.4 VDC to prevent equipment failure.
2.2 Input Signal Terminals
644H (Single-Input):
Four terminals (Position ) for one sensor channel. Supports all sensor types via configurable wiring
644S (Dual-Input):
Two sets of three terminals (Positions ), each for independent sensor inputs (e.g., dual RTDs or thermocouples)
2.3 Display Interface (Position )
A dedicated pin for connecting an optional LCD or LOI display. Users can verify display presence by inspecting the terminal compartment.
2.4 Hardware Alarm Switch
Dial labeled "L" (Low) or "H" (High) to set fault-mode behavior (e.g., output saturation during sensor failure)
| erminal Type | Function | Technical Specifications |
| Power Terminals | Power supply input | - Voltage Range: Min. 12.0 Vdc (ensure voltage ≥12 Vdc at terminals) - Max. Voltage: 42.4 Vdc (exceeding this may damage the device) - Wire Suggestion: Standard copper wire with adequate gauge to minimize voltage drop |
| Sensor Input Terminals(Single Input: 644H) | Connects to single RTD/T/C/mV sensor | - Compatible Inputs: RTD (2/3/4-wire), thermocouple (T/C), millivolt (mV), ohms - RTD Lead Resistance: ≤60 Ω per wire for 3/4-wire RTDs (no recalibration needed) |
| Sensor Input Terminals(Dual Input: 644S) | Connects to dual RTD/T/C sensors (two independent channels) | - Same as above- Critical Note: Avoid using two grounded thermocouples simultaneously for dual inputs; use one grounded + one ungrounded or a dual-element T/C |
| Display Interface | Connects to optional LCD display | - Purpose: For local temperature readout (display module not always installed) - Handling: Use caution when handling pins; |
| Fault Mode Selector | Hardware alarm setting for output during sensor failure | - Positions: - H (High): Output defaults to 21.9 mA or high alarm state. - L (Low): Output defaults to 3.8 mA or low alarm state |
3. Electrical Specifications
Power Supply: 9-32 VDC (recommended 12-42.4 VDC for stable operation)
Input Resistance Limits:
For 3/4-wire RTDs: Lead resistance ≤60 Ω (equivalent to 6,000 ft of 20 AWG wire). Exceeding this requires recalibration
For 2-wire RTDs: Errors escalate with lead length (>3 ft for 20 AWG induces ~0.05°C/ft error)
Isolation: Sensor and power terminals are electrically isolated to prevent ground loops.
4. Wiring Guidelines for Sensors
4.1 Thermocouple/mV Inputs
Direct Connection: Use thermocouple extension wires for long distances.
Shielding: Shielded cables mandatory; ground shields at the power source only (Option 1)
Avoid Grounded Thermocouples in Dual Inputs: Prefer one grounded and one ungrounded thermocouple to mitigate noise
4.2 RTD/Ohm Inputs
2-Wire RTDs:
High error susceptibility due to lead resistance. Limit lead length to <3 ft (20 AWG).
3-Wire RTDs:
Use identical wire gauges to balance resistance. Errors persist but are minimized.
4-Wire RTDs:
Optimal accuracy; lead resistance is auto-compensated. Unused leads must be insulated
4.3 Grounding Practices
Unshielded Sensors (RTD/mV):
Option 1: Shield connected to transmitter housing; isolated from external grounds.
Grounded Thermocouples:
Option 4: Shield grounded at the sensor; sensor/power shields isolated from transmitter housing
5. Safety and Compliance
Explosion Protection:
Terminal covers must be fully sealed in hazardous areas. Never remove covers while powered in explosive atmospheres
Electrocution Prevention:
Terminal contacts may carry high voltage during sensor faults. Use insulated tools during maintenance
Certifications: ATEX, IECEx, and FM approvals for hazardous locations (see manual for region-specific certifications)
6. Installation Best Practices
Mechanical Mounting:
Install at the highest point of piping to prevent moisture ingress
Electrical Connection Sequence:
Secure wires to labeled terminals (torque: 6 in-lbs/0.7 N-m).
Verify polarity for non-HART versions (HART-compatible models are polarity-insensitive)
Post-Installation Checks:
Validate configuration via HART communicator or LOI.
Test for lead resistance errors using device diagnostics
7. Troubleshooting Common Issues
Signal Drift:
Check lead resistance for 2/3-wire RTDs; recalibrate if >60 Ω.
Communication Failure:
Verify HART version compatibility (V5/V7 switchable via LOI)
Display Malfunction:
Inspect display-interface pin for damage.
Conclusion
The Rosemount 644's terminal design balances versatility with robust safety, supporting diverse industrial temperature applications. Adherence to wiring specifications and grounding protocols is critical to exploit its ±0.05% accuracy and SIL 2 capabilities. For exhaustive specifications, consult the [Reference Manual (00809-0206-4728)
The packaging and transportation of instrumentation in global trade hinges on a synergy of advanced materials, rigorous testing, regulatory compliance, and smart logistics. By adopting hybrid structural designs, leveraging real-time monitoring technologies, and prioritizing sustainability, exporters can ensure the safe, efficient, and cost-effective delivery of precision instruments. Continuous innovation in materials science and IoT integration will further redefine industry standards, enhancing resilience in an increasingly interconnected market.
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Q: What is the delivery time?
A: Our delivery time is within 3-7 days after we get your payment;
for large qty mass orders, the time should be confirmed again for you.
Q: How about your package?
A: Do not worry about the package, we have rich experience in packing, and all our package is wooden case package.
Q: How about the payment terms?
A: You can choose T/T.
Q: Do you provide samples?
A: Yes, we have materials in stock to help you to get the samples as soon as we can.
Q: What is the MOQ?
A:1PC.
Q: Can I get a lower price if I order large quantities?
A: Yes, cheaper prices with more bigger size orders.
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