Series-651

Supported Applications

The Dwyer Series 651 is a low-cost temperature transmitter designed to accept standard platinum resistance sensors (Pt100) or ungrounded Type K thermocouples and convert the measurement into an industrial 4-20 mA current signal. The device accepts Pt100 RTDs conforming to BS1904 or DIN 43760 standards, as well as Type K inputs for models designated with the TC suffix.

Thermocouple models (Series 651TC) feature cold junction compensation and automatic upscale burnout. The transmitter is housed in a standard connecting block suitable for sensor head enclosure mounting or can be installed using an optional NEMA 4X Aluminum Transmitter Enclosure (Model A-709).

Operating Conditions & Performance

The Series 651 operates within specific ambient and storage temperature limits. The operating ambient range is 32 to 122°F (0 to 50°C), with a maximum storage temperature of 160°F (70°C). Ambient humidity ratings are specified as 0 / 95% non-condensing.

Performance specifications vary by input type:

• Accuracy: Models 651A offer ±0.2°C plus 0.2% reading; models 651TC provide ±0.1% FS plus cold junction errors.
• Response Time: Models 651A respond in 10 to 90% within 200 ms, while models 651TC achieve 70% response in 2 ms.
• Temperature Drift: Zero drift is typical at 0.02%/°C (0.09°F); Span drift is typical at 0.005%/°C (0.0036°F).

The transmitter requires a loop supply of 10 to 32 VDC and supports a maximum load resistance of 700 Ω @ 24 VDC.

Configuration Options

The series is configured for specific measurement ranges via model suffixes. The available variants cover the following temperature envelopes:

• Pt100 RTD Models (651A):
• Model 651A-10: 32 to 212°F (0 to 100°C)
• Model 651A-20: 32 to 392°F (0 to 200°C)
• Model 651A-40: 32 to 752°F (0 to 400°C)

• Type K Thermocouple Models (651TC):
• Model 651TC-01: 32 to 212°F (0 to 100°C)
• Model 651TC-02: 32 to 392°F (0 to 200°C)
• Model 651TC-04: 32 to 752°F (0 to 400°C)
• Model 651TC-06: 32 to 1112°F (0 to 600°C)

The transmitter is a 2-wire device with reverse connection protection. Electrical connections are made via screw terminals, supporting Pt100 sensors in either 2 or 3 wire configurations.

Key Product Differences

Differences between the two primary families within Series 651 include input sensor type and performance characteristics:

• Sensor Input: Models prefixed with "A" (e.g., 651A-10) are designed for Pt100 RTD inputs. Models prefixed with "TC" (e.g., 651TC-01) accept ungrounded Type K thermocouples.
• Accuracy Profile: The accuracy specification differs, with RTD models defined by a combination of degree Celsius and percentage of reading, while Thermocouple models are specified as a percentage of full scale plus cold junction errors.
• Response Speed: Type K thermocouple models exhibit significantly faster response times (2 ms) compared to Pt100 RTD models (200 ms).