Series-SCD

Supported Applications

The Dwyer Series SCD DIN Rail PID Temperature/Process Controllers are microprocessor-based regulating devices designed for heating and cooling applications. These controllers function as master (SCD-1000) or slave (SCD-2000) units within a multi-loop system, where one master controller can be combined with up to seven slave controllers without additional wiring between them.

While primarily configured for temperature regulation using thermocouples and RTDs, the series supports universal inputs including DC linear voltage and current signals. The product overview notes that in specific configurations involving carbon monoxide transmitters (such as Dwyer GSTA or CMT200 series), the SCD controller can accept signal input to adjust set points for fan/damper operation and high gas concentration alarms, typically around 25 PPM with a high alarm near 100 PPM. For systems requiring integration with building management infrastructure, the controllers provide feedback of current process values, set points, and output status via RS-485 Modbus® communication.

Operating Conditions & Performance

The Series SCD operates within an ambient temperature range of 32 to 122°F (0 to 50°C). The controllers are designed for installation completely within a panel or process control enclosure, requiring a separate UL Listed enclosure. Power is supplied via isolated switching power at 24 VDC.

Performance specifications include the following measurement capabilities:

• Sensor Inputs: Thermocouple types K, J, T, E, N, R, S, B, L, U, and TXK; Platinum RTD (Pt100, JPt100); Linear DC inputs of 0–5V, 0–10V, 4–20mA, 0–20mA, and 0–50mV.
• Sampling Rate: Analog input at 0.15 sec; Thermocouple or Platinum RTD at 0.4 sec.
• Control Methods: PID, ON/OFF, Manual, and PID program control.

The controllers feature non-volatile memory backup to retain settings during power interruptions. For DC current input applications, a 250 Ω precision resistor is required as an accessory.

Configuration Options

Each controller in the series includes one universal input and two output groups: one relay output (standard) and one user-selectable auxiliary output. The available configurations are defined by the model number suffix:

• Master Controllers (SCD-10xx): SCD-1023, SCD-1033, SCD-1053, and SCD-1063.
• Slave Controllers (SCD-20xx): SCD-2023, SCD-2033, SCD-2053, and SCD-2063.

The auxiliary output options include:

• Voltage Pulse (Code 2): DC 12V with a maximum output current of 40 mA.
• Relay Output (Code 3): SPST, rated for 3 A @ 250 VAC resistive load.
• Current Output (Code 5): DC 4–20mA with a maximum load resistance of 5,000Ω.
• Linear Voltage Output (Code 6): 0–10 VDC with a minimum load resistance higher than 1,000Ω.

The linear voltage and current outputs can function as control output, alarm output, or retransmission output. The series supports RS-485 digital communication using the Modbus® RTU/ASCII protocol at baud rates from 2,400bps to 38,400bps.

Key Product Differences

The Series SCD distinguishes between Master and Slave units based on their role in a multi-loop configuration. The SCD-1000 series serves as the master controller (first position), while the SCD-2000 series functions as slave controllers installed in parallel, allowing up to seven slaves per master without external wiring for power or communication between them.

Model variations are further defined by the auxiliary output type selected. For example, models ending in "3" (e.g., SCD-1023) feature a relay as the second output group, whereas models ending in "5" provide a 4–20mA current loop and those ending in "6" offer a 0–10V linear voltage signal. All variants share identical physical dimensions of approximately 90 mm (H) x 60 mm (W) with DIN rail mounting capability.

Compliance certifications for the series include CE and cULus LISTED. Accessories such as the SCD-PS power supply, MN-1 USB/RS-485 converter, A-277 precision resistor, and SCD-SW configuration software are available to support installation and operation.