Series-DHII

Supported Applications

The Dwyer Series DHII Digihelic® II is a differential pressure controller designed for measuring air and non-combustible, compatible gases. The unit features a 4-digit backlit LCD display and provides control via two SPDT relays alongside an analog output.

• Differential pressure monitoring in HVAC systems
• Process value retransmission via Modbus RTU RS485 serial communication

Operating Conditions & Performance

The Series DHII operates within ambient and process temperature ranges of 32 to 140°F (0 to 60°C). Accuracy is specified as ±0.5% at 77°F (25°C) including hysteresis and repeatability after a 1-hour warm-up period. The response time is 250 ms with dampening set to 1.

• Enclosure Rating: NEMA 4 (IP66)
• Housing Material: Aluminum, glass
• Burst Pressure Limits by Range: • Ranges ≤ 2.5 in. w.c.: 2 psi • 5" to 100": 5 psi or 9 psi depending on range (see specific model)

Measurement Envelope

The series supports multiple differential pressure ranges, including unidirectional and bidirectional spans:

• DH-002: 0 - 0.1 INWC
• DH-004: 0 - 1.0 INWC
• DH-006 to DH-010: Ranges from 5" to 100" INWC (unidirectional)
• DH-012 to DH-017: Bidirectional ranges including +/- 0.25, +/- 0.5, +/- 1.0, +/- 2.5, +/- 5.0, and +/- 10 INWC

Electrical & Output Specifications

The controller accepts power from 100 to 240 VAC (50 to 400 Hz), 132 to 240 VDC, or 24 VDC ±20%. It provides a 4-20 mA DC output into a maximum load resistance of 900 OHMS. Two SPDT relays are available for control actions.

Configuration Options

The Series DHII is configurable across several parameters to meet specific installation needs:

• Housing & Mounting: Vertical mounting with 1/8 female NPT process connections. Optional A-438 Bracket Mounting Diagram available.
• Electrical Connections: Euro type removable terminal blocks with watertight conduit fittings for 1/2" watertight conduit.
• Communication: Modbus RTU RS485 at 9600 Baud, 8 data bits, no parity, 1 stop bit. Factory default address is 50 (32h).
• Display & Control Logic: Supports Single Set Point, Two Set Point, or Set Point/Alarm control types. Display units configurable for INWC, FTWC, MMWC, CMWC, PSI, INHG, MMHG, MBAR, PA, KPA, HPA, OZIN, SFPM, M/S, SCFM, and M^3H.
• Advanced Functions: Includes peak/valley tracking, alarm delay (0-100 seconds), security levels 1–4, and maintenance mode for set point adjustments without affecting the process display.

Key Product Differences

Variants within the Series DHII differ primarily by their measurement range. The series includes models with unidirectional ranges (e.g., DH-001 through DH-010) and bidirectional ranges centered at zero (e.g., DH-011 through DH-017). All variants share the same NEMA 4 enclosure, dual relay output structure, Modbus RTU communication protocol, and power supply options. Specific burst pressure ratings vary by range; for example, models with ranges ≤ 2.5 in. w.c. have a limit of 2 psi, while higher ranges such as 100" INWC support up to 9 psi.