Overview
The Dwyer DHC-002 is a Series DHC Digihelic differential pressure controller — a 3-in-1 instrument that combines a digital display gage, two control-relay switches, and a transmitter with both current and voltage outputs in a single device. This model covers a 0-0.25 in w.c. unidirectional range and can read pressure, air velocity, or volumetric flow in a range of engineering units. Replacing three separate instruments with one unit cuts inventory, installation time, and cost.
Best for
- SCFM duct flow, filter status, and duct or building static pressure
- Damper and fan control with two adjustable SPDT relays
- BACnet MS/TP or Modbus RTU building automation integration
- Applications needing display, alarm/control, and a transmitted signal in one device
Warranty
Backed by Dwyer's standard product warranty against defects in materials and workmanship; refer to Dwyer's Terms and Conditions of Sale for details. ZOT Supply is an authorized Dwyer distributor offering fast nationwide and international shipping. Field calibration and Dwyer Calibration Services are available.
Key Features
3-in-1 Instrument
Digital gage display, two SPDT control relays, and a 4-20 mA plus voltage transmitter combined in one device.
±1.5% FSO Accuracy
Full-scale accuracy for this 0-0.25 in w.c. range, with field-adjustable zero and span to maintain it over time.
Pressure, Velocity & Flow
Reads differential pressure, air velocity, or volumetric flow (SCFM / m³/h) in multiple selectable engineering units.
Dual SPDT Relays
Two control relays with adjustable trigger and reset points and selectable direct or reverse action for damper, fan, or alarm control.
BACnet & Modbus
Selectable BACnet MS/TP or Modbus RTU communication for direct integration with the building automation system.
Field Calibration
Menu-driven zero and span calibration lets you maintain accuracy in the field without returning the unit.
Technical Specifications
| Specification | Value |
|---|---|
| Pressure Range | 0-0.25 in w.c. Unidirectional |
| Service | Air and non-combustible, compatible gases |
| Accuracy | ±1.5% FSO (this range) |
| Process Modes | Pressure, Velocity, Flow |
| Output Signal | 4-20 mA (4-wire); 0-10 V, 0-5 V, 1-5 V, 2-10 V selectable (4-wire) |
| Communication | BACnet MS/TP or Modbus RTU |
| Control Relays | 2 SPDT, 1 A @ 30 VAC/VDC, adjustable deadband |
| Display | Backlit LCD with LED setpoint indicators |
| Power Requirements | 12-28 VDC or 12-28 VAC (50-400 Hz), 3 VA max |
| Stability | < ±1% / year FSO |
| Temperature Limits | -4 to 158°F (-20 to 70°C) |
| Pressure Limits | 6 psi max (ranges > 1 in w.c.); 3.6 psi max (≤ 1 in w.c.); 6 psi burst |
| Response Time | 400 ms (damping set to 0) |
| Process Connections | 1/8 in female NPT ports on side and back |
| Electrical Connection | 15-pin male HD D-sub; 18 in 15-conductor cable included |
| Housing Material | Polycarbonate |
| Enclosure Rating | NEMA 4X (IP66) |
| Weight | 8.8 oz (250 g) |
| Compliance | BTL, CE |
Documentation
Frequently Asked Questions
What does '3-in-1' mean on the Digihelic DHC?
It combines three instruments in one: a digital display gage, two SPDT control-relay switches, and a transmitter with 4-20 mA and selectable voltage outputs.
Can it measure velocity and flow, not just pressure?
Yes. The DHC operates in pressure, velocity, or volumetric flow mode and reads in several selectable engineering units; velocity and flow modes use a configurable K-factor and duct area.
What communication protocols does it support?
Selectable BACnet MS/TP or Modbus RTU over RS-485, with baud rates from 9600 to 115200.
Can it be calibrated in the field?
Yes. Menu-driven zero and span calibration lets you maintain accuracy in the field without returning the unit.
- Series:
- Series DHC Digihelic
- Product Type:
- Differential Pressure Controller
- Pressure Type:
- Differential
- Pressure Range:
- 0-0.25 in w.c.
- Range Type:
- Unidirectional
- Accuracy:
- 1.5% FSO
- Output Signal:
- 4-20 mA + Selectable Voltage
- Communications:
- BACnet MS/TP or Modbus RTU
- Display:
- Backlit LCD with LED Setpoint Indicators
- Enclosure Rating:
- NEMA 4X (IP66)
