Model GF-N1000-DI


GreenFlow GF Series


RS-485 BACnet/Modbus Insertion Mount Thermal Dispersion Airflow/

Temperature Measurement Device (ATMD) for Round Ducts

The GF-N1000-DI airflow/temperature measurement device is functionally the same as the GF-A1001-DI with the exception that the BAS connection is via RS-485 field selectable BACnet MS/TP or Modbus RTU. In addition to airflow and temperature capability, device status is also available via the network.

  • Hospital, laboratory and clean room ducts
  • Terminal boxes
  • Outdoor air intakes to fan coils
  • Makeup air ducts to air handlers
GF-N1000-DI Overview PDF



  • Built-in transmitter provides one RS-485 BACnet MS/TP or Modbus RTU network connection for airflow, equivalent velocity pressure and temperature
  • Thermal dispersion technology
  • Calibrated between 0 and 3,000 FPM
  • Stable bead-in-glass thermistor sensors
  • NIST traceable airflow and temperature measurement
  • Calibrated to volumetric airflow standards
  • Accurate and repeatable
  • Field calibration is not required
  • Fits standard 4 to 16 inch round ducts
  • Easy to install insertion probe design
  • Available in aluminum or stainless steel


The GF-N1000-DI airflow/temperature measurement device is a low cost, high performance, solution for airflow and temperature measurement in smaller round ducts. The GF-N1000-DI is provided with an integral transmitter. Simply provide 24 VAC/DC power and connect the network connection to a BAS or other RS-485 device to determine the airflow rate and temperature.

The GF-N1000-DI airflow/temperature measurement device is designed for duct insertion applications. Probes are available with one or two sensor nodes. Installed airflow accuracy is ±4% of reading to NIST traceable standards when installed in accordance to published placement guidelines.

The GF-N1000-DI measurement device uses the principal of thermal dispersion to determine the airflow rate. Thermal dispersion is ideal for HVAC applications that typically require measurement of low air velocities. Each sensing node uses two thermistors to determine airflow. One thermistor is self-heated above ambient while a second thermistor determines the ambient air temperature. The power dissipated into the airstream is directly related to the airflow rate.

Each thermistor body is a hermetically sealed bead-in-glass probe. Bead-in-glass thermistors have demonstrated extreme stability and superior performance over chip type thermistors used by other manufacturers. The bead-in-glass sensor used has been time tested for over 35 years by GreenTrol’s sister company, EBTRON. Thermistors are potted in a waterproof sensor assembly and are designed for years of trouble-free operation.

Each sensing node is individually calibrated at 7 points in high-performance wind tunnels. The transmitter processes each individual sensor node independently. The result is the true average airflow rate and temperature when more than one sensing node is applied.


Airflow Measurement: Provides the average airflow rate in FPM [m/s] or CFM [LPS] via the network connection

Temperature Measurement: Provides the velocity weighted temperature in ⁰F [ ⁰C] via the network connection


Baud Rate, Protocol and Addressing: Set by DIP switch

End of Line Termination: Jumper

Important: Modification of the factory default settings requires that power is cycled to the device. It is recommended that each device is bench configured prior to installation OR settings are provided at the time of order so that the device can be factory configured prior to shipment.


Type: -DI Duct Insertion Thermal Dispersion Airflow and Temperature Measurement Probe

Available Configurations

4 inch [102 mm]: 1 probe x 1 sensor node

5 to 16 inch [127 to 406 mm]: 1 probe x 2 sensor nodes

Sensing Node Sensors

Self-heated sensor: Precision, hermetically sealed, bead-in-glass thermistor probe

Temperature sensor: Precision, hermetically sealed, bead-in-glass thermistor probe

Probe Tube

Material: Mill finish 6063 aluminum (optional: 316 SS)

Probe Mounting Brackets

Material: 304 stainless steel

Probe Mounting: Insertion

Sensing Node Housing

Material: Glass-filled Polypropylene

Sensor Potting Materials: Waterproof marine epoxy

Sensing Node Internal Wiring

Material: Kynar® coated copper

Airflow Measurement

Averaging Method: Independent, arithmetic average

Installed Accuracy: Better than ±4% of reading to NIST traceable airflow standards

Calibrated Range: 0 to 3,000 fpm [0 to 15.24 m/s]

Calibration Points: 7

Temperature Measurement

Averaging Method: Independent, velocity weighted

Accuracy: ±0.15⁰F [0.08 ⁰C]



Type: Non-isolated, field selectable MS/TP BACnet master or Modbus RTU connection (provide separate transformer to each GF-N1000-DI or an RS-485 network isolator if isolation is required)

B.A.S. Object/Register Read/Write Access: Yes

Device Load: 1/8 load

Supported Baud Rates: 9.6, 19.2, 38.4 and 76.8 kbaud


Environmental Limits

Temperature: -20 to 120 ⁰F [-28.9 to 48.9 ⁰C]

Humidity: 5 to 95%

Important: Not recommended for outdoor use

Power Requirement: 24 VAC (22.8 to 26.4 under load) @5V-A

Related Documents

Product Catalog
Data Sheets