User Guide

The NexSens T-node FR Thermistor provides high precision temperature measurements. When multiple are assembled into a chain, the T-node FR can be used for temperature profiling in lakes, streams, and coastal waters. It features an integral titanium thermistor secured and epoxied in a protective housing for underwater deployments.

NexSens T-node FR Thermistor.



Sensor Information

  • Power Requirement: 5-24VDC
  • Protocol: Modbus-RTU
  • Baud Rate: 19200
  • Parity: N81
  • Default Address: 1*
  • Universal Address: 251
  • Format: Big Endian
  • Timeout: 500ms

*On a pre-assembled string with multiple nodes, the nodes will be addressed in increasing numerical order.


Modbus-RTU Register Information

Function 0x04 (Read input registers)
RegistersData TypeData SizePurpose
0x0006,0x0007Float2 registersRequests the temperature recorded by a T-node FR sensor in Celsius

Ex. 01, 04, 00, 06, 00, 02, 91, CA

  • Requests the temperature reading of a T-node FR sensor with Modbus address 1, reported in Celsius.


Function 0x10 (Write multiple registers)
RegistersData TypeData SizePurpose
0x1000Integer1 registerChanges the Modbus Address of the T-node FR sensor node

Ex. FB, 10, 10, 00, 00, 01, 02, 00, 05, 0D, 36

  • Changes a T-node FR node (at the universal Modbus address of 251) to a new address of 5.


CAUTION- Only connect a single T-Node FR at one time when sending the address change command, especially when the universal address ‘251’ is used.


UW-FLxR Cable Connection

The NexSens UW-Receptacle to Flying Lead cable is an accessory that may be purchased separately for integration of a T-node FR string with a third-party data logger or SCADA system. NexSens X2-series data loggers have built-in UW-receptacle ports to accommodate a direct connection of the string.


UW-FLxR Wiring Table

Receptacle PinWire ColorT-Node FR Signal


Pre-Deployment Check/Setup

It is recommended that field deployments be carefully planned, and it is best to completely configure the system on a lab bench and test it for a period of time prior to taking it to the field. This will ensure a successful deployment and quality data collection. Additionally, it is much easier to troubleshoot problems in the lab than in the field.


Connector Inspection

Whenever a string is assembled or re-connected, verify that the plug and receptacle O-rings of each sensor and UW-connector cable are present and in good condition. Additionally, verify that there are no signs of moisture or corrosion on any of the T-Node FR or UW-cable connectors (if re-deploying an old string).

Inspect the plug and receptacle O-rings on each T-Node FR thermistor as well as on all sensor cables comprising the string.


TS-Clamp mooring line connection

The TS-Clamp accessory can be used to affix a T-node FR thermistor string to a mooring line for deployment.

Cable Armoring

For any T-node FR deployment, apply cable armor to all portions of the sensor string that have the potential to wear against irregular surfaces.



There is very little maintenance required for T-Node FR temperature strings because they are designed for long-term deployments in submersible applications.

  • Cleaning
    • Any bio-fouling that accumulates on T-node FR temperature strings during deployments should be cleaned using a soft cloth or soft-bristled brush along with soap and water.
  • Calibration
    • T-Node FR thermistors are capable of holding their factory calibration indefinitely and do not require re-calibration.
  • Storage
    • T-Node FR thermistor strings should be stored in a cool, dry place.