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.

 

 

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)
Registers	Data Type	Data Size	Purpose
0x0006,0x0007	Float	2 registers	Requests 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)
Registers	Data Type	Data Size	Purpose
0x1000	Integer	1 register	Changes 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 Pin	Wire Color	T-Node FR Signal
1	Green	RS485A
2	Blue	RS485B
3	Brown	Pass-through
4	Red	12VDC
5	White	Pass-through
6	Yellow	Pass-through
7	Black	GND
8	Orange	Pass-through

 

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).

 

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.

 

Maintenance

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.