NexSens T-Node FR thermistor strings offer quick temperature profiles

By on July 3, 2013
NexSens Technology T-Node FR thermistor strings

NexSens Technology T-Node FR thermistor strings

NexSens Technology’s new T-Node FR thermistor strings have quicker warm-up times, reduced power consumption and titanium thermistors. The enhancements reinforce an already solid line of temperature strings.

Thermistor chains are usually made of long, one-piece cables containing multiple sensors that measure temperature (the thermistors themselves). By putting thermistors in a series, it’s possible to get a more complete temperature profile of a water body.

Because those models of thermistor string are difficult to service, NexSens’ T-Node FR thermistors and cables are assembled as individual parts in each string. This means maintenance is simplified and cable lengths between nodes can be shortened or lengthened as project needs change.

The new model has a warm-up time 10 seconds quicker than the previous model, which applies across a typical string of about 15 to 20 nodes. The reading time for each node is only two seconds, but the improved warm-up time leaves an opening for additional sensors to report parameters to data loggers within user-defined intervals.

One of the most significant enhancements is its reduced power consumption specs. Each node of the older model T-Node used 9 milliamps, whereas the T-Node FR uses a low of 0.5 milliamps per node when in sleep mode.

“The benefit of the new model is power consumption,” said Daniel Chai, product manager. “Now the new version has two modes: sleep and active. This will be controlled by the T-Node automatically, so you don’t need to set it.”

When in active mode, each node will use 1.5 milliamps of power, far less than the 9 needed before. The T-Node FRs will stay in active mode for about a minute before switching to sleep, unless they receive a command from a data logger, such as the NexSens iSIC.

Unlike the previous model, the new T-Node FRs don’t require any calibration. They also feature titanium thermistors, which can more easily detect the temperature of surrounding water. The titanium is robust, anti-corrosive and makes direct contact with water, giving a more accurate reading.

The titanium thermistor is an external improvement which couples with those made in the design and manufacturing process. The new T-Node FR’s circuit board is all new and features a more efficient microprocessor and firmware upgrade. The board is surrounded within the node by a more durable epoxy.

“It has a thinner consistency that lets it expand around the inner workings of the node,” said Steve Holderman, manufacturing manager.

Maintenance requirements are minimal for the T-Node FR. Firmware should be kept updated, o-rings may need a periodic re-greasing and customers may want to occasionally re-mount the nodes to mooring lines to keep them securely in place.

To replace one, the new T-Node FR simply needs to be assigned the same Modbus address of the one being removed. Each T-Node FR communicates through Modbus RS485, which lets the strings easily interface with industry-standard data loggers.

“Just remember what the address is in the temp string,” said Chai. “Assign the address and plug it in.”

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