Durable Underwater Temperature Logger

Self-contained underwater temperature logger for long-term deployment. Reliable measurements, large memory size and replaceable long life battery.
Ideal for monitoring temperature in oceans, rivers and lakes. Can be easily attached to moorings, buoys and nets.

Key Features

  • Compact and durable water temperature logger
  • Long life replaceable battery
  • Large memory size
  • Fast response temperature sensor available
  • Easy to attach to underwater gear


Compact and durable

This robust mini water temperature logger is designed for long-term deployment and to withstand harsh conditions underwater up to 400 meters. A deepsea version in titanium housing is also available. The logger is durable with its robust and non-corrosive plastic housing, dimensions 130 mm x 25 mm.


The Starmon mini temperature logger is designed for use in underwater environments. Examples of applications:

  • Sea temperature logging for oceanographic studies
  • Temperature monitoring in rivers and lakes, ecosystem research
  • Attached to fishing gear for fisheries research, scientific and commercial
  • Mapping sea temperature at aquaculture sites

Long life replaceable battery

The battery typically has a long life of over 10 years. Actual lifetime depends on sampling interval used and frequency of use. The battery is replaceable.

Large memory

Memory size is 262,000 measurements (standard) but can optionally be increased to 524,250 measurements.

Fast response temperature sensor available

This logger is available with a fast response temperature probe. The time constant in the fast temperature response version is 2 seconds, compared to 18 seconds in the standard version. This is useful when measuring while sinking or towing gear.

Easy to attach to gear

The logger housing has holes for mounting to ocean moorings, buoys, nets, deployment lines etc. For more flexible mounting a stainless steel tube can be supplied, which fits around the logger.

Size (Diameter x Length)25mm x 130mm
Housing MaterialPlastic
Weight (in Air/in Water)170g/80g
Temperature Range-2°C to +40°C (28°F to 104°F)*
Temperature Resolution0.001°C (0.0018°F)
Temperature Accuracy+/-0.025°C (0.045°F)
Temperature Response TimeTime constant (67% of full value) is 18 sec. Option for fast response of 2 sec.
Pressure ToleranceMax. 400 m / 40 bar
Memory TypeNon-volatile EEPROM
Memory Capacity262,000 measurements (standard)
Memory Increase Option393,750 measurements or 524,250 measurements
Memory MangementCustom programming
Sampling IntervalUser specified in second(s) minute(s), or hour(s)
Minimum Measuring Interval1 second
Multiple Intervals OptionUp to 2 different intervals
Data Retention25 years
ClockReal time clock. Accuracy +/-1 min/month.
Communications9 pin RS-232C serial cable w/USB serial converter.
Attachment Hole2.8 mm (diameter)
Battery Life12 years**
Replaceable BatteryYes

*Outside ranges available upon request.
** For a sampling interval of 2 minutes.
Warranty: 12 months.

Simple in Use, From Setup to Data Retrieval

The data logger and the accompanying items are designed for ease of use throughout the research process, from setting up the logger, attaching it, to retrieving and analysing the data. The logger is supported by the SeaStar software and the PC communication cable which have to be purchased with the first order.

Setting up the Logger

To launch the temperature data logger for measuring, the end cap of the housing is unscrewed and a USB cable connects directly to a PC computer. In the SeaStar software, the user sets the start time, start date and sampling interval before starting the logger in measurement mode. The logger synchronizes its internal clock with the date & time on the computer being used.

Memory and Battery Life Calculations

The software automatically calculates when memory fills based on certain interval settings, making it easier for the user to decide how to program the tag. Estimation on battery consumption during that time period is also calculated. It is also possible to have the software do memory and battery calculations for a specific measuring period.

Uploading the Data

After recovering the logger, it is connected with the communication cable to the PC and the recorded data is uploaded to the software. The results are displayed both in graphic and tabular form and the data can be exported to other programs. The time series data shows each measurement with its own time stamp.

Low energy consumption

After data retrieval the logger can be restarted or put into sleep mode for later use. Battery life estimation is always reported upon connection with the logger. Due to the low energy consumption circuitry design the battery life is long, but the actual lifetime depends on usage and sampling interval used.