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TL-300 Borehole Temperature Logger

TL-300 Borehole Temperature Logger
TL-300 Temperature Logger

  • 300 Stations over 600'
  • .1C resolution
  • Records all sensors in less than one second
  • Provides a continuous temperature profile
  • Remains stationary in well
  • Unattended operation

TL-300 Specifications




  • Sanitary seal detection

  • Inflow / Outflow analysis

  • Crosswell Flow

  • Production Aquifer Choice

  • Hydrological Research

The TL-300 is a portable, high resolution, multisensored temperature measurement system designed to aid in the investigation of new and existing water wells. The system consists of a weatherproof, lightweight data logger and an active, multisensored cable assembly. With up to 300 sensors downhole and a resolution of .1, the TL-300 provides a detailed and essentially continuous temperature profile of a well. This capability adds a new dimension to temperature logging and greatly increases the usefulness of this parameter as a logging tool.




The battery powered TL-300 is easily hand carried to the well site where data may be collected with or without operator intervention, and it may be left unattended to collect data over long periods of time. Once data has been collected, it may be transferred to an IBM-compatible computer for storage and further analysis with the Seistronix Temperature Utility program . The data may also be transferred to other programs for additional analysis.

The TL-300 is easy to set up and operate. Options are selected through a series of menus displayed on a large Liquid Crystal Display (LCD), and help is available at any point by pressing the <HELP> key. For many situations the set up simply involves specifying the depth of the cable.

Once the TL-300 is set up, data recording is initiated by pressing <START>. At this point, the instrument scans the sensors in the cable assembly, taking a reading (sample) from each sensor. This reading is stored in the TL-300's internal memory. Data recording will continue at the programmed sample rate (from every 5 seconds to once per hour) until <STOP> is pressed. The recorded data remains in memory even when the instrument is turned off. Up to eight different logging sessions may be stored in the TL-300 at one time.

During recording, the LCD screen shows a bar graph display of depth vs. temperature data for all (or selected) sensors downhole. After sampling is stopped, the stored temperature data can be played back on the screen at high speed, condensing the depth vs temperature changes that occurred over the recording interval (which might be 10 minutes, 10 hours or 10 days) into just a few seconds. This allows subtle changes in the temperature gradient and long term trends to be easily to detected.



The standard cable section is 120' long with small integrated circuit sensors molded into the cable every two feet (other sensor spacings are available). This cable is connected to a short lead-in cable which plugs into the data logger.

The cable is small enough to fit down a two inch diameter hole. Cable sections may be added to the TL-300 in the field. Up to five cable sections may be connected together for a total cable length of 600'. For deeper applications, a longer lead-in cable or a wider sensor spacing may be used.

The cable is jacketed in artificial rubber, is neutrally buoyant in water, remains flexible at low temperatures, and is not affected by most chemicals or sunlight.


The TL-300 has three major advantages over single sensor loggers, which can make make most borehole temperature logging operations easier, less expensive, and more accurate.

  1. Single sensor logging requires an operator at the hole for each logging run.
    With TL-300 the hole can be logged unattended over long periods of time with no operator intervention.

  2. In single sensor logging, the sensor must be moved up the hole, disturbing the temperature gradient in the hole.
    Once the the TL-300 is inserted into the well, it doesn't have to be moved.

  3. Because a single sensor logger requires minutes and often hours to log even a medium depth hole, the temperature may change dramatically at one end of the hole by the time the sensor reaches the other end. The TL-300 records data from all sensors (up to 300 sensors) in less than one second.



Gravel/Cement grout location
When the gravel/cement is poured or pumped into the annular space of a water well or monitoring well, there is always some question whether the materials are at the proper depths. The TL-300 system can eliminate the guesswork by continually monitoring the heat of hydration of the cement from before onset until the cement cools. Voids in the grout may also be detected in this manner.

In the adjacent example, the TL-300 was used to log a well two days after the sanitary seal was placed in the well. Each line in the TL-300 data set represents a temperature profile of the well taken at 30 minute intervals.

Even after waiting 48 hours to log the well, the bottom of the seal can be very clearly seen.

TL-300 Temperature profile of grouted well

Production Aquifer Choice
In many water wells, two or more aquifers are encountered during drilling. Assuming that there is a temperature differential between aquifers, the TL-300 system may be used during pump test to determine the most productive aquifer.


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