Borehole Logging

Mini VLQ now available

New Mini VLQ needle probe for thermal conductivity meter TK04The new Mini VLQ is a 50 mm long needle probe with a diameter of 2 mm for small samples. It can be used where standard size probes are too large for the available sample dimensions. This includes compressible materials like soil samples which cannot be tested with the already available Mini HLQ for plane surfaces.

Use the Mini VLQ for samples with a minimum diameter of 40 mm and a minimum length of 60 mm. The Mini VLQ has a measuring range of 0.3 to 6 W/mK and an accuracy of ± 5%.

 

New Mini VLQ   ˅

Temperature Logging in Boreholes

After positioning a sensor cable in the borehole, registering a complete temperature log only requires a single measuring cycle. Before starting measurements, a short waiting time of about 15 minutes is sufficient to let the disturbances of the temperature field cease which are caused by inserting the sensor cable. As this method is significantly faster than usual temperature data loggers, you can record several logs in short intervals in order to detect disturbances and to improve reliability by calculating average temperature values over various measuring cycles. As the TkMonitor system is able to operate unattended, long-term changes in temperature distribution can be monitored automatically in intervals freely chosen by the user.

Example measuring layout for temperature logging in boreholesMeasuring Layouts

For a basic measuring layout just insert a sensor cable of sufficient length and suitable sensor spacings into the borehole and connect it to the TkMonitor temperature recorder, either directly or through an extension cable (view photo). Cables configured individually, e.g. with smaller sensor spacings in certain depths, are available on request.

Even using standard cables (sensor spacing 1 or 2 m), effective sensor spacing can be reduced considerably: either shift a single cable downwards by a short distance after each measuring cycle, or use several standard cables in parallel in the same borehole using suitable offsets. If sensor spacings should be reduced for certain depths only, short cables with small sensor spacings connected through an extension cable can be used in addition to a long standard cable. As sensor cable diameter is very small, nearly in all cases more than one cable will fit into the borehole.

Example borehole temperature logData Processing

Using the included TkMonitor software, the temperature data are transferred to a computer or notebook. The depth values of the sensors can be corrected to match any desired reference depth (e.g. when using extensions or several cables with different offsets). Just enter the distance between the zero sensor of a cable and the chosen reference depth, and the software will adapt the depth values of all sensors belonging to this cable automatically. For further processing, the complete temperature data or any individual selection of depth values and measuring cycles can be exported to a *.txt or *.csv file which can be opened by nearly any software application.

A typical measuring configuration for temperature logging in boreholes consists of just a single sensor cable connected to the TkMonitor temperature recorder and positioned in the borehole using a deflection roller.