Geodetic land survey leveling requires that correction of the instrument be done during the surveying process. This correction for sun, wind and air temperature is required to ensure accuracy of the leveling readings.

The thermistor is a dual sensor, miniature fan aspirated digital thermometer which displays the real air temperature. Mounted on the tripod, it has sensors to be located 0.3 m and 1.3m above ground level. Each sensor has a precision fan which draws air through a T shaped assembly, pulling air over a thermocouple. Using a Fluke dual input digital thermometer, both sensors display the actual air temperature at the survey location. The Fluke 54 II B meter logs both temperature readings in the meter. Those reading which are stored can then be exported from the meter using infrared data transfer, via a USB-A port on the side of the instrument.

The full explanation for the use and purpose of this instrument can be found on page 3-50, in the NOAA NOS NGS 3 "Geodetic Leveling" published by the National Geodetic Survey, Rockville, Maryland August 1981, Reprinted June 2001.

Web Link to NOAA NGS 3 Geodetic Leveling manuaL

To find more about the mission of the National Geodetic Survey branch of the National Oceanic and Atmospheric Administration, click here.

The case is constructed of heavy gauge welded aluminum, as are the two sensors. Manfrotto brand clamps attach the main case and sensors to your tripod making removal and setup easy.

The two, precision fans in each ‘T’ sensor are powered from the right side compartment, containing a standard lithium cellphone battery power bank that is recharged by a USB port on the bottom of the instrument, which is covered with a moisture-proof cap- no need to open the thermistor case to recharge the battery.

The battery pack provides over 7 hours of continuous run-time for fan operation.

A heavy duty, waterproof toggle switch is located on the control panel to turn fans on.

An analog voltmeter displays the battery voltage of 5 volts D.C. to power the (2) fans in the sensors.

Each T sensor thermocouple uses RF shielded cable which lessens the possibility of false readings from radio equipment and energy fields near the tripod location.

Using a dual thermocouple input Fluke model 54IIB digital thermometer which has the ability to log the temperature readings of both sensors at regular intervals. The stored readings are then transferred by infrared data transfer to output both thermocouple temperature reading sets. The temperature readings can be recorded in spreadsheet format on a laptop or personal computer by way of the USB-A port on the side of the instrument. A data collection application such as FlukeView is used to obtain the data. Please contact us for more information.

Regular, planned calibration checks are outlined in the National Geodetic Survey manual, outline the care of the instrument. The instrument should be checked in a controlled environment for correct temperature readings once weekly. The Fluke meter itself has adjustments for correcting minor thermocouple discrepancies and can be adjusted in the field, if so needed. The Fluke meter has a calibration certificate included and would need to be kept up to date, if so required by the end user, and is the responsibility of that end user for proper operation.

Main Instrument Housing Dimensions-

6.5 in. / 16.5 cm wide by 10 in. / 25.5 cm long

Total Unit Weight- 7.25 pounds / 3.8 kg