Campbell TDR100 Instrukcja Obsługi Pobierz pdf (Strona 25)

TDR100

6.2 Discussion of TDR Instruction Parameters (Instruction 119)

6.2.1 Parameter 1: SDM Address

The SDM address of the TDR100 is set by selecting hexadecimal values with

the thumbwheel switch on the TDR100 front panel. Instruction 119 requires a

2 digit integer that is the base 4 value of the TDR100 address. See Table 5-1

6.2.2 Parameter 2: Output Option

6.2.2.1 Enter 0: Measure La/L

In the section on TDR Principles, the equation

is presented. The terms of this equality can be related to volumetric water

content using empirical relationships such as equations [3] and [4] shown in

Section 7. The apparent length of the probe rods, L

, changes with water

content. Dividing L

by the real rod length, L, gives the square root of

dielectric constant. The L

/L value is empirically related to volumetric water

content using calibration functions of the form θ

= f(L

/L). See Section 7 for

commonly used calibration functions.

6.2.2.2 Enter 1: Collect Waveform

The digitized reflection waveform can be collected from the TDR100 by the

datalogger in ASCII format. Datalogger input storage must be manually

allocated for the waveform data points using “block allocation” in Edlog

datalogger software. The waveform is collected as an array. The first 9 cells

of the array is a header and contain values entered in Instruction 119.

Waveform values fill the rest of the array. Always allocate 9 more cells in

datalogger input storage than the number of datapoints chosen in parameter 6.

See Section 6.2.11.1 for header information.

6.2.2.3 Enter 2: Collect Waveform and First Derivative

The reflection waveform and the first derivative are written to datalogger input

storage. Input storage must be manually allocated. See Section 6.2.6. The

required number of input locations is twice the number of points (instruction

Instruction 119, parameter 6) plus 9 for the header information.

6.2.2.4 Enter 3: Measure Bulk Electrical Conductivity

The electrical conductivity routine in the datalogger returns the value

−

which must be multiplied by the probe constant, K

, to get an electrical

conductivity value. Kp is entered in Instruction 119 parameter 12. See

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