The Use and Calibration of the Kern ME5000 Mekometer - SLAC ...

2.1.2. Short Distance Mode
.
ME5000 Data Reductions
For all distances below 20 m only two frequencies are found. For distances below about 8 m only one
frequency is found, and an approximate distance is required in order to resolve the distance.
Where two frequencies have been found the procedure is similar to that for normal range, (5-8).
DF = F2 - F1 (5)
Ni
Ni Cstp
Di = 2F. +ADC
I
D
Dl+&
=-
2
For the shortest distances, where only one frequency is found, an approximate distance is required,
(9-l 1).
?L =cs’p
2F1
N1 = md(D”“iADC)
05)
x = wavelength for frequency F1 (9)
D am = approximate distance
.- D = hNlsADC (11)
2.2. Atmospheric Corrections
After computing the raw distance afresh from the frequencies, the first reductions applied are three
different atmospheric corrections.
23.1. Refractive Index
The distance displayed on the ME5000 and recorded in the raw data file is calculated assuming a
standard atmosphere, Table 1.
TABLE I. Standard Atmosphere
The actual meteorological parameters are measured at both ends of the line and stored in the raw data
file in the following units:
Temperature: dry bulb temperature in Oc.
Moisture: relative humidity (%) or wet bulb temperature PC).
Pressure: in mmHg or mbar.
The atmospheric corrections are applied using the mean values for each of these parameters.
28
(8)
(10)