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

4.1.4. Characteristic curve
ME5000 Test Measurements
The characteristic curve is the plot of signal output versus frequency over the range of the modulator
(460 - 510 MHz). This is the curve that is measured by the ME5000 when a modulator calibration is
performed. MEK’IEST performs a similar measurement but under its own control and with a smaller
interval. The output of the modulator is measured from 460 - 510 MHz in steps of 0.25 MHz, a total of
201 measurements. The modulator output is obtained in hexadecimal (range 00 - FF) and converted to
decimal (range 0 - 255). Figure 3 shows the characteristic curve and the bandwidth limits for the SLAC
instrument.
CHARACTERISTIC CURVE
06-30-1992 11:40:09
Freq. Hex Dee
460.00 15 21
460.25 17 23
460.50 19 25
460.75 1B 27
461.00 1F 31
461.25 21 33
461.50 23 35
461.75 26 38
462.00 28 40
. : :
: : :
Characteristic Curve - SLAC t/n 357089
0 I I
4to 470 480 490 503 510
4.2. Determining the ME5000 Windows
FraquonyOAHz)
FIGURE 3. Charactetistic Curve for the SLAC instrument
‘Ihe Kern specification for the ME5000 Mekometer quotes a minimum distance of 20 m. This limit is
chosen because every distance above 20m can be measured unambiguously with no help from the
operator. However, the Mekometer can measure shorter distances with special software and some
operator assistance.
The working range of the crystal that generates the modulation frequency is 460 - 510 MHz, but for
the measurement program supplied with the instrument Kern uses only the optimum portion of this
bandwith, viz 470 - 490 MHz. A distance can be measured unambiguously if two minima occur within
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