4-46
888-2586-001
9/15/06
WARNING: Disconnect primary power prior to servicing.
Platinum Z16HD+
Section 4 Overall System Theory
which controls the APC loop discussed earlier in this section. The correct APC_REF
voltage for a specific DAC_APC_REF number can be calculated from the formula:
APC_REF voltage = DAC_APC_REF * 0.004803
Example: For the nominal DAC_APC_REF value of 660, APC_REF Voltage = 660 *
0.004803 = 3.17V ±0.1V and can be measured at TP8 on the Master Controller. This
DAC value is used to control transmitter power level for all conditions where the
Master Controller is operational and the APC Loop switch S1-10 is closed.
4.8.2.2
Forward Factor and A/D_FWD_PWR
The Forward Factor is a calibration factor that is calculated during forward power
calibration. To check the Forward Factor press [HOME, MORE, CONFIGURATION,
C, A, B]. All Z16HD+ transmitters are factory calibrated with a forward sample voltage
of 8.9Vdc at 100% TPO, as measured at TP9 on the Life Support Board. This sample
voltage is low pass filtered on the Master Controller and then A/D converted in the
micro for metering. This A/D value shows up as A/D_FWD_PWR [HOME, MORE,
CONFIGURATION C, B], which at 8.9V should be very close to 806 (the A/D
converter is 10 bit for 0 to 1024 range, but the input to the A/D is not actually 8.9V). By
setting the FWD PWR CAL screen to 7000W and calibrating we are telling the micro
that 806 represents 7000W. The micro now calculates the Forward Factor by dividing
the 7000W by the square of 806 or
Forward Factor = FWD PWR CAL (kW) / A/D_FWD_PWR
2
Forward Factor = 7000W / 806
2
= 0.010775 (rounded up)
The A/D FWD PWR reading must be squared to make the voltage from the coupler
linearly track the transmitter power output (Power is the square of the voltage).
The Forward Factor is now used for all forward power level settings. For example, to
set the Low power control to 01.00kW you would press the lower button. This
gradually lowers the transmitter power output by reducing the DAC_APC_REF and
therefore the APC_REF voltage and transmitter power. This in turn lowers forward
power sample and the A/D_FWD_PWR number which can be calculated at 1kW as:
A/D FWD PWR = SQRT(FWD PWR / Forward Factor)
A/D FWD PWR = SQRT(1kW / 0.010775) = 304
At an A/D FWD PWR reading of 304 the front panel Forward Power meter will read
01.00kW.
Summary of Contents for Platinum Z16HD+
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