TM 11-6625-3060-10
PRINCIPLES OF OPERATION
Downrange (u) and Uprange(t) Displays
When the RF PROBE signal level is below the range of the mV pushbutton selected the digital display will blank and a
downrange (u) display will appear. When the RF PROBE signal level is above the range of the mV pushbutton
selected the digital display will blank and an uprange (t) display will appear.
RF Millivoltmeter Display
A 4-digit light emitting diode (LED) display provides the rf millivoltmeter voltage measurement. The voltage range of
the display is selected by the FULL SCALE mV pushbutton switches (1, 3, 10, 30, 100, 300, 1000 and 3000 mV
ranges). A decimal point can be displayed with three least significant digits.
Limited Use of dBm Meter and Polarity (-)(Indicator.
a.
Power level measuring circuits (dBm) have not been incorporated in the ME-526AIUSM. The dBm meter
and the polarity (-) indicator operate and can be used for reference purposes. The dBm meter indicates relative signal
strength In the FULL SCALE mV range selected. The down scale of the dBm meter (ZERO at the bottom of the
scale) indicates a relatively low level input signal (for the scale selected). When switched to the lowest FULL SCALE
mV range it is used to adjust the zero of the M E-526A/USM. As the dBm meter reading increases toward the top of
the scale, the maximum for the range selected is approached. This is the point where the mV range switch must be
increased. When the dBm reading approaches the bottom of the scale the mV range must be decreased.
The negative (-) sign at the left of the digital display would be used to indicate the power level of the signal
b.
under measurement should the dBm feature be installed in the ME-526A/USM. The negative ( -) sign would be
displayed when the indicator displays a power level below 1 milliwatt (0.0 dBm). When the negative sign Is not present
the indicator would display a power of 0.0 dBm or higher. Therefore, as the ME-526A/USM is used when the negative
(-) sign just disappears, while adjusting the ZERO control with zero signal input, the sensitivity of the ME-526A/USM is
set for zero with zero signal input. When the dBm feature is not installed and the ME-526A/USM is displaying only mV,
the negative (-) sign indicates a negative zero offset when the input signal is zero. The ZERO control is adjusted so
that the negative (-) sign just disappears.
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