Boonton 4240 RF Power Meter - Manual (Page 48)

Boonton 4240 Series RF Power Meter
these figures show the decay of measured power after a large signal has been applied. The typical error that can be expected
by zeroing too quickly after application of a large signal is equal to the offset power at the time of zeroing.
The Model 4240 initiates zeroing when the ZERO command is invoked. The user must delay zeroing according to system
requirements when the sensors are used over a wide dynamic range. For example, if it is determined from the application that
five seconds are required from power off to the zeroing operation, then the user should wait five seconds after removing
power from the sensor before executing the zero command.
The zeroing time on each range has been optimized for speed and accuracy. Total zeroing time is approximately 20 seconds.
Zeroing should be done when the instrument is turned on, the sensor has been changed, or the instrument has drifted a
significant amount with respect to the signal being measured. For large signals (range 4, 5, or 6), this may be once every
several hours, if at all. For very small signals (range 0, 1, 2, or 3), for optimum results, zeroing be done immediately before
each measurement.
Figure 4-1. 14-Point Sensor Calibration
Operation
4-2