Bird Technologies VPM3 - Manual (Page 55)

47
Terminating Power Sensor (TPS)
Description
The Bird Terminating Power Sensor (TPS) and 5015-EF extended frequency TPS
are a diode-based power sensors that measures true average power.
For best results, wait 5 minutes after applying power to the sensor before taking
readings.
Zeroing Sensor
Over time, the sensor’s “zero value” (reading with no applied RF power) can
drift, making all readings inaccurate by this value. For example, if the zero value
is –0.02
W, measuring a 50 W signal will give a reading of 49.98 W, a 0.04%
error. Measuring a 1 W signal will give a reading of 0.98 W, a 2% error. If the
drift would be a significant error, rezero the sensor:
1.
Ensure the sensor has reached a stable operating temperature.
2. Ensure no RF power is applied to the sensor.
3. Press “Zero” to begin Calibration.
Note:
Calibration will take about 40 seconds. Do not interrupt the
calibration! A bar on the screen will display calibration progress.
Correction Factors
The Bird TPS-EF uses frequency-dependent correction factors to improve its
accuracy. To use the correction factors:
1.
Look at the Correction Factor Table on the side of the TPS and find the correc-
tion factor corresponding to the frequency under test.
2. Add the correction factor to all other necessary offsets (for example, the
coupling factor of a directional coupler).
3. Enter the total offset into the power meter.
4. Input the Offset on the VPM3. See “Input Offset” on page 18.
Note:
Correction factors are only required above 4 GHz. Below
4 GHz, the TPS-EF can be used as a normal TPS. See “Terminating
Power Sensor (TPS)” on page
47.