LBXXXA Series USB Powe
™
Product Manual PMA (Power Meter Application)
Revision: 08/02/11
- 23 -
This helped to stabilize the measurements. However, you have to wait several seconds between updates. Now try
connecting and disconnecting the RF source. You will see that each reading is independent of the previous reading
–
so that when power is disconnected the meter responds appropriately. You just have to wait a few seconds between
measurements.
We will take a different approach next. We will combine averaging with extended averaging. Extended averaging uses
exponential averaging in addition to normal averaging. This provides frequent updates and more stable readings. To
start we will set the averaging down to 2000
Averaging = 2000
Now setup extended averaging. To do this, click the arrow next to the extended averaging icon on the toolbar as
shown below. A drop down menu will appear. Select
Set Extended Averaging
. When the dialog box appears perform
the following:
Enable Extended Averaging = check box
Averages = enter 500
Click the OK button
After just a few measurements you should see the readings stabilize dramatically. This is what we wanted. Now we
can try a few experiments: Disconnect the sensor from the source (remove the incoming RF signal). Instead of seeing
a sharp decrease in power as we did with averaging set to 10000, the indicated power will drift downward slowly. This
is because the extended averaging is a “running” average of the past several readings. If you were not aware of this
fact this could be a very disconcerting result. Remember, we set the number of extended averages to 500 so the
readings now reflect the effects of the last 500 readings.
Given the current settings we might have to wait 10 minutes for a reasonable result. The most immediate action we
can take to resolve this action is to click the
Rst Max & XAvg
button on the front panel as shown above. When you do
this the reading should show that you have no signal connected. Try it now by clicking the
Rst Max & XAvg
button.
