CP480 Wireless Communication and Networks
Comparing Meters
In order for collected data to have any value, they have to be
independent of the specific instrument used. The purpose of this lab
exercise is to see how consistent different meters are.
Related to that is the meaning of signal strength indications on
wireless devices. (Often these are given as a percentage, or
indicated visually by a number of bars.) In this exercise you'll
determine how these indicators relate to actual power measurements.
Objectives
- To determine how consistent different meters are for the
measurement of power in wireless
systems.
- To determine a correlation between signal strength
indicated on a wireless device (such as a laptop) and actual
measured
power.
Equipment
- 2 wireless power meters
- laptop or other wi-fi device
You can use a smart phone if it has a wifi
connection with a power indicator.
Procedure
Comparing meters
- At the same point in the hallway, take a set of 10
measurements with each meter at their proper orientations for
maximum sensitivity.
- Average the readings as before, and see if the averages agree
within their experimental uncertainties or not.
- If they don't agree, try to figure out if there is something
you should be doing differently, and try it and see if you are
right.
Wireless device signal indicators
-
In order to get meaningful results, you'll need to start
by determining the directionality of the wireless device
antenna, just like for the power meter.
Do this, and note how the device should be oriented towards the
source for maximum sensitivity.
- If power is indicated by a number of bars
With one of the meters and your wireless device, move
along
the hall and record power readings at the transition point
between
different numbers of bars (e.g. 5-4, 4-3, etc.)
- If power is indicated by a percentage
With one of the meters and your wireless device, move
along
the hall and record power readings at 90%, 80%, etc.
-
Plot your results on a graph, and extrapolate to determine what
power is represented by full bars or 100%.
Are the indicators linear? logarithmic?
Before you leave the lab, have the lab instructor
sign your lab notebook immediately after your last entry.