What do these numbers mean on my Conserv Range Tester?

A range tester can help figure out why a sensor signal might not be reliable, if you know how to interpret the numbers

So you have a Conserv Range Tester to help you diagnose an intermittent readings issue, or to help plan. your installation.  Great!  It's a handy tool for figuring out just how far a signal can go, and how much obstructions like walls, cabinets or floors can affect range.  Here are a few tips on how to use it and how to read the numbers.  Radio frequency transmissions can get complicated, but there are some simple guidelines that can help you understand what is happening.

Getting it running.

To start, turn on the range tester close to one of your gateways.  This will ensure that the range tester can join up to Conserv's global network properly, which is essential for getting those range numbers to display.  You'll know it has joined when the display starts showing some numbers instead of just "N/A" for "Not Available".

The numbers.

The Conserv Range Tester, once connected, will show you two numbers; Received Signal Strength (RSSI), and Signal to Noise Ratio (SNR).  The range tester works by sending a signal to the gateway, which then responds with a signal of its own.  It is the return signal that we measure and display.  This is typically slightly weaker than the original signal transmitted, but that helps us ensure that we aren't reporting a false positive (that is, saying that a sensor will work in a location when it will not).

Received Signal Strength (RSSI)

RSSI is a measurement of the strength of the signal from the gateway to the range tester.  It is, essentially, how well the range tester can "hear" the gateway.  The RSSI value ranges from zero (which would be a perfect connection, and is never achieved in the real world) to -145 (a very weak signal).  These numbers are shown on the display as S:G or S:O or S:W, corresponding to Signal Good, Signal OK, or Signal Weak, along with the exact RSSI number from 0 to -145.  It is worth noting that even a weak signal can be reliably received, if there is little noise in the environment.  A good rule of thumb is to aim to get an RSSI above -125. We'll talk about noise next.

Signal to Noise Ratio (SNR)

SNR is a measurement of the ratio between the signal (the thing we want transmitted) and noise in the environment (other things happening on the same frequencies that we do not want).  Any ratio above zero means that the signal is stronger than any background noise.  Any ratio below zero means that the background noise is stronger than the signal.  As long as the SNR is above -8, it is possible to successfully separate the signal from the noise and receive the message.  These numbers are shown on the display as N:G, N:O, or N:B, corresponding to Noise Good, Noise OK, or Noise Bad, along with the exact SNR number from 10 to -8.  A good rule of thumb is to aim for a number greater than -8. Noise can come from other things using the same frequencies (such as wireless security systems or phones) or from mechanical or electrical equipment.

Conclusion

Figuring out the range of a wireless device can be complicated, as it involves understanding the building, what is in it, the relative locations of all of the sensor equipment and what else might be around that creates interference.  With a range tester and a little knowledge, it becomes a little easier!