“How far?” – The impossible question

How far can a wireless logger be from its base station? It all depends on what's inbetween.

Up to 100m line of sight

When they talk about distance with wireless systems, they talk about “line of sight”. 

What this basically means is that if you used the system in an empty field, in the middle of nowhere, with no trees or hills, how far would the signal be able to go?

This is a good indicator for comparing systems. If you have a device that can go “50m line of sight” and “100m line of sight” then you expect the second system to be able to go further, and generally that should be true.

BUT it really is only good for comparing two systems. The actual distance is meaningless.

You aren't in an empty field

Most of our customers aren’t in an empty field. As soon as you have walls, doors, cupboards, people, etc, etc, etc then they block part or all of the signal.

Metal is by far the worst. Wireless signals can’t get through metal. When it comes to fridges and freezers which are metal structures, the only reason why wireless systems can work is because of the seal. This is the “hole” through which a wireless signal can get in and out. BUT it comes at  a cost, and the range of the wireless device is significantly reduced.

Is there a "rule of thumb"?

If you are monitoring a fridge (e.g. a vaccine fridge or commercial fridge) then the wireless temperature logger should be able to communicate to a base station in the same room or adjacent room. 

In a warehouse, a base station within the warehouse should be able to monitor the entire warehouse. The base station in an adjacent office is questionable.

Coolrooms  require the base station to be in the room the coolroom opens into, or possibly the adjacent room. If, however, there is a freezer that is accessed through the coolroom then the signal is unlikely to get out. An external probe is your best option.

Is there a simple check?

For rooms, coolrooms, etc a simple test is to check your mobile phone to see if you have mobile coverage or wi-fi. If you don’t have either, then it is likely to be a problem.


What can be done if the signal isn't strong enough?

There are a number of things that can be done to try and improve the range:

Reposition the base station and logger

Ensure that the base station and logger are not against metal, or surrounded by something that is likely to block the signal.

Moving the base station so that it is higher and clear of everything else tends to improve the range.

Hanging the logger from a shelf, towards the front of the fridge, will increase the range. 

Water (and ice) also has a major impact on range. Having the logger behind liquids or stock will also have a negative impact.

Move the base station

The base station needs to be plugged into an ethernet port, and this tends to be a limiting factor as to where it can be placed.

There are devices available that convert from wi-fi back to ethernet. If you have wi-fi near the loggers then you can use one of these to place the base station in the same room. These devices are typically $50 to $100. You may want to add this to the budget of the job.

Extenal probe

An external probe means that the actual temperature sensor can be in a different location to the electronics. Placing the electronics outside the fridge and the sensor inside means that you have overcome the biggest issue.

It does, however, require a hole for the probe to pass through. This may mean that you need a tradesperson to install it for you, or it may impact on the warranty.

Some people will also try to place a probe in a fridge and run the cable past the seal. This is not an ideal solution. In some cases it has resulted in excessive condensation in the fridge, especially in humid areas.

Not all wireless systems are the same

A complicating factor when comparing distances is that not all wireless systems are the same.

Different frequencies act differently. Currently there are 3 common frequencies in use in Australia – 433MHz, 915MHz, and 2.4GHz.  (MHz is “mega hertz” and GHz is “giga hertz”).

433MHz is old technology, 915MHz was more recent, and 2.4GHz is where all the modern action is happening, though ironically the old technology had better performance than the newer frequency.

We are also experimenting with a new technology that has a range of over “1km line of sight”. If we can’t get this system working on your site, then the new system may be an option.

What if it just doesn't work?

We are here to help you successfully install a system that does what you require. 

We can discuss the site with you beforehand to advise on the expected number of base stations and their range. Call us on 1300 30 33 34.

We provide full support during the installation and afterwards. Just email or call. 

We can swap loggers with ones with external probes to see what happens.

We may recommend getting a wi-fi range extender (for the extra ethernet port). It is your decision if you want to spend the extra money to make the system work.

Ultimately, we can’t guarantee that the system will work on all sites, for all fridges etc.

There are some jobs that we will warn you that it isn’t the best solution before you place an order. We have alternative systems and one of these may be a better solution. In some cases we will actually recommend that you go with a more expensive system from another supplier, or use a cabled solution, or just say it is impossible. 

There are some jobs where we just couldn’t get them to work. We have tried as many of the options that you are happy with, and we just can’t get it to work. In this case we will refund either the part that isn’t working, or the entire system. It’s up to you.

The one thing that we do ask, however, is that on larger installs you use one logger to test all locations before you complete the installation. If we can avoid using all the loggers before discovering the problem it would be appreciated.


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