Understanding how liquids inhibit RFID system communication is important. Check an actual experiment with RFID tags submerged in water.

If you have had contact with RFID technology you have probably heard about how liquids inhibit RFID systems.

However, no matter where you read, it is really hard to understand in an easy way what to expect of the impact from liquid environments.

No wonder, it’s not an easy reply. The real issue is that RFID communication depends on a number of factors, not just the liquids in the environment. We will prove this with a very simple test.

UHF RFID sensor tags underwater test

We develop a really simple set up for easy understanding of the results.

A small pot full of plain water, a sensor tag, a reader antenna and an RFID reader is all we needed.

We positioned the reader antenna on top of the pot so that we could have as much energy as possible in the area where the RFID tag would be – mainly inside the pot.

Liquids inhibit RFID - Test setup

Liquids inhibit RFID – Test setup

Initial round of tests

The tests were very simple:

  1. Read the tag outside the water
  2. Read the tag on top of the water
  3. Read the tag inside the water – around 5cm under water
  4. Read the tag inside the water – bottom of the pot (around 20cm under water)

We honestly expected the tag to lose communication fairly soon after being under water but we were glad to check that while 5 cm under water we still had good communication.

However, the funny part is that we lost communication as we moved down but we were able to read the tag when at the bottom of the pot without problem.

What would you say the reason was?

Changing the pot for a second round of tests

Well, it turns out that the metal pot was actually working as an antenna for the RFID tag – not a technical explanation at all by the way J.

We carried out the test with a plastic pot with the same setup and we got the same results except with the bottom of the pot test. With the plastic pot we could not read the sensor tag at all when the tag was in the bottom.

Liquids inhibit RFID system communication

So yes, liquids greatly inhibit RFID energy transfer and communication. There’s no denying that but it’s worth understanding that some setups can work – EVEN UNDERWATER AND WITHOUT USING CUSTOMIZED ANTENNAS.

The bad news is that it is very hard to guarantee what will work and what not. It’s all about testing different setups and checking what works best.