How moisture affects the reading of sensor tags

[RFMicronRFMicron Ambassador ★★★★]

Moisture can affect the ease of reading a sensor tag. In the case of RFMicron’s moisture sensors, the tags are intended to detect small amounts of visible moisture — small droplets on the moisture-sensing area of the sensor (the area with the interleaved metal fingers).  Significant amounts of moisture on the antenna can reduce the read range of the sensor or make readings more difficult to capture.

[YAO JUNCommunity Member ★★★★]

Hi, could you tell me the detecting accuracy of this moisture sensor, for example, if the air moisture is 50%, what the data range will be readed from this moisture sensor? What is the moisture range could be detected by this sensor?  Thank you!

[Brian YoungRFMicron Team Member ★★★★]

The moisture sensors detect liquid water rather than water vapor, a gas,  so the sensor codes will not move based on changes in humidity.  The amount of liquid water detected depends on the sensor type and where the water touches the sensors.  For example, the RFM2110 can detect >0.05 ml of water for most areas of the sensor.

[MartinezCommunity Member ★★★★]

Hi bryan,

Are there any data sheets for 2100? I cant really see the moisture value showing up

[Brian YoungRFMicron Team Member ★★★★]

There is a brochure at http://rfmicron.com/rfm2100-wireless-flexible-moisture-sensor/ that shows sensor code movement for two different methods of exposing the sensor to water.  For simple testing, you should see very good code movement if you put 1/2 drop of water directly onto the interdigitated finger structure.

[MartinezCommunity Member ★★★★]

Thank you.

Ill try to re read this document. Im using

Thingmagic astra reader,but i can only see rssi values. Do you have any idea to pull off the moisture value?

[Brian YoungRFMicron Team Member ★★★★]

The details for reading sensor codes are in our app note “Reading Magnus-S Sensors Application Note”, and it can be downloaded from the “Tools and Training” area.  If you have not read this, then this is the best place to start.  There is sample ThingMagic code there.  If you have read this, then we’ll have to dig in a little more.

[MartinezCommunity Member ★★★★]

I have seen the file. Would like to ask then if the reader already produced a sensor code. Is there any document correlating this sensor code to moisture?

[Greg PitnerRFMicron Team Member ★★★★]

In general, the Sensor Code on the 2100 drops when water is on the interleaved finger structure on the tag. It’s not a calibrated measurement, in the sense of a certain volume of water being equal to a certain numerical change. But more water does tend to result in a larger change in the Sensor Code in comparison to when the tag is dry.

[MartinezCommunity Member ★★★★]

The example in the pdf only pertains

To tempwrature and not moisture

[Greg PitnerRFMicron Team Member ★★★★]

In the application note you want to look for material on the “Sensor Code”. This is the value that can be used to detect moisture. It’s not called the “Moisture Code” because, strictly speaking, it changes in response to de-tuning of the tag antenna. This can be caused by moisture, but not exclusively. So the Sensor Code can indicate different things, depending on the how the tag is designed and installed. I hope that helps.

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