10 Facts About the Geiger Counter Functionality, aka RFID Tag Locator

1. What is a Geiger Counter?

When first developed in 1928, the Geiger Counter, also known as the Geiger-Muller Counter, “was an instrument used for detecting and measuring ionizing radiation” in the physics and nuclear industries. 1

The basic purpose of a Geiger Counter is to detect the presence of a desired object or substance. Geiger Counters use a ticking noise to indicate the proximity (or level of concentration) of a desired object. The frequency of the ticking noise increases as the Geiger Counter becomes closer to the object (or the concentration increases).

The same basic Geiger Counter principle has been applied to detecting RF energy and incorporated into  mobile RFID readers to locate specific RFID tags. Because the Geiger Counter feature is used to detect RF energy and has a similar purpose and ticking noise as the original Geiger-Muller Counter, the feature was named after the original.

2. What does it do?

Geiger Counter functionality on RFID readers allows users to determine the location of a specific  RFID tag within a certain range. Most RFID readers with Geiger Counter functionality allow the user to type in, paste in, or click on a specific RFID tag’s EPC number. Once the Geiger Counter feature is on and the specific RFID tag is in range, the reader will beep louder and faster the closer it gets to that specific tag.

3. Do all RFID readers have a tag locator feature?

While many mobile RFID readers ship with a demo Tag Locator (i.e. Geiger Counter) application or have a demo version available for download in an app store, not all do. For readers without a demo Geiger Counter program, a software developer could write an application to create the program using the manufacturer’s API ( Application Programming Interface). Fixed RFID readers generally do not ship with this feature due to their mobility constraints.However, it is possible to create a Tag Locator application using a fixed RFID reader (and other necessary products) on a mobile cart powered by batteries.

4. Which handheld/mobile RFID readers have this feature?

RFID is gaining in popularity, and the market for handheld/mobile RFID readers is continually evolving. The chart below lists the top handheld/mobile RFID readers on the market (as of the publish date of this article), as well as information about their RFID tag locator features.


RFID Readers

Geiger Counter/ Tag Locator

Technology Solutions Ltd. (TSL)

TSL 112811531166

Yes, via compatible apps - RFID Explorer & RFID Tag Finder

Turck (U Grok It) 

UHF Reader for Smartphones (Grokker)

Yes, via compatible apps - Turck RFID, Send Grok, Discover Grok.

Zebra Technologies


Yes, via compatible apps for the RFD8500, and on the device for the non-sled RFID readers

Smart Label Solutions (SLS)


Yes, via compatible apps - smartEIT, smartVIEW

5. How is the RFID tag located?

Although a Geiger Counter feature can be implemented and set up in a few different ways, the software is usually programmed to find and read a specific  tag’s RSSI in combination with either reads per second or output power (depending on the manufacturer). As the signal gets stronger and/or the number of reads/second increases, the program tells the device’s audible sound to beep at an increasing rate. Some programs also use the same data to display a graphic that increases or decreases, depending on proximity to the tag being located.

6. Does the functionality of the Geiger Counter have limitations?

The Geiger Counter feature is mainly limited by the location of the tagged item. If the tagged item is out of the read range, the RFID reader will not be able to find it. Additionally, because many factors affect RFID read range, locating specific RFID tags with exact precision may not always be possible. Depending on the system setup and the surrounding  environment, the precision may vary from inches to several feet.

7. What is the maximum distance from which I can find an RFID tag when using the Geiger Counter Feature?

The maximum distance typically depends on the maximum read range of both the RFID tag and the RFID reader. When calculating the read distance, it is recommended to take the tag’s read range and the RFID reader’s read range, then use the lesser of the two to determine the possible read range.

For instance, the  Smartrac Dogbone has an average read range of around 15-20 feet, whereas the Alien SIT has an average read range of around six inches. At the highest transmit power, the TSL 1128 can read certain tags from around 23 feet away. The Smartrac Dogbone can be read from about 20 feet away, whereas the Alien SIT can be read starting around 6 inches away.

8. Can the read distance be controlled?

With most handheld RFID readers’ Tag Locator feature, the read distance can be adjusted by modifying the reader’s transmit power.

When you are looking for a tagged item in a large area, a higher  transmit power is recommended so that the tag can be located from a greater distance. However, if a tagged item is located in a smaller area, such as a densely packed file shelf, a lower transmit power is often recommended so that the RFID tag can be more precisely located within the small section.

9. How accurate is the Geiger Counter Feature?

Any Geiger Counter feature can direct a user towards an RFID tagged item or at least point the user in the right direction, depending on how far away the RFID tag is. Due to potential issues with  multipath and RF interference, precisely locating an RFID tag might not always be possible. To increase precision, reference questions 7 and 8.

10. Which RFID applications use this feature?

RFID applications that typically use the built-in Geiger Counter feature, or a similar custom feature, typically include applications that track and locate specific items.

●  File Tracking

●  Asset Tracking

●  IT Asset Tracking

●  Inventory Management


Do you have any interesting facts about the Geiger Counter feature available on mobile RFID readers? Tell us about it in the comments below - we would love to feature your first-hand information! For more information about all things RFID - comment below or  contact us.

Read more about RFID reader features below:

1 -  https://en.wikipedia.org/wiki/Geiger_counter

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