Method for temperature measurement

• US 9,212,954 B2
• Filed: 11/03/2010
• Issued: 12/15/2015
• Est. Priority Date: 11/05/2009
• Status: Active Grant

• Current Assignee: Teknologian tutkimuskeskus VTT Oy
• Original Assignee: Teknologian tutkimuskeskus VTT Oy
• Inventors: Lamy, Jerome, Sepp, Heikki
• Primary Examiner(s): Caputo, Lisa
• Assistant Examiner(s): Ahmed, Nasir U
• Application Number:
  US13/505,744
• Publication Number:
  US 20120275489A1
• Time in Patent Office: 1,868 Days
• US Class Current: 1/1
• CPC Class Codes: G01K 1/024 for remote indication
• CPC Class Codes: G01K 7/32 using change of resonant frequency of a crystal

Abstract

This document describes a method for measuring temperature. In accordance with the invention the temperature is determined from frequency variation of a local oscillator of a RFID tag (1).

Claims

1. A method for measuring temperature comprising the steps of:

performing a frequency variation of a single local oscillator of a RFID tag by varying a transmission timing sequence associated with the single oscillator of the RFID tag, the RFID tag having different timings;

measuring the frequency variation at the single local oscillator of the RFID tag by measuring a first backscattered frequency and a second backscattered frequency with respect to backscattered signals from the RFID tag using information of the single local oscillator in the RFID tag, wherein the second backscattered frequency is less than the first backscattered frequency;

determining an RFID tag ring oscillator frequency using the first backscattered frequency and the second backscattered frequency; and

determining an RFID tag temperature using, in part, a linear dependency of the RFID tag ring oscillator frequency.

2. A method in accordance with claim 1, wherein the frequency variation is determined by an RIM reader device by varying the reader preamble timing, in particular the duration of TRcal.

3. A method in accordance with claim 1, wherein the frequency variation is determined by an RFID reader device by varying the transmission timing sequence by using at least three different timing values during multiple transmissions.

4. A method in accordance with claim 1, wherein the determination of the frequency of the local oscillator is performed with the following sequence:

the reader issues a command requesting a response to the tag,

wherein the preamble of the command specifies the TRcal timing used by the tag to generate the backscattering frequency LF,

the tag measures the TRcal duration with its own oscillator clock,

wherein the TRcal is a discrete value in the tag logic,

the tag backscatters the response using the discrete LF value

TRcount=round(TRcal·

f_clk)

5. A method in accordance with claim 1, wherein temperature dependence of the tag is determined for a set of RFID-tags based on the manufacturer of the tag.

6. A method in accordance with claim 1, for precise measurement.

7. A method in accordance with claim 1, wherein calibration of tags is made for samples of manufactured tags.

8. A method for measuring temperature comprising the steps of:

performing a frequency variation of a single local oscillator of a RFID tag by varying a transmission timing sequence associated with the single oscillator of the RFID tag, the RFID tag having different timings;

measuring the frequency variation at the single local oscillator of the RFID tag by measuring a first backscattered frequency and a second backscattered frequency with respect to backscattered signals from the RFID tag using information of the single local oscillator in the RFID tag, wherein the second backscattered frequency is less than the first backscattered frequency;

determining an RFID tag ring oscillator frequency using the first backscattered frequency and the second backscattered frequency; and

determining an RFID tag temperature using, in part, a linear dependency of the RFID tag ring oscillator frequency, wherein the RFID tag temperature is determined using only the single local oscillator of the RFID tag.