Moisture meter

• US 20030169054A1
• Filed: 06/19/2002
• Published: 09/11/2003
• Est. Priority Date: 03/08/2002
• Status: Active Grant

• Current Assignee: Rynhart Research Limited
• Original Assignee: Rynhart Research Limited
• Inventors: McIlroy, James, Rynhart, Alan, Fallon, Sean
• Granted Patent: US 6,747,463 B2
• Time in Patent Office: Days
• US Class Current: 324/649
• CPC Class Codes: G01N 27/223 for determining moisture content, e.g. humidity rain detectors on vehicle windows B60S1/0825
• CPC Class Codes: G01N 33/46 Wood

Abstract

A moisture meter (1) has a capacitive sensing circuit (11-16) feeding into a digital control circuit having a microcontroller (17). Input buttons (20, 22, 23) allow a user to select a material being surveyed. They also allow the user to instruct the meter (1) to hold a particular reading. This allows it to be more conveniently read. The output of the digital control circuit is fed via an ADC (18) to a moving coil meter (4). This provides an easy-to-read display in which trends as the meter (1) is moved across a surface are easy to track.

Claims

1. A moisture meter comprising:

a moisture sensor;

a digital control circuit comprising means for processing output signals from said sensor and for generating and storing moisture measurements; and

an output interface comprising a digital to analogue converter (DAC) connected to the digital control circuit, and an analogue display device comprising means for providing an analogue moisture display in response to outputs of the digital to analogue converter.

2. A moisture meter as claimed in claim 1, wherein the analogue display device comprises a moving coil meter.

3. A moisture meter as claimed in claim 1, wherein the moisture meter comprises means for linearising moisture readings.

4. A moisture meter as claimed in claim 3, wherein the linearising means comprises a logarithmic amplifier in the sensor.

5. A moisture meter as claimed in claim 4, wherein the logarithmic amplifier is connected between a sensor amplifier and an analogue to digital converter (ADC) of the digital control circuit.

6. A moisture meter as claimed in claim 1, wherein the digital control circuit comprises an input interface comprising means for allowing user selection of a desired material.

7. A moisture meter as claimed in claim 6, wherein the input interface comprises a user button for selecting a material.

8. A moisture meter as claimed in claim 6, wherein the digital control circuit comprises means for generating an interrupt upon user selection of a material.

9. A moisture meter as claimed in claim 6, wherein the digital control circuit comprises means for storing a flag indicating the selected material when the moisture meter is powered down, and for activating with the same material at power-up.

10. A moisture meter as claimed in claim 1, wherein the digital control circuit comprises means for locking to a current reading in response to user selection of a hold function at the input interface.

11. A moisture meter as claimed in claim 10, wherein the digital control circuit comprises means for generating an interrupt upon user selection of the hold function.

12. A moisture meter as claimed in claim 1, wherein the digital control circuit comprises means for operating in timed loops of monitoring sensor signals, processing the signals, and outputting a moisture reading.

13. A moisture meter as claimed in claim 1, wherein the digital control circuit comprises means for powering-down to a sleep mode after expiry of a timeout period for a single reading.

14. A moisture meter as claimed in claim 13, wherein the digital control circuit comprises means for activating a timer when a timed processing loop generates the same reading as that for the previous processing loop, whereby the timeout period is calculated from the time at which a reading has not changed.