Low-power shock detector and detection method

• US 6,138,516 A
• Filed: 12/17/1997
• Issued: 10/31/2000
• Est. Priority Date: 12/17/1997
• Status: Expired due to Fees

• Current Assignee: Weld Star Technology, Inc.
• Original Assignee: Weld Star Technology, Inc.
• Inventors: Tillman, Jennifer C.
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): MILLER, ROSE MARY
• Application Number:
  US08/992,615
• Time in Patent Office: 1,049 Days
• Field of Search: 340/429, 340/541, 340/566, 340/679, 340/683, 340/691, 340/981, 73/659, 73/660, 73/587, 73/593, 73/649, 73/651, 73/658
• US Class Current: 73/649
• CPC Class Codes: G01H 1/16 Amplitude

Abstract

A shock detector provides for ultra low power detection and measurement of damage to an object caused by shock and vibration. The shock detector includes a shock sensor, such as an accelerometer, attached to the object that produces an electrical vibration signal representative of the mechanical vibration of the object. A signal conditioning circuit determines when the magnitude of the electrical vibration signal exceeds a threshold voltage and converts the signal into a digital signal that is in the high voltage state when the magnitude of the electrical vibration signal is above the threshold voltage. Otherwise, the digital signal is in a low voltage state. A data logger records the time spent in the high voltage state. The measured time data and the threshold voltage are then used to estimate the damage applied to the object. Mounting a number of the conditioning circuits in parallel allows for a more accurate estimation.

Claims

1. An apparatus for detecting and measuring shock and vibration damage applied to an object comprising:

a shock sensor operatively attached to the object, the shock sensor adapted to generate an electrical vibration signal representative of a mechanical vibration applied thereto;

means for conditioning the electrical vibration signal to produce a high voltage state when the magnitude of the electrical vibration signal is above a threshold voltage and a low voltage state when the magnitude of the electrical vibration signal is below the threshold voltage;

means for measuring the time that the conditioned electrical vibration signal is in the high voltage state comprising an event counter connected to the means for conditioning the electrical vibration signal, the event counter adapted to activate when the conditioned electrical vibration signal is in the high voltage state, increment as long as the conditioned electrical vibration signal is in the high voltage state, and deactivate and remain inactive while the conditioned electrical vibration signal is in the low voltage state; and

means for storing the measured time that the conditioned electrical vibration signal is in the high voltage state comprising a data loger connected to the event counter, the data logger adapted to store the time measurements.

2. The apparatus of claim 1 further comprising:

means for determining the shock and vibration damage using the time measurements and the threshold voltage; and

means for storing the resulting shock and vibration damage.

3. The apparatus of claim 2 further comprising means for displaying the resulting shock and vibration damage.

4. An apparatus for detecting and measuring shock and vibration damage applied to an object comprising:

a shock sensor operatively attached to the object, the shock sensor adapted to generate an electrical vibration signal representative of a mechanical vibration applied thereto;

a plurality of means for conditioning the electrical vibration signal to produce a high voltage state when the magnitude of the electrical vibration signal is above a threshold voltage and a low voltage state when the magnitude of the electrical vibration signal is below the threshold voltage;

each of the means for conditioning the electrical vibration signal having a different threshold voltage;

means for measuring the time that the conditioned electrical vibration signal is in the high voltage state for each of the means for conditioning the electrical vibration signal;

means for storing the measured time that the conditioned electrical vibration signal is in the high voltage state for each of the means for conditioning the electrical vibration signal as well as the threshold voltage associated with the measured time that the conditioned electrical vibration signal is in the high voltage state;

means for determining the shock and vibration damage using the time measurements and the threshold voltage that integrates the incremental threshold values of the plurality of means for conditioning the electrical vibration signal; and

,

means for storing the resulting shock and vibration damage.

5. An apparatus for detecting and measuring shock and vibration damage applied to an object comprising:

an accelerometer operatively attached to the object, the accelerometer adapted to generate an electrical vibration signal representative of a mechanical vibration applied thereto;

the accelerometer adapted to generate an electrical vibration signal without requiring continuous power;

a rectifier connected to the accelerometer, the rectifier adapted to receive the electrical vibration signal from the accelerometer as a rectifier input signal thereto and adapted to transmit a rectifier output signal corresponding to the absolute value of the electrical vibration signal;

a comparator connected to the rectifier, the comparator adapted to receive the rectifier output signal as a comparator input signal thereto and adapted to generate the threshold voltage and compare the comparator input signal to the threshold voltage and transmit as a comparator output signal a low voltage state when the comparator input signal exceeds the threshold voltage and a high voltage state when the comparator input signal is equal to or less than the threshold voltage;

an inverter connected to the comparator, the inverter adapted to receive and invert the comparator output signal so that the inverter transmits as an inverter output signal a high voltage state when the comparator input signal exceeds the threshold voltage and a low voltage state when the comparator input signal is equal to or less than the threshold voltage;

a potentiometer connected to the comparator, the potentiometer adapted to permit the threshold voltage to be varied;

an event counter connected to the inverter, the event counter adapted to receive the inverter output signal and adapted to activate when the conditioned electrical vibration signal is in the high voltage state, increment as long as the conditioned electrical vibration signal is in the high voltage state, and deactivate and remain inactive while the conditioned electrical vibration signal is in the low voltage state;

a data logger connected to the event counter, the data logger adapted to receive and store the time measurements from the event counter;

means for determining the shock and vibration damage using the time measurements and the threshold voltage; and

means for storing the resulting shock and vibration damage.

6. A method for detecting and measuring shock and vibration damage applied to an object comprising:

electrically detecting a mechanical vibration of the object and producing an electrical vibration signal representative of the mechanical vibration;

electrically conditioning the electrical vibration signal to produce a high voltage state when the electrical output signal is above a threshold voltage and a low voltage state when the electrical output signal is below the threshold voltage;

measuring the time the conditioned electrical vibration signal is in the high voltage state;

storing the measured time that the conditioned electrical vibration signal is in the high voltage state;

determining the shock and vibration damage using the time measurements and the threshold voltage; and

storing the resulting shock and vibration damage.