![Package with ShockDot](https://upload.wikimedia.org/wikipedia/commons/8/8c/Package_with_ShockDot.png)
A shock detector, shock indicator, or impact monitor is a device which indicates whether a
physical shock or
impact
Impact may refer to:
* Impact (mechanics), a high force or shock (mechanics) over a short time period
* Impact, Texas, a town in Taylor County, Texas, US
Science and technology
* Impact crater, a meteor crater caused by an impact event
* Impac ...
has occurred. These usually have a
binary output (
go/no-go
A go/no go test is a two-step verification process that uses two boundary conditions, or a binary classification. The test is passed only when the ''go'' condition has been met and also the ''no go'' condition has been failed.
The test gives no in ...
) and are sometimes called ''shock overload devices''. Shock detectors can be used on shipments of fragile valuable items to indicate whether a potentially damaging drop or impact may have occurred. They are also used in sports helmets to help estimate if a dangerous impact may have occurred.
[Harris, C. M., and Peirsol, A. G. "Shock and Vibration Handbook", 2001, McGraw Hill, ISBN 0-07-137081-1]
By contrast, a
shock data logger is a
data acquisition Data acquisition is the process of sampling signals that measure real-world physical conditions and converting the resulting samples into digital numeric values that can be manipulated by a computer. Data acquisition systems, abbreviated by the acro ...
system for analysis and recording of shock pulses.
Overview
Shocks and impacts are often specified by the peak acceleration expressed in g-s (sometimes called
g-forces). The form of the shock pulse and particularly the duration are equally important.
[ For example, a short 1 ms 300 g shock has little damage potential and is not usually of interest but a 20 ms 300 g shock might be critical. Depending on the use, the response to this time sensitivity of a shock detector needs to be matched to the sensitivity of the item it is intended to monitor.
The mounting location also affects the response of most shock detectors. A shock on a rigid item such as a sports helmet or a rigid package might respond to a field shock with a jagged shock pulse which, without proper filtering is difficult to characterize. A shock on a cushioned item usually has a smoother shock pulse., and thus more consistent responses from shock detector.
Shocks are vector quantities with the direction of the shock being important to the item of interest, Shock detectors also can be highly sensitive to the direction of the input shock.][
A shock detector can be evaluated:
• Separately in a laboratory ]physical test A physical test is a qualitative or quantitative procedure that consists of determination of one or more characteristics of a given product, process or service according to a specified procedure. ASTM E 1301, Standard Guide for Proficiency Testing ...
, perhaps on an instrumented shock machine.
• Mounted to its intended item in a testing laboratory with controlled fixturing and controlled input shocks.
• In the field with uncontrolled and more highly variable input shocks.
Use of proper test method
A test method is a method for a test in science or engineering, such as a physical test, chemical test, or statistical test. It is a definitive procedure that produces a test result. In order to ensure accurate and relevant test results, a test m ...
s and Verification and validation
Verification and validation (also abbreviated as V&V) are independent procedures that are used together for checking that a product, service, or system meets requirements and specifications and that it fulfills its intended purpose. These are ...
protocols are important for all phases of evaluation.
Technologies
A wide variety of technologies are available ranging from simple analog indicators to more sophisticated electronics. Usually a device provides an optical indication of a triggered event but sometimes electrical or RFID signals can be provided. Hundreds of shock detectors are described in patents listed in Patent classification A patent classification is a system for examiners of patent offices or other people to categorize (code) documents, such as published patent applications, according to the technical features of their content. Patent classifications make it feasible ...
01P15/00: "Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration"
Most are based on:
* sensors such as accelerometer
An accelerometer is a tool that measures proper acceleration. Proper acceleration is the acceleration (the rate of change of velocity) of a body in its own instantaneous rest frame; this is different from coordinate acceleration, which is acc ...
s and associated Microelectromechanical systems[
*]Spring-mass system
In classical mechanics, a harmonic oscillator is a system that, when displaced from its equilibrium position, experiences a restoring force ''F'' proportional to the displacement ''x'':
\vec F = -k \vec x,
where ''k'' is a positive consta ...
s which can be triggered by a shock[
*Magnetic balls which can be dislodged from a holder][
*Disruption of the surface tension of a liquid
*Breakage of an inexpensive brittle component with a known fragility][
]
Monitor shipments
A shock detector can be mounted on a package (inside or outside) or directly on the product being shipped. Mounting on the package is usually done to detect excessive handling such as high drop heights while mounting on the product is done to more closely indicate product damage.[Yam, K.L., "Encyclopedia of Packaging Technology", John Wiley & Sons, 2009, ISBN 978-0-470-08704-6]
Some shipments need more than one shock detector to better monitor all directions of impacts.[ Large or long items sometimes have shock detectors at both ends of the shipping container.
The shock detector indicates whether the goods in transit were likely to have been subjected to potentially damaging conditions. Based on this data, the options may be:][
* If there have not been unusual shock, continue to use the shipment as is, without special inspection
* If potentially damaging hazards have occurred, thoroughly inspect the shipment for damage or conduct extra ]calibration
In measurement technology and metrology, calibration is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy. Such a standard could be another measurement device of kno ...
prior to use
* The consignee may choose to negotiate with the carrier, shipper, or supplier or even to reject a shipment where sensors indicate severe handling
Shock and impact are not the only hazards that can cause damage; vibration
Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be periodic, such as the motion of a pendulum—or random, su ...
, puncture, and compression can also cause damage yet would not trigger a shock detector.
Impacts to people
Personal protective equipment
Personal protective equipment (PPE) is protective clothing, helmets, goggles, or other garments or equipment designed to protect the wearer's body from injury or infection. The hazards addressed by protective equipment include physical, e ...
such as helmet
A helmet is a form of protective gear worn to protect the head. More specifically, a helmet complements the skull in protecting the human brain. Ceremonial or symbolic helmets (e.g., a policeman's helmet in the United Kingdom) without protect ...
s are sometimes equipped with impact monitors. These are intended to help managers know if an excessive impact has occurred and help direct needed rest or medical attention. Research is continuing, including specialized mouthgards to help classify head impacts.
Crash sensors on bicycle helmet
A bicycle helmet is a type of helmet designed to attenuate impacts to the head of a cyclist in falls while minimizing side effects such as interference with peripheral vision. There is ongoing scientific research into the degree of protection ...
s can detect a crash and call for assistance. Fall sensors are available to senior citizens to call for help when a fall is detected.
Other uses
A related use of an impact detector is as automobile air bag sensor. These sophisticated sensors are used to trigger the protective air bag system used on current vehicles.
Active hard-drive protection In computer hardware, active hard-drive protection refers to technology that attempts to avoid or reduce mechanical damage to hard disk drives by preparing the disk prior to impact. This approach is mainly used in laptop computers that are frequentl ...
systems sense impacts to laptop computer
A laptop, laptop computer, or notebook computer is a small, portable personal computer (PC) with a screen and alphanumeric keyboard. Laptops typically have a clam shell form factor with the screen mounted on the inside of the upper li ...
s to help minimize damage from drops.
Some emergency locator beacon
An emergency locator beacon is a radio beacon, a portable battery powered radio transmitter, used to locate airplanes, vessels, and persons in distress and in need of immediate rescue. Various types of emergency locator beacons are carried by air ...
s, such as Emergency Locator Transmitter
An Emergency Position-Indicating Radio Beacon (EPIRB) is a type of emergency locator beacon for commercial and recreational boats, a portable, battery-powered radio transmitter used in emergencies to locate boaters in distress and in need of ...
s, are activated by a specified shock or impact.
Interpretation
Shock detectors are used to indicate if a significant impact has occurred: This helps determine the need for follow-up actions. Variability is always present and must be accounted for in the analysis:
:* Shock detectors have some variation of response to shocks under controlled laboratory conditions.
:*People respond as individuals to impacts. What might cause injury to one person might not be as severe to another.
:*Fragile items and packaged goods respond with variation to uniform laboratory shocks,
:*Field shocks are highly variable
Of course, it is best when the shock detector properly signals when damage or injury is likely and when it is not. It is very possible to have false positive
A false positive is an error in binary classification in which a test result incorrectly indicates the presence of a condition (such as a disease when the disease is not present), while a false negative is the opposite error, where the test resul ...
signals where a shock detector is triggered but there is no damage to a product or no injury to a person. Likewise false negative
A false positive is an error in binary classification in which a test result incorrectly indicates the presence of a condition (such as a disease when the disease is not present), while a false negative is the opposite error, where the test resul ...
s are also possible.
Shock detectors are intended to indicate a single severe shock or impact. In some instances a series of lesser shocks might cause damage or injury but would not trigger a shock detector.
See also
*Type I and type II errors
In statistical hypothesis testing, a type I error is the mistaken rejection of an actually true null hypothesis (also known as a "false positive" finding or conclusion; example: "an innocent person is convicted"), while a type II error is the fa ...
*Concussions in sport
Concussions, a type of mild traumatic brain injury, are a frequent concern for those playing sports, from children and teenagers to professional athletes. Repeated concussions are a known cause of various neurological disorders, most notably chr ...
*Cushioning
Package cushioning is used to protect items during shipment. Vibration and impact shock during shipment and loading/unloading are controlled by cushioning to reduce the chance of product damage.
Cushioning is usually inside a shipping container ...
*Concussion grading systems
Concussion grading systems are sets of criteria used in sports medicine to determine the severity, or grade, of a concussion, the mildest form of traumatic brain injury. At least 16 such systems exist,
and there is little agreement among profe ...
*Head injury criterion
The head injury criterion (HIC) is a measure of the likelihood of head injury arising from an impact. The HIC can be used to assess safety related to vehicles, personal protective gear, and sport equipment.
Normally the variable is derived from t ...
*Football helmet
The football helmet is a piece of protective equipment used mainly in gridiron football, although a structural variation has occasional use in Australian rules football. It consists of a hard plastic shell with thick padding on the inside, a ...
* Sudden Motion Sensor
* Head impact telemetry system
*Evaluation of binary classifiers
The evaluation of binary classifiers compares two methods of assigning a binary attribute, one of which is usually a standard method and the other is being investigated. There are many metrics that can be used to measure the performance of a clas ...
*Confusion matrix
In the field of machine learning and specifically the problem of statistical classification, a confusion matrix, also known as an error matrix, is a specific table layout that allows visualization of the performance of an algorithm, typically a su ...
References
Bibliography
* DeSilva, C. W., "Vibration and Shock Handbook", CRC, 2005,
* Harris, C. M., and Peirsol, A. G. "Shock and Vibration Handbook", 2001, McGraw Hill,
* Yam, K.L., "Encyclopedia of Packaging Technology", John Wiley & Sons, 2009, {{ISBN, 978-0-470-08704-6
Helmets
Packaging
Measuring instruments
Mechanics
Safety engineering