What types of audible alarms are available in today's marketplace?
There are two primary types of audible alarms: piezo electric and electromechanical. Audible alarms are also sometimes called buzzers.
What is a piezo audible alarm and how does it work?
Piezoelectric audible alarms are alarms that use very efficient piezo crystal wafers that have been bonded to a metal disk. When voltage is applied to the piezo wafer it deforms in proportion to the voltage applied. If an electronic signal in the audible hearing range is applied to this crystalline wafer the metallic disk will vibrate at this audible frequency. The sound pressure produced by this disk is very low without using the resonant properties of a tuned cavity (alarm body, or case) to boost this small signal. The use of an efficient piezo crystal, coupled with a specially tuned body, produces a high output alarm that consumes very little current.
What is piezoelectricity?
Piezoelectricity, discovered in the 1880's during experiments on quartz, is produced from the interrelationship of a material's mechanical and electrical properties. In essence, when a piezoelectric material is squeezed, an electrical charge collects on its surface. Conversely, when a piezoelectric material is subjected to a voltage drop, it mechanically deforms.
Many crystalline materials exhibit piezoelectric behavior. A few materials exhibit the phenomenon strongly enough to be used in applications that take advantage of their properties. These include quartz, rochelle salt, lead titanate zirconate ceramics (e.g. PZT-4, PZT-5A, etc.), barium titanate, and polyvinylidene flouride (a polymer film).
On a nanoscopic scale, piezoelectricity results from a non-uniform charge distribution within a crystal's unit cells. When such a crystal is mechanically deformed, the positive and negative charge centers displace by differing amounts. So while the overall crystal remains electrically neutral, the difference in charge center displacements results in an electric polarization within the crystal. Electric polarization due to mechanical input is perceived as piezoelectricity.
From an engineering or modeling point of view, piezoelectricity results in a change to a material's constitutive properties. Many finite element codes include piezoelectric modeling capability.
What is an electromechanical audible alarm and how does it work?
An electromechanical audible alarm is an electrical device that produces a sound intended to attract attention. It operates on electromagnetic principals. When power is applied to the unit, current flows through a coil, which produces a magnetic field. The magnetic field then pulls a metallic contact toward the coil, thereby causing the contact to open the circuit, which in turn interrupts the flow of current. Because the current has been interrupted, the coil loses its magnetic field, thus releasing the contact to its original position. As the contact resets, the current's flow is restored and the process is repeated continuously, thus producing sound, until the power is deprived to the unit.
What are the differences between a piezo versus an electromechanical audible alarm?
A piezoelectric alarm has a small profile, has no moving parts, is less susceptible to wear and component fatigue, is more environmentally secure, can perform in marine environments, draws very little current (in many cases 1/10th that of electromechanical devices), and has the flexibility of producing higher sound output when greater input voltage is applied.
On the other hand, electromechanical alarms have a number of mechanical, moving parts, are susceptible to wear, component failure and the elements, particularly humidity, fresh and salt water. They also consume a significant amount of current, and in order to produce more sound, even more current is required. In addition, they are often significantly larger due to the size, nature and number of component parts.
Why is a piezo alarm preferable to an electromechanical alarm?
An electromechanical alarm has a limited operating life cycle due to the mechanical operating characteristics of that type of alarm. The electrical contact inside the alarm that keeps opening and closing typically has a high failure rate. First, the contact arcs as it opens and interrupts the current flow. This repeated arcing burns the contact and over time will eventually leave the circuit open. The second problem is metal fatigue on the metallic contact. Also, electromechanical alarms can draw up to ten times the current of a piezo alarm.
A piezo alarm is superior in many ways to an electromechanical alarm. Piezo alarms do not have any mechanical devices that move, and thus are not susceptible to breakdowns due to fatigue or contact arcing. In addition, piezoelectric alarms are more versatile and can perform in a much wider variety of environmental settings. Also, piezo alarms have a small profile and draw very little current, thus they are suitable for a wide variety of applications. In fact, electromechanical devices consume power up to ten times faster, making piezo alarms more attractive in battery powered applications.
What types of applications typically lend themselves to a piezo audible alarm solution?
Piezo alarms are perfectly suited for a wide variety of applications such as fluid level detection, temperature level detection, movement alerts, elevator chimes and metal detectors, to name a few.
Industries that commonly use piezo alarms include automotive, air and ground transportation, marine (both commercial and recreational), agricultural, control panel manufacturers and industrial equipment manufacturers, to name a few.
What types of applications typically lend themselves to an electromechanical audible alarm solution?
Electromechanical devices are most commonly used as horns or buzzers that enable an operator to initiate an alert into the surrounding environment.
What factors must be considered in selecting a piezo audible alarm?
There are five primary criteria to consider in selecting a piezo audible alarm:
Are Floyd Bell Inc. piezo audible alarms "Made in the USA?"
Yes. Floyd Bell Inc. is the only piezo audible alarm manufacturer that domestically produces all of the alarms that it sells. All other domestic alarm manufacturers sell alarms that are manufactured overseas.
Piezo electric audible alarms are available from several manufacturers. What sets Floyd Bell Inc. alarms apart?
Floyd Bell Inc. manufacturers the most sophisticated piezo alarms in the world. Floyd Bell alarms are comprised of an average of 17 electronic components, while many piezo alarms are comprised of an average of just 3 electronic components. As a result, Floyd Bell alarms offer vastly enhanced functionality, versatility, stability, reliability protection and performance.
For instance, Floyd Bell alarms have:
Most competing alarms, on the other hand:
What is the industry standard for measurement of the loudness of an audible alarm?
The loudness of an alarm is also known as sound pressure. Sound pressure is expressed in terms of decibels (dB). In shopping for an alarm, the customer will of course want to know the loudness of the alarm. However, loudness will vary depending upon the listener's distance from the alarm.
The industry standard measures the dB level from a distance of 2 feet (0.61 M) from the alarm. Thus when you see in a product description that an alarm produces 102 dB, that should mean 102 dB at a distance of 2 feet from the alarm.
CAUTION: Some alarm vendors will express the decibel level of their alarms at a distance of only 1 foot from the alarm in order to exaggerate the sound performance of their alarms. It is imperative to read the fine print. A 102 dB alarm at 1 foot translates into a dB level of only 96 at 2 feet (see the sound degradation formula in answer to the next question). Other vendors will measure their sound output at 10 centimeters (4 inches). A 102 dB alarm at 10 centimeters is the equivalent to only 86 dB at 2 feet.
What is the formula for calculating the decibel level at any given distance from the source? For example, what if I need 82 decibels of sound output at a distance of 16 feet away from the alarm for my particular application? What decibel level of alarm must I purchase in order to accomplish this?
Decibel levels decrease as you move away from the source, and correspondingly increase as you move toward the source. Every time you double the distance from the source you subtract 6 dB. Every time you halve the distance to the source, you add 6 dB. So in our example, in order to achieve 82 dB at 16 feet, you will need an alarm that produces 100dB of sound at a distance of 2 feet from the alarm.
Going from 2 feet to 4 feet, a loss of 6 dB occurs. Going from 4 feet to 8 feet, another 6 dB loss occurs. Then going from 8 feet to 16 feet, another 6 dB occurs, for a total loss from 2 to 16 feet of 18 dB. So a 100 dB alarm at 2 feet is identical to an 82 dB alarm at 16 feet. Said another way, 2 feet has to be doubled 3 times in order to get to 16 feet. 3 times the 6 dB of sound loss every time the distance is doubled equals a sound degradation of 18 (3 x 6 = 18).
What effect does housing an alarm in an enclosure have on the loudness of the alarm?
Typically, when a customer's specific application calls for an alarm to be located inside an enclosure rather than fully exposed to the ear, you can expect, on average, a loss of approximately 20 decibels. This will of course vary depending upon the wall thickness of the enclosure and other environmental conditions.
What is the sensitivity of the human ear to variations in sound levels?
Studies have shown that the human ear detects changes in sound levels in approximately 3-decibel increments.
How much louder is a 100 dB alarm than a 90 dB alarm?
Increases in loudness are not linear, but are instead logarithmic. A general rule of thumb for loudness is that at these decibel levels, an additional 10 dB of sound is perceived by the human ear to be twice as loud.
What power is required in order to make a sound source twice as loud?
A general rule of thumb for loudness is that the power must be increased by about a factor of ten to produce a sound that is twice as loud.
What type of tone is best for noisy factory conditions?
Tones that sweep or are modulated in frequency and do not blend into the surrounding ambient sound are the most noticeable in noisy environments. Floyd Bell's staccato and siren tones work well in such environments.
Are Floyd Bell, Inc. alarm units water resistant?
Yes. Floyd Bell alarms are water resistant. Each alarm is hand-sealed and then epoxy potted to protect the electronic components from moisture. Also, all Floyd Bell alarm bodies are all specially treated with a corona process that ensures maximum adhesion of the epoxy potting to the body surface. At the opposite end of the alarm you will find the sound chamber with an opening that emits the sound. Alarms should be oriented within the particular application so that the water can drain from the sound chamber opening to avoid "ponding." Significantly, all Floyd Bell alarms use a more expensive stainless steel bender (diaphragm) that provides maximum corrosion resistance.
Floyd Bell alarms are built to withstand exposure to salt spray per ASTM B117 for a period of 300 hours with no decrease in sound output.
CAUTION: Most other audible alarm manufacturers use brass diaphragms (benders) because they cost about half as much as stainless steel, however, those alarms are highly susceptible to corrosion.
When used with our gasket, Floyd Bell alarms meet NEMA Type 4x requirements.
What does it mean to say that Floyd Bell Inc. alarms meet NEMA Type 4x requirements?
NEMA (the National Electrical Manufacturers Association) is a North American organization that creates standards for the rating of enclosure performance to determine an enclosure's ability to resist external environmental influences. The NEMA Type 4x standard is for enclosures that are intended for indoor or outdoor use primarily to provide a degree of protection against corrosion, windblown dust and rain, splashing water, hose-directed water, and the formation of ice on the enclosure.
Why is a stainless steel diaphragm (bender) better than a brass diaphragm?
All Floyd Bell alarms use as a premium component: hand-wired stainless steel diaphragms (benders). Floyd Bell chose that material because its alarms are designed have the physical dexterity to withstand a broad range of exacting environmental conditions, including fresh and salt water. Floyd Bell's #304 stainless steel diaphragms, which cost about twice as much as brass diaphragms, provide the most corrosion resistant piezo alarms available in the world.
How do Floyd Bell Inc. alarms respond to humid environments?
All of our alarms are rated to withstand relative humidity of up to 95% at +40 degrees C continuously for 100 hours.
What is the typical lead time for Floyd Bell Inc.'s standard product line?
The products shown in the online catalog located on this web site are generally in stock in reasonable quantities. The lead time for products shown in our master catalog that are not shown in our online catalog may well be in stock, but if not, expect anywhere from 48 hours from the time the order is placed, to 4 weeks depending on quantity required, the complexity of the product, and availability of components required for the particular application.
What is the typical lead time for custom products from Floyd Bell Inc.?
The process from consultative design through a fully tested product can take anywhere from 1 to 4 weeks, depending upon the complexity of the product and the availability of required components. Thereafter, production runs will take anywhere from 1 to 4 weeks, depending upon quantities, the complexity of the product, availability of components and whether a blanket order with reliable forecasting is in place.
Can Floyd Bell, Inc. custom design and build an alarm to meet a customer's special application?
Yes. Floyd Bell has an experienced engineering staff that can coach a customer through the process of determining a customer's application-specific needs, and then design, build and test an alarm that will meet those needs. Floyd Bell can create special tones, voltage ranges, mounting configurations and custom terminations, including various wiring harnesses.
Please check out Floyd Bell's Design Guide located in the DOWNLOAD area of this web site, or contact our Sales Department for assistance with your alarm design.
Why would I purchase from Floyd Bell Inc. when I can buy a cheaper alarm made overseas?
Alarms made overseas may appear to be an attractive alternative to domestically produced piezo alarms, largely because of price, but there are significant trade-offs in terms of quality, reliability, functionality, flexibility, delivery times and problem resolution.
All Floyd Bell alarms are made in the U.S.A, and:
What is the normal life expectancy of a Floyd Bell Inc. alarm?
All Floyd Bell alarms have a life expectancy under normal operating conditions of 10 years.
What is the warranty period for a Floyd Bell Inc. alarm?
All Floyd Bell alarms contain a limited warranty for a period of one year or one hundred (100) hours of continuous operation from the date of manufacture.
What happens if the alarm's polarity is reversed when connecting to the power source?
All Floyd Bell alarms contain special circuitry that protects against accidental reverse polarity connection, up to the alarm's maximum operating voltage. Most competing alarms do not contain this feature.
Are Floyd Bell Inc. alarms protected from power spikes?
All Floyd Bell alarms contain special circuitry that protects against power surges. They are rated to provide protection up to 20% over the maximum rated voltage for less than 5 minutes.
Does Floyd Bell Inc. stock a minimum inventory of customer parts as safety stock for fast response to changes in demand?
Floyd Bell routinely keeps a minimum safety stock on the shelf for customers that have a blanket order in process and wish to have a stock of alarms that can be shipped on a moment's notice if a spike in demand or change in production scheduling should occur.
Are Floyd Bell Inc. alarms able to withstand vibration?
Yes. Floyd Bell's manufacturing process produces alarms that are able to withstand vibration and other similar environmental stresses. Specifically, they are rated to withstand vibrations of between 0 and 55 Hz on all axes.
How are Floyd Bell, Inc. alarms units enclosed and sealed?
Each Floyd Bell alarm is enclosed in a case (also referred to as a "body") made of hard plastic NORYL® N-190 flame-retardant UL 94-VO made by GE Plastics. The components are then encased with a potting material made of 2 parts black epoxy resin. Also, all Floyd Bell alarm bodies are specially treated with a "corona" process that conditions the body surface to ensure maximum adhesion of the epoxy to the body walls.
Are Floyd Bell, Inc. alarms flame resistant?
Yes. Each Floyd Bell alarm is enclosed in a flame-resistant case (also referred to as a "body") made of hard plastic NORYL® N-190 UL 94-VO made by GE Plastics.
Are Floyd Bell Inc. ultra violet resistant?
Yes. Each Floyd Bell alarm is enclosed in an ultra violet resistant case (also referred to as a "body") made of hard plastic NORYL® N-190 UL 94-VO made by GE Plastics. Also, the black epoxy potting solution that encases the alarm's components is also UV resistant.
Are Floyd Bell, Inc. alarms UL recognized?
Yes. Please click on the links below, one of which will take you directly to the Floyd Bell online UL listing in the United States, and the other of which will take you to Floyd Bell's Canadian UL online listing. If you desire a UL recognized custom part please contact us and we will accommodate your needs.
Floyd Bell's assigned UL file number on the UL web site is S3897. The relevant UL category is "Audible Signal Appliances, General Signal Component."
UL United States: click here
UL Canada: click here
What are "terminations," and what types of terminations are available on Floyd Bell Inc. alarms?
Terminations are the electrical connections built into each Floyd Bell alarm that transmit electrical impulses to and from the application, and over which power is supplied to the alarm. Terminations are described in detail in the Product Numbering Scheme and Glossary:
What is the termination strength of Floyd Bell Inc. alarms?
Floyd Bell alarms are made to withstand a pull test to a maximum load of 22 pounds (10kg).
Can Floyd Bell Inc. provide custom terminations for a customer's unique application?
Yes. Floyd Bell will work with its customers to provide custom terminations based upon the application and the number of units required. Our Komax machine allows us to manufacture wire harnesses to our customer's precise specifications, thus reducing costs by cutting out the wire house middleman, and enabling seamless, production-quality integration of alarms with wire harnesses. This also provides a single point of contact with clear vendor responsibility for the combined product.
What are "plated thru holes?" Does Floyd Bell Inc. use plated thru holes in its alarms?
Printed circuit boards are the foundation of piezo audible alarms. All of the circuitry of the alarm and the alarm's terminations are organized by, and affixed to the PCB's through holes in the PCB's. It is the conductive connections of the various components on the PCB that ensure the successful long-term operation and reliability of the alarm. In order to maximize the continuous conductive connection of all circuits and electrical components, Floyd Bell uses only plated thru holes. In other words, rather than rely simply on conductive material placed on the surface of the PCB (which is how most piezo alarm vendors build their alarms), Floyd Bell places conductive material on both the surface and throughout the PCB holes themselves to enable maximum conductive connection of all components. Additionally, we double solder all of our connections. The combination of plated thru holes and double soldering makes our alarms the most durable and reliable in the industry.
Does Floyd Bell Inc. utilize double soldering in the assembly of its alarm components?
Yes. Floyd Bell double solders all of its connections. The combination of plated thru holes, described above, combined with double soldering of all connections, makes Floyd Bell alarms the most durable and reliable in the industry.
Does Floyd Bell Inc. utilize both precision primary and secondary oscillators, and why?
Yes. Floyd Bell uses both precision primary and precision secondary oscillators. This means that the sound frequency output of Floyd Bell alarms is very precise, which provides desired stability and uniform sound output to ensure that the sound remains consistent with the customer's unique application.