Scale Components & Features|
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There are two main specifications for scales. For example, here at RightOnScales you may see a scale listed with specs of 100g x 0.1g.
This means the scale has a Maximum Capacity of 100 grams with an Accuracy of 0.1 gram
This is the most weight a scale is designed to weigh at one time. If more than the max weight is placed on the tray at one time (even if the scale is off) damage will occur to the Load Cell. When in use, most scales will display "EEEEE" or similar to indicate too much weight.
How do I know How Much Capacity I Need? That's purely up to you and how much weight you need to weigh at one time.
Also referred to as resolution and readability. This is the smallest amount of weight the scale is able to see, which determines how accurate the scale is.
See the following examples of various scale accuracies, and how a scale with that particular accuracy registers weight.
0.002g Accuracy: 0.002, 0.004, 0.006, 0.008, 0.010, 0.012...
0.01g Accuracy: 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11...
0.05g Accuracy: 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50...
0.1g Accuracy: 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1...
0.5g Accuracy: 0.5, 1.0, 1.5, 2.0, 2.5, 3.0...
1g Accuracy: 1, 2, 3, 4, 5...
For example, if you only needed to make your measurements to one gram (1g, 2g, 3g...) then a scale with a 1g accuracy would work fine. However if you needed to make a measurement to 1.8 grams, then you would need a scale with an accuracy of 0.1g to weigh your sample correctly.
Note that grams are used in the above example. Scales often weigh in many different weighing modes (ounces, carats, troy counces, etc). A scale's specifications will always provide the Max Capacity and accuracy in each weighing mode the scale has.
What if I weigh something that weighs less than my scale's accuracy? Let's take a scale with 1g accuracy. If we place 0.1g of weight on the tray the scale will still register zero (also see Auto Zero). If 0.5g is placed on the tray the scale will probably fluctuate between 0g and 1g.
Scales round up and down at different points depending on the components of the scale and their design. The point is a scale with 1g accuracy will not effectively register weight less than 1g. The same holds true for all scales and their posted accuracies.
Check the posted accuracy for the scale you are considering and make sure it provides enough accuracy for your application.
How do I know How Much Accuracy I Need? That's purely up to you and how accurate you need to make your measurements. As mentioned above, be sure the posted accuracy for the scale you are purchasing matches the amount of precision you need to make your measurements to.
Note that as accuracy increases so does price. Also as accuracy increases, Maximum Capacity of the scale generally decreases. (Also see Divisions)
Also see our handy Weight Converter.
Resolution: See Accuracy
Readability: See Accuracy
Size is one of the first things to consider. How big of a weighing tray do you need? This will depend on your weighing application. Smaller scales will be more portable than larger ones, but have a smaller weighing tray. Do keep in mind that an Expansion Tray or Weighing Container can be used on any scale. This will increase the tray size and/or increase the volume of sample that can be weighed at one time.
Smaller scales usually only run from batteries, while larger scales often have the option of using AC adapter power in addition to batteries (also see Batteries/Power).
People new to digital scales often have the most questions regarding calibration and calibration masses. All the digital scales on our site come pre-calibrated from the factory and are ready for use right out of the box.
However, over a period of time and after being subjected to a lot of bumping around (like during shipping) a scale's readings may drift slightly.
When is re-calibration required? For example, if we place a 100g mass on the tray of a scale with 0.1g accuracy and it's more than 0.3g off we recommend re-calibration. Anything within three Divisions is usually fine.
Also note that Air Currents, Vibrations, and other Environmental Factors can interfere with your scale's readings.
What does calibration do? Calibration requires a calibration mass or masses. The calibration mass required for each scale varies, and the user manual will tell you exactly what mass is needed.
When a scale is re-calibrated correctly it is resetting the scale's computer to the reference weight you are placing on the tray. In other words, by placing the cal mass on the tray you are reminding the scale exactly what that 100g mass weighs. By doing so, it will reset itself according to the cal mass and its readings will again be right on the money.
Optional Calibration Masses. Some scales include the calibration mass with the scale. With other models, the calibration masses are an optional accessory. People always want to know if they should spend the extra money for the cal mass or not.
For scales will smaller calibration masses like a few hundred grams, the masses are relatively cheap and do not add much to the shipping weight of your order so we suggest you do pickup the cal mass.
However, some scales require many kg of calibration weights. These weights are expensive and very heavy to ship. In cases like these we remind customers the scale comes pre-calibrated and ready to go, and that the calibration masses are not a necessity. Also keep in mind you can always come back later and order the cal masses from us as long as you purchased your scale with us.
Note that not all scales are meant to be re-calibrated by the end user. Always refer to your User Manual.
Calibration Gone Bad. Some customers assume that all scales need to be recalibrated as soon as they come out of the box, or even before each use which is not true. In the worst cases these customers may not even have the correct calibration mass or may have no masses at all. Then top it off by not reading the calibration instructions and you have one messed up scale. Improper calibration will render your scale useless. Always be sure to follow the instructions in your User Manual.
Calibration masses do come in several different classes. Each class of masses have a different tolerance, this refers to just how close the mass has to be to the weight it is suppose to be. At RightOnScales all masses are of the correct class for the scale it is being sold for.
ANSI/ASTM Class 1. For scales with 0.01mg to 0.1mg accuracy.
ANSI/ASTM Class 2. For scales with 0.001g to 0.01g accuracy.
ANSI/ASTM Class 3. For scales with 0.01g to 0.1g accuracy.
ANSI/ASTM Class 4. Appropriate for non-precision weighing.
Off Center Weighing
Also known as corner load, refers to how well a scale registers weight that is not placed directly on the center of the tray. A way to test this is to use a cal mass and see what the scale displays when the mass is placed in the center of the tray, then when the mass is moved to each corner of the tray.
Good scales should display the same weight for the mass no matter where on the tray it is placed, while scales of lesser quality may have a significant difference in the weight displayed when the mass is moved off center. Off center weighing is not a specification that is published by the manufacturer.
Divisions describes the total number of increments the scale is able to read. This term is used often to refer to the performance of the Weighing Sensor.
For example a scale with a 100g capacity that is accurate to 0.01g has a total of 10000 divisions.
A scale with a 100g capacity that is accurate to 0.1g has a total of 1000 divisions.
A scale with a 100g capacity that is accurate to 1g has a total of 100 divisions.
Repeatability is very similar to Linearity. Repeatability refers to a scale's ability to consistently deliver the same weight reading for a given mass, and to return to a zero reading after each weighing cycle.
You can test this by repeatedly weighing the same object. Repeatability is sometimes referred to as "Standard Deviation" of a set of similar weight readings. Repeatability is often an important specification for expensive commercial balances and is not a specification published by manufactures for the scales you will find here at RightOnScales.
Linearity is a term to describe how uniform the sensitivity of a scale is throughout its entire weighing capacity. Linearity is a specification usually only published for more expensive commercial scales and is not a specification provided for the scales you will find on our site.
Liquid Crystal Display (LCD) & Backlit LCDs
Almost all modern scales employ an LCD (Liquid Crystal Display) for the readout. LCD displays are inexpensive, reliable, consume a minimum of power and provide very high contrast readouts which are easy to read.
You will see Backlit LCDs offered on some models. Standard LCDs cannot be seen in darkness. But by adding a backlight, the entire display behind the numbers is illuminated, usually in a blue color. This allows the display to be seen in total darkness.
A downside to a backlit LCD is that the backlight does consume quite a bit more power when it is on, thus draining your battery faster than a non-backlit display. Manufactures have come to a compromise with this issue. By limiting the time the backlight remains on, usually to about 3 seconds after a weight is registered, the power drain is minimized. Some backlit models have a button to turn on and off the backlight, and others allow you to program how long the backlight remains on. With the backlight is off, the LCD operates just like a normal LCD. So turning off the backlight does not turn off the entire LCD.
Batteries & AC Adapters
Almost all pocket scales and compact scale models will run only from batteries. Tabletop and larger models will usually have the ability to run from AC adapter in addition to batteries.
Battery Types: There are two main types of batteries found in today's scales.
Alkaline: The first is the standard alkaline batteries which everyone is familiar with. Common alkaline batteries found in scales are AAA, AA, 9v, and C sizes. The benefit to these batteries is they are relatively cheap and most people have these batteries around the house. Alkalines do tend to have a shorter life span compared to the next type of battery, the lithium button cells.
Lithium Button Cells: Are found in many digital scales today. They offer a longer battery life compared to alkaline batteries. A pocket scale using lithium batteries can offer around 200 hours of usage on average, while Alkalines will tend to offer slightly less.
Lithiums are also very thin, allowing the scale to be made smaller.
In the past lithium batteries used to be difficult to find in stores when the time came to purchase a replacement. However, now a large selection of lithium batteries can be found in many national chain stores such as Home Depot, Wal-Mart, Radio Shack, drug stores and many other places. Lithiums still tend to cost slightly more than alkaline batteries so keep that in mind.
How long will my batteries last? That all depends on how often you use the scale and how long the scale is left on using battery power. Battery life will also depend on the scale model you are using and the type of batteries.
Also, batteries tend to loose their charge faster in hotter Temperatures. Manufactures always recommend that you remove the batteries from your scale if you are planning to store it for a long period of time. This will prevent any corrosion and preserve the life of your battery.
AC Power: AC power is nice to have if you plan on using your scale near an electrical outlet, or require prolonged uses of your scale. A lot of larger digital scales today will offer AC power along with battery power so you have the best of both worlds.
If your scale is able to run from AC power and the adapter is not included we highly suggest you purchase the correct corresponding AC adapter that was designed for your scale. Otherwise, using an adapter of the wrong voltage or connector can permanently destroy your scale and void your warranty.
Auto Power Off
Scale manufactures have developed the auto-off feature in order to prolong battery life and to prevent the scale from inadvertently being left on. If your scale were accidentally left on, your battery would be fully drained for the next time you tried to use it.
Auto-off is usually set to a two or three minute interval where if the scale does not register any input or change in weight, the scale will shut down. Some models have the auto-off programmable so you can set the time interval, or set it to disable auto-off all together.
Load Cells & Strain Gauge Transducers
The strain gauge, also known as the load cell, is the heart of any scale. This is the actual sensor component that registers the weight on the tray and converts that into an electrical signal which is then passed along to the other parts of the scale for processing.
Strain gauges come in two types, they are compression or tension.
A compression strain gauge is based on how much the cell compresses when pressure is applied, while a tension strain gauge is based on the slight change in shape of the cell caused by the weight.
The gauges are developed from an ultra-thin heat-treated metallic foil and are chemically bonded to a thin dielectric layer. The precise positioning of the gauge, the mounting procedure, and the materials used all have a measurable effect on overall performance of the load cell.
How does it work? Electricity is passed through the strain gauge. As weight is applied, the shape of the gauge changes. The change in shape also affects its resistance to the electric current being passed through it. By knowing precisely how much the electrical impedance changes in proportion to the weight being applied, the processing components are able to interpret the impedance change from the load cell into a weight, which is then displayed on the readout.
Exceeding the maximum capacity of a scale will almost always permanently bend the load cell. This means the load cell will not flex back to its original state when the weight is lifted as it was designed to do, thus overloading your scale and making it unusable.
Most digital scales at RightOnScales have a tare function, also referred to as zeroing out. Pressing the tare button at any time will return the scale display to zero. The most common use for tare is to zero out a Weighing Container or Expansion Tray.
Different scale models may use different terms for the same thing such as "zero", "tare", or just the character "Z" or "0" on the button itself. Scales that do not have a tare button may require you to turn the scale off, place the weighing bowl on the platform, then turn the scale back on. This will zero out the weighing tray, as the scale will go to 0.0 when it is powered back up. This is common in some of the kitchen scales like the Salters.
Using a weighing container or expansion tray allows you to expand the usable area of the scale's tray, and allow your scale to weigh more of your sample at one time.
Anything can be used for your weighing container, as long as the weight of your container and the weight of what you plan to weigh do not exceed the maximum capacity of your scale.
You will see listed in the specifications of some scales "tare to capacity by subtraction". This means the scale will Zero Out up to the Max Capacity of the scale
Some very sensitive scales may have an auto-zero function. Because they are so sensitive, scales like these tend to be a bit "jumpy" and will often fluctuate slightly from zero when nothing is on the tray. In order to correct this an auto-zero function keeps the scale at zero if it is within a few Divisions of zero in order to provide a steady zero reading.
The downside to auto-zero is if you are slowly adding a small amount of weight at a time to the tray, the scale may keep auto-zeroing as you add weight, resulting in an inaccurate reading. Please refer to the user manual for your scale for more information about the auto-zero function if your scale is equipped with this feature.
Digital scales consist of many electrical components, many of which utilize electrical resistance to provide accurate readings. The resistance of metal changes with temperature. Scales are designed to work best within a set temperature operating range which is usually posted with the scale's specifications.
Overall, scales work best at room temperature. Extreme heat or cold will affect your scale and most likely result in inaccurate readings. Extreme heat (like being left in direct sunlight) for example, will also render the LCD of a scale unreadable if it is heated up past a certain point. For best results treat your scale like the sensitive measuring device that it is, and always allow your scale to turn on and "warm up" before use in cold environments.
Scales are very sensitive, and will display any mass applied to the weighing tray. This includes mass applied by air currents. Very accurate scales such as those with an accuracy of 0.01g or more are most susceptible to air currents and other environmental factors. This will cause the readout to be "jumpy" and it will have a difficult time showing zero, or the weight of the sample on the tray.
Very sensitive balances often have a windscreen around the tray to prevent ambient air currents from interfering with the readings. And in the most sensitive scales, the weighing tray may even be in a vacuum chamber to prevent the weight of any dust particles from messing up your readings.
Vibrations and Air Currents are the two biggest problems people encounter with scale inaccuracies. It is common for us to get phone calls or e-mails from customers who are using their scale for the first time and are complaining the scale is jumping all over the place and will not provide an accurate readout.
It usually turns out the scale is being used in a location full of vibrations and air currents. Vibrations will travel from the surface the scale is sitting on and be transferred to the scale tray, which then reflects these vibrations on the display.
There is nothing wrong with the scale in this case, it is accurately displaying the weight and fluctuations it is getting from its weighing tray. Do not underestimate the accuracy of your scale, it will register many things you are not aware of in the environment.
Anything that emits Radio Frequencies (RF) can cause interference with your scale. This includes, but is not limited to, cell phones, cordless phone, TVs, computer monitors, and pretty much all electrical devices. A good rule of thumb is to not use you scale within proximity to any other electrical device.
One of our customers found that he was getting interference throughout his entire house, due to the high-voltage power lines which crossed over his house.
Not as big as a concern as the other factors above, but as with any electrical device, the build up of static electricity within your scale's components can interfere with your readings and in the worst cases destroy or damage some of your scale's components. If you feel your scale may be suffering from a static electricity build up, a solution is to gently rub it with an anti-static dryer sheet which will discharge the static.
Legal for Trade
Legal for trade is a certification by The National Type Evaluation Program (NTEP) which evaluates commercial measuring devices and issues Certificates of Conformance to those devices that meet national or international standards.
The most common legal for trade scale application is in the deli department of your grocery store. A scale that has been certified as legal for trade is insured to have the highest degree of reliability and accuracy so when consumers are charged based on the readout of that scale, they know they are being charged fairly for the goods being purchased.
Legal for Trade scales are very expensive and often lack many features found in other non-legal for trade models. Because of their extremely high price, RightOnScales does not currently carry any Legal for Trade models. Be sure to checkout our friends at Balances.com for a wide selection of Legal for Trade scales.
How do I know if I need a legal for trade scale? If you own a retail business and you are pricing goods for customers based solely on your scale, then chances are good you probably need a legal for trade scale. Be sure to check with your local city and county trade standards office to find out for sure.
In the diamond and gem industry, stones are most commonly weighed in carats. A stone's weight in carats, as in any measurement, can be expressed both as a decimal or factional number such as 0.75 ct or 3/4 ct.
Another common term is TCW. This refers to the Total Carat Weight of all the stones appearing on a single piece of jewelry. Earrings for example are often sold under the total carat weight of both pieces in the set.
When shopping for a digital carat scale most importantly you want to be sure the scale you are choosing weights in carats mode. We have a page of Carat Scales where all scales appearing in this listing weigh in carats mode.
Secondly, most professionals in the industry require their measurements to be made down to 1/100th of a carat (0.01ct). This is a very high level of precision.
Be sure you know just how much Accuracy you require for your carat weighing application.
If you have a question regarding any of our scales be sure to Contact Us.
Reloading your own ammunition is a favorite past time for many firearm enthusiasts. Ammunition is expensive and the costs continue to rise, however by reloading your own ammunition you can save a significant amount of money and make your shooting more cost effective.
Other benefits of reloading include being able to customize your ammunition specifically to your firearm and your personal preference. Reloading is a very rewarding hobby, but does require the right tools which includes your grain scale. Current knowledge of the reloading process and an eye for safety are also prerequisites to reloading your own ammunition.
Gunpowder is most commonly measured in units called grains (gn), not to be confused with grams (g). Almost all reloading applications require you to measure out powder down to 0.1 grain. For reference 0.1 grain equals approximately 0.006 grams, which is a very precise amount. Also see our handy Weight Converter.
Bioelectrical Impedance Analysis (BIA) is the method used by body fat scales to accurately measure a person's body fat percentage. It works by passing a small amount of electrical current from the scale through the user's body.
On most bodyfat scales there are two metal surfaces where the user's feet go. These are the conductors that pass a current through your body. The amount of current is very low so the user doesn't feel anything, but do know that people with pace makers or other implanted electrical devices should never use a body fat scale that employs BIA. The current may be enough to interfere with the pacemaker.
BIA measures the impedance or resistance to the signal as it travels through the water that is found in muscle and fat. The more muscle a person has, the more water their body can hold. The greater the amount of water in a person's body, the easier it is for the current to pass through it. The more fat, the more resistance to the current.
Parts counting is a special weighing mode offered on some scales.
A great application example for parts counting is beadwork, which can be very tedious when counting hundreds of beads by hand. A counting scale can save you a lot of time by being able to count out your parts by simply weighing a batch of them on the scale.
Before deciding if a counting scale will work for your application there are several things to consider. The first question is if the parts you plan to weigh on your counting scale are of uniform weight? If there are weight variations between your parts, the scale will not be able to accurately determine how many are on the weighing tray.
Secondly, you will need to know the weight of your pieces. Once you know this, you can then choose a counting scale with the appropriate accuracy. For example if your parts weigh exactly 0.5g each, a scale with an Accuracy of 1g will not work as it will not be accurate enough to see your individual pieces. In this example you would want a scale with a 0.1g Accuracy so that it will be able to correctly weigh and count your 0.5g pieces.
Finally, it is very important to note that even the most expensive counting scales will often be off by as many as a few pieces when weighing. Counting scales are never perfect, so if you need absolute perfection when counting each time, you're better off sticking to hand counting. However, for counting beads where being off by one or two beads is acceptable, parts counting scales are a great time saving tool. The more uniform in weight your parts are, the more accurate the counting will be.
How does it work? The scale must first be programmed. It needs to know the weight of your pieces so it can then determine how many are on the tray at one time. This process varies by scale so be sure to carefully follow the directions in your user manual. Almost always the scale will require you to place a sample of 10 or 20 pieces of your parts on the tray which will then be averaged and stored into the scale's memory. The scale is then programmed. Simply throw on a handful of beads, and the scale display will tell you how many are on the scale.
Be sure to see our page of Counting Scales.
Price computing is a feature that is great for anyone in the gem industry. The user is able to program in a price per weighing unit (such as per carat, gram, etc) then when the item is weighed the scale displays the weight along with the price according to the price formula entered by the user.
Some models allow several different pricing formulas to be entered into and saved in the scale's memory. Price computing is very common for deli scales and other legal for trade scales as well.