How Do You Make the Right Choice of Laboratory Balances?
Everything that exists in our world has a weight and therefore accurate weighing and weighing methods are very important. Therefore, the most important issue in this process is the correct weighing of the scales you use in weighing. The scales that you use in every field have a different feature and sensitivity. So you should use the right laboratory balance in the right place.
The same is true for the laboratory scales you use in the manufacturing sector. So how can you choose the right laboratory balance?
When choosing a laboratory scale, you should consider the purpose of the scale (drug weighing, chemical weighing, analysis work, etc.). Each laboratory balance has a different reading limit. You see this in the laboratory scale as the number of digits after zero. For example, on a laboratory scale of 0.000001g, the readability is 1μg. The smallest value readable by the laboratory balance (the readability of the balance), weighing capacity, etc. With many technical and physical features such as scales that can meet your needs.
When starting the selection of laboratory scales, you should remember that there are two types of laboratory scales with the desired technical characteristics. These;
1. Laboratory analytical balances show the weighing result in a range of 4 to 7 digits (0.0001g) after the comma.
This number of digits is also referred to as readability. The most common analytical balances show the result of four to five decimal numbers after zero, and you can usually use the powder to weigh chemicals and medicines in liquid or solid form. The maximum capacity can be up to 500g.
Inside the analytical balances, the microbalances display up to six decimal points that you can use for applications that require highly accurate measurements.
Ultra micro balances are the most accurate ones and you can measure up to 7 digits (0.1 μg) after the comma.
2. Laboratory precision scales are devices that can measure between 1 step and 3 steps (0.1 g-0.001 g) after the comma. You can use these scales when you need less precision and readability compared to analytical balances. In addition, if you want to weigh at high capacity, you can use these scales in your high capacity weighing because the weighing capacities of these scales are higher than analytical balances and because they can weigh in kilograms. These;
a) Weighing range / maximum weighing capacity,
b) Readability,
c) Scale accuracy,
d) Repeatability,
e) Linearity,
f) The smallest weighing amount (USP 41),
g) Working temperature,
h) Accuracy class,
i) Weighing pan,
j) Computer connection,
k) Balance inner chamber,
l) Scale cabinet.
a) Weighing Range
The scale weighing range is determined by the scale manufacturers and you should carefully monitor and select the scale for the highest weighing range. You should always bear in mind that if a weight greater than the maximum weighing weight is placed on the balance, damage to the balance may occur. So when choosing scales During the application, you can choose a balance with a capacity of 2 times the sample to be weighed. For example, if you are weighing 100g regularly, you can choose a balance with a capacity of 200g.
b) Readability
It is a parameter related to the maximum weighing capacity of the balance. You should pay attention to the mass of the measured sample and the accuracy to which it will be measured. When the analysis is done incorrectly, it may lead to a situation where your expectations or desired results do not occur. So if you are going to select a balance for a weighing that needs to read 0.0001g, you should choose a balance with a reading capacity of 0.00001g. This will give you the best precision for weighing.
c) Accuracy in Balance
Regarding the accuracy of the analytical balance, if you are weighing 100 g and want to work with 1mg accuracy with 0.01g / 10mg readability scale, you cannot tell whether the weighing result is 1mg. A balance of 1mg readability will give you a more accurate result if you take into account the accuracy of the 0.1mg resolution (readability) analytical balance.
d) Repeatability
It is the case where a scale is weighed with the same sample under the same measurement conditions, with the same result. Most of your questions relate to parameters that are described as “repeatability de in commercial examples for analytical balances. The better the reproducibility of the scale, the more accurate your results will be.
e) Linearity
It is expressed as the scale error in the weighing range of the scale. If you are using the scale within a very limited weighing range, you should perform the calibration at the point where you will weigh it. This is very important. Because the error is tested during measurements, the error is detected and adjusted for the entire weighing range.
f) Minimum Weighing Quantity (USP 41)
In the case of a drug-related weighing, in particular, you must determine the smallest amount that you can start weighing on the scale, as determined by the USP, depending on the technical characteristics of your balance. USP 41 specifies how to do this. In addition, scales provider companies specify this in their technical documentation and these providers certify it for you. Your task here is to choose and certify the balance according to the amount you will start weighing.
g) Working Temperature
These are the various temperatures guaranteed by the balance manufacturer for proper measurement. Therefore, because the operating temperature environment is different everywhere, you should be calibrated in environments where you will use scales. Otherwise, you will cause incorrect measurements.
h) Accuracy Class
The maximum allowed errors with respect to the verification unit. If you use your balance in a weighing, trading value, you must have chosen it with this feature and certify your balance from the national legal metrology institution.
i) Weighing Pan
You must select equal to the minimum size of the sample to be measured. You can also choose whether the pan is round or square, depending on the application. As a standard, we recommend the weighing pan to be selected as a pan with stainless steel technology (non-magnetic). If the cabinet which prevents the air flow is made of plastic without electrostatic charge, it will provide more sensitivity in your work.
j) Computer Connection
Today, almost all laboratory scales contain software. Depending on your needs, you can choose a balance with USB or RS-232 connections. In addition, if a large screen is required for the application in the balance, the touch and color display will be useful for you.
k) Scale Inner Chamber
It is mostly coated with aluminum (mostly legal metrological balances). You can also choose a plastic coated balance with a lower cost and chemical resistance. You can make the appropriate selection depending on your usage and according to your work.
l) Scale Cabinet
The analytical balances include a chamber that prevents the air flow outside the sample in the balance. You can choose different cabinet sizes according to your purpose of use (if you need high precision). But choosing a large cabinet balance can give you an advantage when the size of the sample you are going to weigh is large. In most scales, the weighing mechanism is just below the weighing pan and is less costly. For more sensitive scales (d = 0.1 mg), the weighing mechanism is located on the back of the scale.
In addition, if the electrostatic charge of the balance cabinets or the ion charge of the weighed liquid is a problem for you, you can choose a balance with systems that eliminate them.
You can also choose to include automatic or manual opening of the cabinets. This will increase the accuracy of your work by allowing you to open your scales cabinet without vibrating.
In some cases, samples containing ion-containing substances may be incorrectly weighed. In this case, it will be useful for you to choose scales where the weighing mechanism is quite far from the weighing pan (the weighing mechanism is behind the balance).
When selecting a balance, you must check whether the device has a type-approval certificate if you are going to use a metrological balance. During the validation process, the approving units will check for you whether the balance has the appropriate metrological properties and temperature error within the limits.
If you want to keep the weighing results in the balance memory, you should also consider this option when selecting the balance. Or, you can choose balance that can be used to transfer results to computer environment.
In addition to these features, if you want to be in the balance or if you want to make additional connections you can select the appropriate balance. Of them; if you want to print your results with the printer, do not take into account the GLP-enabled version or the only simple printout.
If you are going to use the balance in the pipette calibration, you must select the balance features that meet this feature. If you want to measure density, you should also request this density kit. All of these features are reflected in the product differently on different scales. Here you as a user for your priority weighing applications you want to make the desired technique (weighing capacity, balance repeatability, readability, balance accuracy, etc.) and physical (cabinet and pan size, computer connections, etc.) before you select the appropriate balance and then choose will be correct.
47Axx
Etekcity Digital Body Weight Bathroom Scale with Step-On Technology, 440 Pounds, Body Tape Measure Included