Views: 159 Author: Site Editor Publish Time: 2021-01-08 Origin: Site
A precision balance calibration assesses the behavior of the chosen instrument. Calibration should only be performed by an authorized service technician. An adjustment changes the behavior of a weighing machine and requires an intervention which, in most cases, permanently alters the measuring instrument.
Precision is the number of digits in the number. The number of decimal places is the number of digits to the right of the decimal point. For example, the precision of the number 23.33 is 4 and the number of decimal places is 2.
In SQL Server, the default maximum precision for numeric and decimal data types is 38. While in earlier versions of SQL Server, the default maximum precision is 28.
The length of the number data type is the number of bytes used to store the number. For varchar and char, the length of the string is the number of bytes. For nvarchar and nchar, the length of the string is the number of byte pairs. For binary, the length of varbinary and image data types is the number of bytes. For example, an int data type can hold 10 digits, stored in 4 bytes, and does not accept a decimal point. The precision of the int data type is 10, the length is 4, and the number of decimal places is 0.
When concatenating two char, varchar, binary or varbinary expressions, the length of the resulting expression is the sum of the lengths of the two source expressions, up to 8,000 bytes. When concatenating two nchar or nvarchar expressions, the length of the resulting expression is the sum of the lengths of the two source expressions, up to 4,000-byte pairs.
By using UNION, EXCEPT, or INTERSECT to compare two expressions with the same data type but different lengths, the resulting length is the longer of the two expressions.
Except for decimal, the precision and decimal places of numeric data types are fixed. When an arithmetic operator has two expressions of the same type, the result will have the same data type and have the precision and scale defined for that type. If the operator has two expressions with different numeric data types, the data type precedence rules will define the data type of the result. The result has the precision and scale defined for its data type.
Precision balances, also called top loading balances, are a form of scale designed to offer highly accurate results, within the sub-milligram range. Used for the measurement of small samples, lab precision electronic digital balances provide an accurate, quick, and simple way of determining the weight of items such as particulate matter. Electronic precision balances offer a wide range of weighing capacities, with maximum capacities up to 64 kg.
They allow readability in the range of 1mg to 1 g, or 0-3 decimal places. High precision laboratory balances can extend this accuracy to 4 decimal places, on the display of the precision weighing balance, 0.0001g increments are used.
Precision balances for laboratory produce steady readings in a wider range of environmental conditions than analytical balances which must always be used under strict conditions to ensure accurate readings.
Being less sensitive to temperature fluctuations and air currents, high precision lab scales can serve as the more convenient method of measurement. While a draft shield is not always necessary for the accurate use of a laboratory precision balance, when working in a fume hood or under normal conditions with a high-resolution precision balance of 1mg readability, one should be employed to maintain performance.
When a precision balance is first connected to the power supply or switched on, a warm-up time of approximately 1-2 hours is recommended. This period allows the balance to adjust to ambient temperature and stabilize to its environment. This warm-up should be repeated every time the balance is turned on after a period of inactivity.