Frequently Asked Questions
Q: When is a 'Legal for Trade' scale necessary?
A: The government requires 'Legal for Trade' scales to be used whenever the scale is directly used in determing pricing in a transaction between the supplier and consumer.
Q: What are 'LCD' and 'LED' displays?
A: 'LCD'-Liquid Crystal Display, numbers are usually black, back-lights are often used for darker environments. 'LED'-Light-Emitting Diode, uses a semiconductor to emit light when a current is applied to it, usually red or green.
Q: What does the term 'wash-down' mean?
A: 'Wash-down' is used to describe water resistant devices. It does not mean water-proof.
Q: Aren't 'mass' and 'weight' the same thing?
A: No, 'mass' describes the amount of material in an object whereas 'weight' is the force produced when gravity acts on mass. Gravity is approximately constant on earth, so 'weight' is used more often than 'mass' when describing objects. Objects in orbit would have equal mass as when they're on earth, but produce no weight force in the absence of a gravitational field.
Q: What is 'Calibration'?
A: Calibration is the process of determing and/or establishing the numerical relationship between the observed output of a measurement system and the value of the characteristic being measure based on known reference standards. This also includes any steps required to ensure the accuracy and reliability of the procedure.
Q: Do I need my equipment calibrated? I paid a lot, I expect it to work.
A: The price has little to do with whether or when to calibrate your measuring device. Even though products and systems are designed for stability and long-term accuracy, many factors can affect performance and calibration. Simple things such as large temperature variances, rough handling during shipping, work-place accidents and operator error can either be a cause for or justify recalibration. It can become very expensive to reject parts because they measure out of spec. when the real problem was a measuring device that wasn't operating within tolerance. An appropriate calibration schedule will minimize the likelihood of this occurence.
Q: How often should my equipment be calibrated?
A: Any dimensional measuring device, from a simple dial caliper to a large capacity coordinate measuring machine, has a measurement range and resolution. It also has manufacturer spec's. for measurement accuracy, which the device is usually calibrated and verified to before shipment. It needs to be verified that all devices or systems meet purchased spec. after receipt, and before use. After verification, such devices can be accepted and used, with calibrations performed as recommended or required. If equipment receives heavy use, a regular calibration schedule should be considered to verify the performance is within spec.
Q: How do I establish a calibration frequency?
A: Many factors enter into the frequency of calibration, for example, the environment, part tolerances, regulatory agencies, and inherent equipment stability. According to ISO/IEC 17025:2005-General Requirements for the Competence of Testing and Calibration Laboratories, the Equipment Operator must determine the frequency of calibration. Ultimately it depends on hwo important the measuring device is to the manufacturing process. Rarely used measuring machines that are well maintained, kept in a controlled environment, and used properly may need calibration once a year. Measuring machines used to support production or used for product and process development might need monthly, quarterly, or perhaps more frequent calibrations.
Q: My parts have extremely tight tolerances, how do I know if error is from my parts or from the measuring equipment?
A: A useful method for solving this dilemma involves establishing a 'gold standard' so to speak for the parts in question. Take a sample that has been verified as being within tolerance/proper spec., and place that part in safe storage for periodic measuring. If an occassion arises where the performance of the device, or the quality of your parts, comes into question, measure the 'golden part' to look for variances in its measurements. If the reference part measures correctly then the problem is with your production process, and conversely if it measure incorrectly it is likely due to a problem with the measuring device.