Q: What does the precision of various instruments mean?
A: Precision refers to how close a measured value is to the true or accepted value. It is often expressed as a percentage of the full scale. For example, an instrument with a precision of 0.5% means that its maximum error will not exceed 0.5% of the full scale reading. For a first-class instrument, the maximum error might be ±1%. If the full scale is 100A, the maximum allowable error would be 1A.
Q: What are absolute, relative, and folding errors in meters?
A: Absolute error is the difference between the meter's reading and the standard reference value. Relative error is the absolute error divided by the standard value, usually expressed as a percentage. Folding error, also known as percentage of full scale error, is the absolute error compared to the meter’s full scale range. These errors help determine the accuracy and reliability of the instrument during measurements.
Q: I often see symbols like ↑, →, and ∠45° on meters. What do they mean?
A: These symbols indicate the correct orientation for using the meter. The ↑ symbol means the meter should be placed vertically, → means it should be horizontal, and ∠45° indicates it should be tilted at 45 degrees from the horizontal. Using the meter in the wrong position can cause inaccurate readings and increase measurement errors beyond acceptable limits.
Q: What do the symbols on the dashboard represent?
A: Common symbols include those that indicate the required position (horizontal or vertical), whether the meter is designed for DC only, AC only, or both. These markings help users select the right meter for their application and avoid incorrect usage that could damage the device or produce unreliable results.
Q: Why do some meters have a lens on the dial?
A: A lens is used to reduce parallax error, which occurs when the pointer is viewed from an angle. The lens allows the user to align the pointer with its reflection, ensuring more accurate readings. This feature is especially useful in analog meters where the needle may not be perfectly aligned with the scale.
Q: Why do some meters have a metal film inside the casing?
A: The metal film acts as a shield against external magnetic fields. Since some meters, like electromagnetic ones, are sensitive to magnetic interference, the metal coating helps block these fields from affecting internal components. This shielding improves measurement accuracy, especially in high-precision instruments that may use two layers for better protection.
Q: Why are capacitors connected in parallel with electrical instruments in high-intensity equipment?
A: Capacitors are used to filter out high-frequency noise or interference caused by strong currents. By connecting a capacitor in parallel, it provides a low-impedance path for high-frequency signals, preventing them from affecting the meter’s readings. This ensures more stable and accurate measurements in noisy environments.
Q: Why shouldn't the measuring wires be tangled when using a megohmmeter to test insulation resistance?
A: If the wires are tangled, especially if the insulation is poor, it can create a parallel low-resistance path, leading to inaccurate readings. This can also affect the capacitance of the circuit being tested, making absorption ratio tests unreliable. To ensure accurate insulation resistance measurements, the wires should always be kept separate and properly arranged.
Input/Output Connector
Input/Output Connector
HuiZhou Antenk Electronics Co., LTD , https://www.atkconn.com