Analysis of Measurement Error and Multimeter Range Selection
When using a multimeter to measure, there will be some mistakes. Some of these inaccuracies are within the range of measurement errors permitted by the meter's accuracy class. Some are human errors brought on by misuse and poor adjustment. You can lessen measurement errors if you correctly comprehend the multimeter's properties and the reasons why measurements go wrong, as well as when you grasp the appropriate measuring procedures and strategies.
One of the factors that affects the measurement accuracy is human reading error. Though it cannot be avoided, it can be reduced. Consequently, pay close attention to the following factors when using:
1 Place the multimeter horizontally and conduct a mechanical zero adjustment before testing;
2 When reading, maintain a vertical gaze at the pointer;
3. Every time a gear is changed, the zero adjustment for measuring resistance must be done. Whenever the adjustment is less than zero, replace the battery with a new one.
4. To prevent shunting of human body resistance, increased measurement inaccuracy, or electric shock, do not squeeze the metal portion of the test lead with your hands when measuring resistance or high voltage;
5. After discharging the electricity stored in the capacitor and measuring the resistance in the RC circuit, turn off the circuit's power source. We analyze other faults after eliminating reading errors caused by humans.
1. Range selection and measurement inaccuracy for multimeter voltage and current
Multimeter accuracy ratings are typically broken down into a number of grades, including 0.1, 0.5, 1.5, 2.5, and 5. The calibration of the accuracy level is stated for DC voltage, current, AC voltage, and other gears by the percentage of the maximum permissible measurement error X and the full scale value of the chosen range. Written as a formula: A% = (X/full scale value) 100% 1
(1) Measuring the error caused by the same voltage with a multimeter of varying accuracy
(2) The mistake that results from using a multimeter with multiple ranges to measure the same voltage.
Measure the 23V standard voltage using the 100V block, and the multimeter will show a reading of between 20.5V and 25.5V. Measure the 23V standard voltage using the 25V block, and the multimeter will show a reading of between 22.375V and 23.625V. According to the aforementioned findings, X(100) is more than X(25), indicating that the error of a block measurement of 100V is substantially larger than that of a block measurement of 25V. As a result, when a multimeter measures various voltages, the mistakes caused by various ranges vary. The gear with the smallest measurement range should be chosen as much as feasible in the case of meeting the value of the signal to be measured. The measurement's precision is increased as a result.
(3) The mistake that results from using a multimeter's same range to measure two distinct voltages.
It can be seen that the maximum relative error of the measured voltages of 20V and 80V is significantly more than that of the latter. Therefore, whoever is nearer to the full scale value will have more accuracy when utilizing the same range of a multimeter to measure two distinct voltages. As a result, while measuring voltage, the voltage should be displayed over the range of the multimeter by at least 2/3. Only in this manner is it possible to lessen measurement error.
2. Range selection and electrical barrier measurement inaccuracy
Electrical resistance can be measured in ranges ranging from 0 to. An ohmmeter has a non-linear, uneven, and inverted scale. It is quantified as a percentage of the scale's arc length. Additionally, the "central resistance"—the multiplier of the central scale number by the scale's arc length—is the internal resistance of each range. The current flowing in the circuit is half of the full scale current when the measured resistance is equal to the center resistance of the chosen range. The scale's center is shown by the pointer. According to the following formula, it is accurate:
R%=100% (R/center resistance)...2
