Discussion About Multimeter
1. When we want to measure voltage reading, the multimeter must be parallel with the component that we want to measured. The red on the high voltage side, and black on the lower. When measuring current, amperes, the multimeter must be in series with the component. Remove one side of the component and connect the black multimeter lead to the board where the component was plugged in and the red lead connects to the loose component.
The difference between the two is that if we measure the voltage, the internal resistance of the multimeter is set to what is essentially infinity. If it was anything less then it would be acting as a resistor and drawing its own current which would reduce the current on the component being tested, which would in turn reduce the voltage reading we get.
When we measured current, the internal resistance of the multimeter is set to almost 0. This is to ensure that it does not contribute to the resistance of the series it is in. Increasing the resistance of a series of components can cause current further “upstream” to flow into other branches which throws off our current reading.In short, for voltage tests the mm is placed in parallel with the components and acts as an open line to take a reading. For current readings the multimeter is placed in series with the component and it acts as a simple piece of wire with zero resistance.
2. There are many types of errors that maybe encountered in the measurement process and measures to minimize it. For examples random error, systematic error and gross error are static error
(i) random errors
Random errors are ones that are easier to deal with because they cause the measurements to fluctuate around the true value. If we are trying to measure some parameter X, greater random errors cause a greater dispersion of values, but the mean of X still represents the true value for that instrument.
(ii) systematic error
A systematic error can be more tricky to track down and is often unknown. This error is often called a bias in the measurement. In chemistry a teacher tells the student to read the volume of liquid in a graduated cylinder by looking at the meniscus. A student may make an error by reading the volume by looking at the liquid level near the edge of the glass. Thus this student will always be off by a certain amount for every reading he makes. Systematic error can be classed by three different error such as: -instrument error
(iii) gross error
Gross error is usually made by human mistakes. As example, error when taking measurement reading, incorrect recording and improper use of instrumentation. We can minimize this error by taking at least three separate readings and take proper care in reading and recording.
3. The significance of using the correct range for measurement are to get the more accurate and precise reading and to reduce the percentage of error when taking a reading.