Main Difference – Analog vs. Digital Multimeter
A multimeter is a device which is used to make measurements such as voltage, current and resistance of an electrical circuit. The main difference between analog and digital multimeter is that the analog multimeter consists of a continuous scale over which a deflecting needle indicates the value to be measured, whereas, in digital multimeters, a digital display directly shows the value.
What is an Analog Multimeter
An analog multimeter is shown below:
To take a reading, firstly, the type of measurement (voltage, current, or resistance and whether the current is alternating or direct) and the expected range needs to be selected from the large dial below. Then, the leads (shown docked on the right) are placed at the relevant points on the circuit.
Central to the functioning of the analog multimeter is the D’Arsonval galvanometer. This consists of a coil carrying a current attached to a rotatable drum. Two permanent magnets are placed on either side of the coil. As current flows through the coil, a magnetic field forms around it. This magnetic field interacts with the magnetic field of the permanent magnet, so whenever the current flowing through the coil changes, the drum rotates. A needle is attached to the drum, which moves along the reading scale. An analog multimeter primarily measures current. Measurements of voltage and resistance are first converted to a corresponding current, which is then indicated by the needle.
What is a Digital Multimeter
A digital multimeter is essentially a voltmeter. In order to measure current and resistance, some internal circuitry is used to “convert” current and resistance values to corresponding voltage values. Then, using an analog to digital converter, the voltage is converted to a digital signal and a value is displayed using a display, which is typically a 7 segment display. The image below shows a digital multimeter:
In older digital multimeters, the type of measurement as well as the range needs to be selected manually. Most new digital multimeters have an auto ranging feature. However, users still have the ability to manually select the range (this is especially useful when measuring values that change by large amounts periodically).
Compared to an analog multimeter, digital multimeters need not be calibrated as often. In addition, the readings are more precise and there is no chance for parallax errors to occur when taking a reading. However, it is difficult to take an accurate reading when a digital multimeter is used to measure a value which is constantly fluctuating. The following video contains a comparison of the two types of multimeters and a discussion of their relative advantages:
Difference Between Analog and Digital Multimeter
Analog multimeter uses a printed, continuous scale. A needle moves along the scale to indicate a reading.
Digital multimeter uses a digital display.
Analog multimeter uses a galvanometer which primarily measures current.
Digital multimeter measures voltage using an analog to digital converter.
Sources of Error
Taking readings from an analog multimeter may produce parallax errors.
With a digital multimeter, it is difficult to determine an accurate average value when the reading is fluctuating.
Analog multimeters need to be calibrated often.
Digital multimeters may also require calibration. However, they do not need to be calibrated as often as analog ones.