Multimeter are sometimes small, portable, battery-powered units. Larger ones are designed to sit on a countertop and are powered by a wall outlet. A multimeter can provide either a digital or an analog display. A digital display shows the readings as digits on an LCD (liquid crystal display) panel. A digital multimeter is sometimes called a DMM (digital multimeter) or a DVM (digital voltage meter). An analog display shows the readings as a needle moving across a scale of values.
Using A Multimeter
Before you begin to use a multimeter, you must tell it three things: (1) what you want it to measure (voltage, current, or resistance), (2) whether the current is AC or DC, and (3) what range of values it should expect. If you are measuring the voltage output from a wall outlet (110–120 V), the range should be much higher than when you are measuring the voltage output of a computer power supply (3–12 V). Setting the range high assures you that the meter can handle a large input without pegging the needle (exceeding the highest value the meter is designed to measure) or damaging the meter. However, if you set the range too high, you might not see the voltage register at all. Set the range low enough to ensure that the measure is as accurate as you need but not lower than the expected voltage. When you set the range too low on some digital multimeters, the meter reads OL on the display.
For example, to measure the voltage of house current, if you expect the voltage to be 115 volts, set the voltage range from 0 to somewhere between 120 and 130 volts. You want the high end of the range to be slightly higher than the expected voltage. To protect themselves, most meters do not allow a very large voltage or current into the meter when the range is set low. Some multimeters are autorange meters, which sense the quantity of input and set the range accordingly.
A meter comes with two test probes. One is usually red and the other black. Install the red probe at the positive (+) jack on the meter and the black probe at the negative (-) jack.
Caution In Use A Multimeter
- Improper use of this meter can cause damage, shock, injury or death. Read and understand this user manual before operating the meter.
- Always remove the test leads before replacing the battery or fuses.
- Inspect the condition of the test leads and the meter itself for any damage before operating the meter. Repair or replace any damage before use.
- Use great care when making measurements if the voltages are greater than 25VAC rms or 35VDC. These voltages are considered a shock hazard.
- Warning! This is a class A equipment. This equipment can cause interferences in the living quarters; in this case the operator can be required to carry out adequate measures.
- Always discharge capacitors and remove power from the device under test before performing Diode, Resistance or Continuity tests.
- Voltage checks on electrical outlets can be difficult and misleading because of the uncertainty of connection to the recessed electrical contacts. Other means should be used to ensure that the terminals are not “live”.
- If the equipment is used in a manner not specified by the manufacturer, the protection provided by the equipment may be impaired.
- This device is not a toy and must not reach children’s hands. It contains hazardous objects as well as small parts that the children could swallow. In case a child swallows any of them, please contact a physician immediately
- Do not leave batteries and packing material lying around unattended; they can be dangerous for children if they use them as toys
- In case the device is going to be unused for an extended period of time, remove the batteries to prevent them from training
- Expired or damaged batteries can cause cauterization on contact with the skin. Always, therefore, use suitable hand gloves in such cases
- See that the batteries are not short-circuited. Do not throw batteries into the fire.
How to Choose Multimeters : Digital Multimeter Vs. Analog Multimeter
An analog multimeter is designed on a micrometer, and its needle moves along a scale calibration to make various measurements. Analog multimeters are great for the measurement of voltage, current, resistance, frequency and signal power. Switched-range analog multimeters are relatively cost-effective but not user-friendly. Also, reading resistance scales on an analog multimeter is difficult to those lacking experience. When used as an ammeter, this multimeter exhibits extremely low resistance and high sensitivity with scales down to 50 µA.
Advantages over the digital multimeters
Though some users denounce the analog multimeters as obsolete, yet these too have their advantages over the digital multimeters. For example checking diode using analog multimeter is more accurate than using a digital multimeter. Again, short circuit problems can be found using the analogue multimeter with a better output. Just like its digital version, most of the advanced versions of an analog multimeter have great features like capacitor, diode and IC testing modes.
Typically, a digital multimeter displays digits, though some may also consist of a liquid crystal display bar representing the quantity measured. A common tool for measuring voltage, the digital multimeter is a preferred voltmeter because of its higher resistance of 1 M or 10 M as against 200 in an analog multimeter on a similar range. To be able to obtain accurate readings, the resistance of the meter must be minimum ten times the resistance of the circuit.
Advantages over the analog multimeters
The best part about digital multimeters is that they give more accurate measurements compared to its analog counterpart. And the accuracy is not just restricted to giving correct results. While analog multimeters indicate the value with a needle over a scale, digital Multimeters has a LED or LCD display, which can display output in as a digital numerical feed even up to decimal points. This makes it very specific and also readable. Apart from that it also has can be adjusted whenever required to measure in ohm, ampere and volt.
Example Analog Multimeter
Example Digital Multimeter
Multimeter is equipment that must be owned by electronics technician, so choose multimeter according to the needs.