Digital Multi meter:

A digital multimeter or DMM is one of the most widely used pieces of test equipment today. DMMs are available very cheaply and these digital multimeters can provide very high degrees of accuracy when measuring the parameters within an electronics or electrical circuit. As a result,A Digital multimeter can be a hand-held device useful for basic fault finding and field service work or a bench instrument which can measure to a very high degree of accuracy. They can be used to troubleshoot electrical problems in a wide array of industrial and household devices such as batteries, motor controls, appliances, power supplies, and wiring systems.

Purpose:

A typical multimeter may include features such as the ability to measure voltage, current and resistance.

How to Use DMM:


When using the meter it is possible to follow a number of simple steps:
1. Turn the meter on
2. Insert the probes into the correct connections - this is required because there may be a number of different connections that can be used.
3. Set switch to the correct measurement type and range for the measurement to be made. When selecting the range, ensure that the maximum range is above that anticipated. The range on the DMM can then be reduced as necessary. However by selecting a range that is too high, it prevents the meter being overloaded.
4. Optimise the range for the best reading. If possible enable all the leading digits to not read zero, and in this way the greatest number of significant digits can be read.
5. Once the reading is complete, it is a wise precaution to place the probes into the voltage measurement sockets and turn the range to maximum voltage. In this way if the meter is accidentally connected without thought for the range used, there is little chance of damage to the meter. This may not be true if it left set for a current reading, and the meter is accidentally connected across a high voltage point!

Measuring Current:

1. Insert the probes into the correct connections - in many meters there are a number of different connections for the probes. Often one labelled common into which the black probe is normally placed. The other probe should be entered into the correct socket for the current measurement to be made. Sometimes there is a special connection for current measurements, and sometimes a separate one for either low or high current measurements. Select the correct one for the current measurement to be made.
2. Set main selector switch on the meter switch to the correct measurement type, (i.e. current) and range for the measurement to be made. When selecting the range, ensure that the maximum range is above the expected reading anticipated. The range on the DMM can then be reduced as necessary. However by selecting a range that is too high, it prevents the meter being overloaded.
3. When the measuring the current, optimise the range for the best reading. If possible enable all the leading digits to not read zero, and in this way the greatest number of significant digits can be read.
4. Once the reading is complete, it is a wise precaution to place the probes into the voltage measurement sockets and turn the range to maximum voltage. In this way if the meter is accidentally connected without thought for the range used, there is little chance of damage to the meter. This may not be true if it left set for a current reading, and the meter is accidentally connected across a high voltage point!


Measuring Resistance:

There are a few simple steps required to make a resistance measurement with a digital multimeter:
1. Select the item to be measured: This may be anything where the resistance needs to be measured and estimate what the resistance may be.
2. Insert the probes into the required sockets Often a digital multimeter will have several sockets for the test probes. Insert these or check they are already in the correct sockets. Typically these might be labelled COM for common and the other where the ohms sign is visible. This is normally combined with the voltage measurement socket.
3. Turn on the multimeter
4. Select the required range The digital multimeter needs on and the required range selected. The range selected should be such that the best reading can be obtained. Normally the multimeter function switch will be labelled with the maximum resistance reading. Choose the one where the estimated value of resistance will be under but close to the maximum of the range. In this way the most accurate resistance measurement can be made.
5. Make the measurement With the multimeter ready to make the measurement the probes can be applied to the item that needs to be measured. The range can be adjusted if necessary.
6. Turn off the multimeter Once the resistance measurement has been made, the multimeter can be turned off to preserve the batteries. It is also wise to turn the function switch to a high voltage range. In this way if the multimeter is used to again for another type of reading then no damage will be caused if it is inadvertently used without selecting the correct range and function.