Precautions for Measuring Direct Current with a Multimeter
Mechanical Zero Adjustment:
First, perform mechanical zero adjustment on the multimeter to ensure accurate measurements.
Select the Appropriate Range:
Choose a suitable range for the measurement. This helps to obtain accurate readings and prevent damage to the multimeter.
Connect the Multimeter in Series for Current Measurement:
When using the current - measuring function of the multimeter to measure direct current, connect the multimeter in series with the circuit being measured. Only by connecting in series can the current flowing through the ammeter be the same as the current in the measured branch.
To measure, break the measured branch and connect the red and black test leads of the multimeter in series between the two broken points.
It is extremely important to note that the ammeter should never be connected in parallel to the measured circuit. Doing so is very dangerous and can easily burn out the multimeter.
Pay Attention to the Polarity of the Measured Quantity:
Ensure that you correctly identify the positive and negative polarities of the direct - current being measured. Connect the red test lead to the positive terminal and the black test lead to the negative terminal.
Read the Scale Correctly:
Familiarize yourself with the scale of the multimeter and read the measurement values accurately.
Using the 2.5A DC Current Range:
When selecting the 2.5A DC current range, insert the red test lead into the 2.5A measurement jack. The range switch can be set to any position within the DC current range.
Extending the Range beyond 2.5A:
If the measured direct current is greater than 2.5A, you can extend the 2.5A range to a 5A range. The method is simple: connect a 0.24 - ohm resistor between the "2.5A" jack and the black test - lead jack. This effectively converts the range to a 5A current range.
The 0.24 - ohm resistor used should be a wire - wound resistor with a power rating of at least 2W. A resistor with too low a power rating may burn out.
