Using your Ohm Meter

Manual adjust meter (left) -- Auto ranging meter (right)

Manual adjust meter and auto ranging meter

Setting your meter up for testing

When checking the resistance of a component, the meter leads may be connected in either direction. Some components may contain a diode which will require making a connection in a specific way. If this is the case, you will be directed in our instructions as to the correct lead connection.

If you are using an auto ranging meter similar to the right meter, place the selector in the “Ohm” or “?” position.

If you have a manual adjust meter similar to the left meter, set the selector to the lowest position, or the “200” scale to begin. After connecting the leads of your meter to the part, the manual adjust meter may need to be adjusted to the proper scale. Move the selector up to the 2k, 20k or 200k scale until you have a resistance value that is readable and the numbers hold relatively steady.

When measuring a component with a very low resistance value, such as the primary winding of an ignition coil, you must factor in the slight default resistance that your meter may have. Before making a connection to the test subject, connect the leads of your meter together. An auto ranging meter may have a “Zero” button; press the button with the leads connected together. The meter reading should go to zero ohms. If your meter does not have a “Zero” button, you will need to subtract the default resistance from the value recorded when performing your component test.

As an example, let’s say you are measuring the primary resistance of an ignition coil. When you have connected your leads together you recorded 0.2 ohms of resistance. When you connect your meter leads to the primary coil connectors your meter reads 0.8 ohms. You must subtract the 0.2 ohms from the 0.8 ohms recorded during the test. The true ignition coil primary resistance value is 0.6 ohms, (0.8 – 0.2 = 0.6).

Understanding your meter readings

Whether you are using an auto ranging meter or a manual adjustment meter for testing, the reading may appear similar to this; (example: .826 k). A meter value with a “k” following the number will require a conversion to a whole number. The “k” symbol stands for 1,000. To convert the reading to a whole number, change the decimal point to a comma. Using our example provided, moving the decimal point three spaces right, the whole number becomes 826.00, or 826 ohms of resistance on the circuit. Let’s try one more example; convert the meter reading of 1.026k to a whole number. By following the rules and changing the decimal point to a comma, the reading becomes 1,026.00, or 1,026 ohms of resistance.

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