The Application of Fluke Multimeter in Automotive Maintenance
The most commonly used automotive electrical maintenance tool may be a multimeter. A typical multimeter can test voltage, current, and resistance. Specially developed multimeters, such as Fluke's F78/F88/F98, have many functions specifically designed for automotive testing, such as frequency, duty cycle, diode testing, temperature, dwell time (Dwell), and even engine speed (using accessories).
This material introduces how to use high-quality specialized multimeters and their accessories like Fluke for automotive maintenance. The analog/digital combination of this type of meter has a completely different advantage from other meters, and its accessories make maintenance more convenient and easy. Although using a multimeter to repair cars has a history of many years, most of them do not have specialized functions for car maintenance. Computers and various sensors are widely used in cars today, and a truly multifunctional multimeter is needed for car maintenance. The input impedance of analog (pointer) multimeters used in the early days was too low, which had a significant impact on electronic circuits during measurement. When testing resistance with this type of meter, a voltage of 9V is mostly used, so it is easy to damage sensitive electronic components. In recent years, new digital multimeters (DMMs) have been widely adopted.
Its input impedance is high, and its accuracy and performance are superior to analog meters. The voltage during resistance measurement is also low (usually 5V, Fluke is 3.5V), so it will not damage the components of each sensor. But there is also an issue with the number table. It cannot display information on the increase or decrease in measurement readings. During exhaust emission testing and engine analysis, it is found that a pure digital meter cannot provide stable variation values.
Fluke overcame the shortcomings of digital meters and replaced them with analog/digital combination meters. It has both the advantages of a digital meter and the advantages of an analog meter for dynamic measurement.
Considerations for fault diagnosis
When searching for faults in the electrical parts of a car, the important thing is the reasoning process of the cause of the fault. This process is very important. This is because you cannot see the internal situation and cannot dismantle a large number of components like mechanical components. By utilizing logic and reasonable steps, problems can be quickly identified. The key tool in this process is the multimeter.
The class nature of signals
The tested signals mainly include voltage, current, and resistance. But voltage is commonly used. The issues involved include: Is there voltage present? What is the voltage value? What should be the normal value? What is the voltage drop of the component or connection point? For example, if the input voltage of a relay is 12.8V and the output terminal is 9.2V, the voltage drop is 3.6V. Please note that the joints of the wires should be considered as components and will generate voltage drops. So it may also cause malfunctions.
