What each digit on a digital multimeter means
Misconceptions regarding the choice of automobile multimeters
Multimeters are necessary for practically every business because they are a testing tool that is frequently utilized in the maintenance sector. The multimeters that many businesses use might not, however, be enough for their demands.
1. Emphasis on functional variety while ignoring accessory symmetry
When making a purchase, some consumers tend to focus more on the variety of multimeter functions than on how well the accessories match. The diversity of functions cannot be realized organically without the required accessories. For instance, some users acquire a multimeter in the hopes that it will be able to detect the starting current and the temperature under a variety of circumstances, but they skip out on purchasing particular current clamps and thermometer probes. The proper syncing of some accessories is essential if you want a car multimeter to perform to its best potential. Many of these accessories are compatible with the relevant features of the automobile multimeter, and some of them are necessities.
Inductive pick-ups, battery alligator clips, special test clips for SMD patch components (used to test parameters like SMD resistance, capacitance, inductance, and transistors, which can be operated with one hand, making Measurement more convenient), current sensors, pressure probes, torque probes, and IC probes are among the accessories that are typically included in a car multimeter. In general, maintenance uses these items less frequently. When acquiring accessories, maintenance firms should take into account a number of factors, including the user's technical proficiency, the maintenance company's financial situation, and daily use, in order to make the best decision and get the most out of the equipment.
2. Discard quality tools because to uncomplicated language hurdles
Some consumers desire to purchase imported auto multimeters, but when they learn that the interface is in English, they quickly give up on those with less functional or more functional items. In actuality, this is not required. It is not difficult to use because the fundamental functions of different multimeters are comparable and many functions are designated with standard symbols. You can quickly master the way of use if you conduct a brief research.
Multimeters are generally not idle, but many functions are not fully utilized in maintenance.
1. "Give up on choking" for some functions
Some maintenance personnel are often afraid to use a multimeter because they are worried about damaging the equipment during the test, the most obvious one is the current test. The current test method is not complicated, such as the starting current, the primary and secondary current of the ignition coil, and the current test of the fuel injector, many fault clues can be found as a basis for diagnosis, but technicians rarely use it in maintenance. It is understood that many repairmen are afraid to use the current test function because they are afraid of "burning the meter" or damaging the components under test due to misoperation of the test. In fact, many multimeters are designed with special circuit devices or mechanical protection devices in order to protect integrated circuits. For example, one more DY2201 multimeter adopts a mechanical protection device for the current measurement jack to prevent misuse. Only when current measurement is selected, the corresponding "mA" or "20A" jack will be opened. Otherwise, it will be blocked by the baffle, which can effectively avoid inserting the wrong test leads. Maintenance personnel can boldly use the current test function, but must operate in accordance with the use process.
2. Insufficient emphasis on errors in testing
Any instrument will have errors in the measurement, but the errors should be minimized in the measurement to avoid operating errors to ensure the accuracy of the measurement results. The large errors that often occur in the use of multimeters are sometimes caused by instruments, and sometimes caused by some human factors. The following two aspects need to attract the attention of maintenance personnel: ①Because the accuracy and resolution of the multimeter are not enough, if the judgment is only based on estimation, it will often lead to human error. ②Due to the different test methods of various multimeters, the multimeters will have their own instrument errors in different signal tests. Therefore, when using multimeters, maintenance personnel should try to use instruments with high precision levels, and at the same time strictly follow the operating procedures. reduce the error.
Some functions of the multimeter are rarely used in maintenance, or their functions have not been fully utilized by users.
1. The current test function has not been paid attention to
For a long time, the current test function has been neglected in maintenance. With the emergence of more and more new technical equipment on the car, sometimes it is impossible to carry out effective diagnosis without current test. For some leakage situations that are difficult to judge, such as: ①The battery plates are short-circuited or oxidized and fall off, resulting in self-discharge and power loss. ②Electronic components are grounded to cause leakage, such as the insulation layer of a certain line in the circuit is aging or falling off, resulting in contact with other metal parts. In these cases, the multimeter's current test function can come in handy.
(1) Leakage test method
When performing leakage test, you need to use a multimeter. The specific method is as follows: turn off all electrical equipment on the car, remove the ignition key, and use the current clamp attached to the car multimeter. If the current flowing through the meter is 10-30mA, it means that the car has no leakage. Conversely, if the display is too large, it is considered that there is a body leakage fault. It should be noted that some systems still need to absorb a lot of power within 15 minutes of turning off the ignition switch, so if the measured current is above 50mA, it should be tested after 15 minutes. If it is still above 50mA at this time, it means that there is a discharge phenomenon, and further diagnosis is required. In the case of confirming that there is leakage in the body, keep the current clamp clamping the negative pole of the battery all the time, and you can remove the fuses one by one while observing the change of the current value of the meter. If the number displayed on the meter does not change after a certain fuse is removed, it means that the leakage does not occur in the circuit. If the digital clamp ammeter shows that the value returns to normal 10-30mA (the normal value of some cars is below 50mA, the specific value is related to the model), it means that the leakage phenomenon has been eliminated, which means that the fuse control circuit has leakage, grounding or short circuit problems exist.
(2) Rapid diagnosis of electrical equipment
Using the current test function, you can also quickly diagnose and detect the reasons why many electrical equipment on the car, such as headlights, audio, oil pump relays, motors for electric doors and windows, and generators, do not work. For example, for the detection of electric fuel pump, if the working current I=4.5A, the fuel pump is working normally, if there is a fuel cut-off, it is caused by poor circuit connection; if the working current I<4.5A, it means that there is resistance in the circuit or The connection is bad, or the fuel tank is too dirty, and impurities block the oil filter, and the oil pump cannot absorb oil, resulting in no-load current; if the operating current I>4.5A, it means that the fuel filter may be blocked or partially blocked, resulting in an increase in the load of the oil pump . In this case, misjudgment of the oil pump is very easy to occur, and attention should be paid to it during the detection.
