Checks before measurement with a multimeter
A multimeter is a multi-functional, multi-range measuring instrument that is indispensable in electronic and electrical technology. Generally, multimeters can measure DC current, DC voltage, AC current, AC voltage, resistance and audio level. Some can also measure capacitance, inductance and some parameters of semiconductors (such as β). If simply distinguished by display mode, multimeters can be divided into analog multimeters and digital multimeters.
The three basic functions of a multimeter are to measure resistance, voltage, and current, so the old-timers call it a three-purpose meter. Today's multimeters have added many new functions, especially digital multimeters, such as measuring capacitance value, transistor amplification, diode voltage drop, etc. There is also a talking digital multimeter that can broadcast the measurement results in language.
Steps
Check whether the battery voltage and power generation are normal and whether the battery pile head is severely rusted. Many car owners think that the result of leakage is a battery problem or a generator problem;
Remove the negative terminal of the battery, set the multimeter to the maximum current setting, connect the red test lead to the negative wire, and connect the black test lead to the battery pile head and secure it;
Turn off all electrical appliances inside and outside the car, lock the door, observe the current, adjust it to the appropriate gear, and record it;
Wait for about 20 minutes; after all modules of the vehicle enter the sleep state, read the accurate static discharge current;
The quiescent current is generally 0.03A (i.e. 30mA), please refer to the maintenance manual for details, and it does not exceed 50mA;
If the quiescent current is too large (as shown in the picture above), we can check by pulling out the fuses and relays, that is, pulling out the fuses one by one and observing the size of the quiescent current;
Check before measurement
Observe whether the multimeter needle is set to 0. If it is not at 0 position, turn the zero adjustment screw to set it to 0 position.
Check the integrity of the two test leads and leads. This is particularly critical when measuring higher AC voltages to prevent electric shock accidents.
Check the lead plug and tighten it if it is loose. Sometimes the looseness is caused by the loosening of the fastening nut of the jack. At this time, the watch case must be repaired.
