Troubleshooting Tips for Digital Multimeters
Regarding the troubleshooting and troubleshooting skills of digital multimeters, you should first look for faults from the outside and then the inside, easy first and then difficult, break them into parts, and focus on breakthroughs, including sensory methods, voltage measurement methods, short circuit and open circuit methods, etc., repair skills for digital multimeters share.
1. Feeling method
Use your senses to directly judge the cause of the fault. Through visual inspection, you can find such things as broken wires, desoldering, short circuits, broken fuse tubes, burned components, mechanical damage, lifted and broken copper foil on printed circuits, etc. ;You can touch the temperature rise of batteries, resistors, transistors, and integrated blocks, and refer to the circuit diagram to find out the cause of abnormal temperature rise.
In addition, you can also use your hands to check whether the components are loose, whether the integrated circuit pins are firmly inserted, and whether the transfer switch is stuck; you can hear and smell whether there are any strange sounds and smells.
2. Voltage measurement method
Measuring whether the working voltage of each key point is normal can help you quickly find the fault point. Such as measuring the working voltage and reference voltage of the A/D converter.
3. Short circuit method
The short circuit method is generally used in the methods of checking A/D converters mentioned above. This method is often used when repairing weak current and microelectric instruments.
4.Circuit breaking method
Disconnect the suspicious part from the whole machine or unit circuit. If the fault disappears, it means that the fault is in the disconnected circuit. This method is mainly suitable for situations where there is a short circuit in the circuit.
5.Measurement of components
When the fault has been narrowed down to one location or a few components, it can be measured online or offline. If necessary, replace it with a good component. If the fault disappears, it means the component is bad.
6.Interference method
The human body induced voltage is used as an interference signal to observe the changes in the liquid crystal display. It is often used to check whether the input circuit and display part are intact.
Digital multimeter repair tips
For a faulty instrument, you should first check and determine whether the fault phenomenon is common (all functions cannot be measured) or individual (individual functions or individual ranges), and then differentiate the situation and solve it accordingly.
1. If all gears fail to work, focus on checking the power circuit and A/D converter circuit.
When checking the power supply part, you can remove the laminated battery, press the power switch, connect the positive test lead to the negative power supply of the meter under test, and connect the negative test lead to the positive power supply (for a digital multimeter). Turn the switch to the diode measurement position. If it displays is the forward voltage of the diode, it means that the power supply part is good. If the deviation is large, it means there is a problem with the power supply part.
If there is an open circuit, focus on checking the power switch and battery leads.
If a short circuit occurs, you need to use the circuit breaking method to gradually disconnect the components using power, focusing on checking the operational amplifier, timer, A/D converter, etc. If a short circuit occurs, generally more than one integrated component will be damaged.
