DMM LAOA LA814103

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This is a small pocket DMM with voltage, ohms, capacity, frequency and current, i.e. basically all common multimeter functions.

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The meter was in a clamshell pack. On the back is a list of the main specifications.

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In the box was the meter and a manual in Chinese.

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Probes has same CAT rating as meter: CAT II 600V

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The range switch is easy to turn, the meter will not slide around. The detents on the range switch are a bit weak, i.e. it is possible to place the range switch between two ranges.

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It is possible to use the meter when it is inside the box, making it a bit splash proof.

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Display

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The above picture shows all the segments on the display.

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Typical display during usage, it will show the selected range and value.



Functions

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Buttons: Selection of Rel and Hz/duty will disable auto ranging and it stays disabled

Rotary switch:

Input

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This meter only have a red and black probe coming out, no other connections.


Measurements
1uF

Capacity measurement waveform for 1uF capacitor

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Frequency input resistance in frequency position.

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Frequency input resistance in Hz position.

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The meter is supposed to have a 4nF range, but I could not check it because the offset is 10nF. Capacity is easy within tolerances when using REL function.




Tear down

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I had to remove one screws, to open it, this is also required when replacing battery.

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The circuit board was mounted with four clips, it was not necessary to remove any screws.

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This meter requires a lot of adjustment from the factory (VR1..VR4: Trimpots). On the input side we have a PTC for protection in ohm and frequency ranges, the ohm sense input (R19: 900kOhm), the 10Mohm input (R26 & R28: 2x5Mohm). There is also 3 protection transistor pairs (Q1 & Q2, Q3 & Q4, Q5 & Q6). R19 uses Q3 & Q4 as protection. PTC uses Q5 & Q6 in ohms and Q1 & Q2 in frequency.
Current shunts (R16: 1ohm, R17: 99Ohm) are protected by diodes (D5, D6, D8, D9) and the large PTC (PPTC2).

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This side is without parts, but some stuff on the other side needs holes in the circuit board. This includes the springs for connecting the buzzer.

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Conclusion

The meter says CAT II 600V, if the range switch can handle 4000V without arching it may be correct.

The meter is well equipped with ranges for a pocket meter and can match many larger meters, precision is fairly good (Except low capacity range), safety looks decent for occasionally mains work at home.



Notes

This meter looks identical to the UNI-T UT120C (The circuit board is also marked with UT120C)

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