DMM XB-866

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This is a cheap pocket DMM, it has the most common ranges, but do not have any functions.

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The meter arrived in a cardboard box that is designed for two models (The two sides are different models).

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The box contained the meter and a manual.

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The probes are part of the meter and cannot be replaced without soldering.

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The area around the batteries, the spring and lid is a bit cramped, making the lid a bit difficult to mount and unmount.



Display

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The above picture shows all the segments on the display, not all are used on this meter.

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Typical display during usage, it will show the number and what range is selected.



Functions

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Buttons: Rotary switch:

Input

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A red and a black probe is linked to the meter.



Measurements
DMMschema

mVAC must be manually selected.



Tear down

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Removing the battery lid also loosens the back and it can be removed, together with the lid.

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Four more screws and I could remove the circuit board, I had to be a bit careful with the battery connections.
The display do not have tight alignment control, this makes it a bit tricky to get the display/zebra stipe correctly aligned when putting it together again.

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Only the switch, buttons and LCD connections on this side.

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The green device (R36) is a PTC for input protection, the two resistors near it, but under the buzzer is the current shunts for uA and mA. The input voltage resistor is split in two (R2, R3: 2x5Mohm). The input clamp on this meter is probably D2 & D3. The meter has two trimpot for adjustment. Usual meters uses a crystal to get a stable frequency for the DMM chip, but in this case it is a resonator (It is cheaper).
It looks like the fuse is the first part on the input, i.e. a blown fuse prevents measuring voltage!

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Having the probe leds through a hole in the circuit board will improve the strength considerable.

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Conclusion

The meter is very small, but has many of the common ranges (Autorange helps with that). It works fine in the ranges it has and for a simple meter it is fairly good, but do not blow the fuse, it is soldered in.



Notes

This meter exist with many different names on it and small variations in functions.

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