DMM Zeast 282

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This is a fairly cheap DMM with 20000 count display.

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It arrived in a universal DMM cardboard box, the illustration do not match the meter.

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It included the DMM, a pair of probes, a thermocoupler and a manual.
The manual is without branding, it only says 20000 count DMM

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No tip covers on these probes that is rated for 1000V Cat III and 10A
This means the rating is wrong.

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The plug is fully shrouded, but shorter than standard probes.

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The thermocoupler is the typical cheap construction.

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The polarity markings for the battery is not very easy to see, there is a small + and - symbol at the bottom of the battery box.



Display

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The above picture shows all the segments on the display.
It has two readouts and a bargraph at the bottom.

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During AC Voltage or current the secondary readout will show frequency.

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Typical display on other ranges.

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Voltage detector shows dashes depending on the stregnth of the electric field.



Functions

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Buttons:
Rotary switch:


Input

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Measurements
1uF

A look at the capacity measurement waveform.

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The AC tolerance is a bit misleading, 0.06% is only 12 count at 20000, i.e. the count is the significant factor here.
The meter is easily within the specified tolerances and in many cases only one or two count out.


Tear down

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I had to remove four screws to open the DMM.

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And 6 more to take the circuit board out.

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This is where all the stuff are:
Two ceramic fuses, but only rated for 250V and 380V in a 600V rated DMM, oops. The 10A fuse has 100kA printed on it, but I doubt it.
The two resistors besides the 10A fuse is the mA and uA shunts (1ohm & 100ohm), the wire (R58: 0.01ohm) is the 10A shunt.
Beside the "thin" fuse is two diodes, they protect the mA & uA shunt in overcurrent conditions until the fuse blows.
The four resistors (R61, R62, R63, R64: 2.5Mohm) are the input resistor for voltage, creepage distance is rather low.
There is a 3.3V voltage regulator (IC6: HT7133 on circuit board), and two clamp transistors (Q5, Q6: 8050) near a PTC (Green part), that is the input protection.
THe main multimeter IC (IC7: HY12P65 on the circuit board) is rated for 5000 count, either the text on the circuit board is wrong or the other IC (IC4) is helping it to get better resolution. The 8 pin chip between them is a EEPROM to store calibration. There is also a 3 pin reference (DZ2: IC385 1.2V reference).

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On the front is only the range switch, the buttons and the lcd display.

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On this side the light for the LCD display can be seen.

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Conclusion

As usual on cheap(er) DMM's the CAT rating is wrong, the manual says not to use more than 36V DC on current terminals.
Because the mA range only goes to 200mA the burden voltage is not that bad and it has a A range with even lower burden voltage that has more than enough resolution for higher mA. With this DMM the battery must be replaced when the battery symbol shows or there is a risk of wrong readings.
The meter has all the common functions for a multimeter with exception of min/max (It has peak instead). The NCV, dual display and bargraph are nice additions. There is some precision behind the higher resolution at least in VDC, ohms do also look very good.



Notes

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

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