DMM BSide ZT302

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This is a cheap DMM with all common function.

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The meter arrived in a fairly anonymous multimeter box, but the checked illustration on the back matches the meter.

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It included the DMM, a pair of probes and a manual.

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The probes has removable tip covers, but is only rated for CAT-II, even with the covers on.

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The plug is fully shrouded, but is slightly smaller than standard probe plug size.

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When using the tilting bale the meter is nearly stable enough to turn the switch, but the meter is very smooth and will easily slide around.

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Display

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

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Typical display during usage, it will show the number and what measurement is selected.
The current software version has a bug, in manual ranging the manual annotation will disappear when using the range button.


Functions

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Buttons: Rotary switch:
Input

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Standard probes cannot be fully seated in the terminals, but they will make contact. Banana plugs fits perfectly.



Measurements 1uF

A look at the capacity measurement waveform.

50Hz

50Hz square wave

5kHz

5Khz square wave

5kHz2.6kohm

Loaded with 2.6kOhm gives half output, i.e. impedance is 2.6kOhm.

50Hz2.6kohm

And it has a capacitor in the output.

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Frequency input impedance.

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The 10A range is not stable near full current (Technically this is a A range, not a 10A range).



Tear down

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Four screws and the back could be removed with some difficulties.

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As usual the circuit board is made to fit in the box, there is also some clips to hold it in.

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3 screws and I could remove it.

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Two more screws and the display could be removed.

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This side of the circuit board only contains the switch, button and display pads, no components here.

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All electronic is on this side. The uA shunt (R23+R24: 99ohm+1ohm) with protection diode (D5) and the 200mA fuse. The voltage input with two resistors (R29, R30: 5Mohm+5Mohm). The ohm protection (PTC1, Q3, Q4). The reference (Q5: ICL8069). Transistors for switching buzzer (Q2) and backlight (Q1) on. The EEPROM (IC1: 24C02) and the multimeter IC as a COP.

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Conclusion

As usual I am very doubtful about the CAT rating, it must surview full voltage on the ampere input, but they are not rated for that, neither are the fuses.
The meter has many ranges but are missing a bit in the ampere (It has the resistor for the missing ranges), but due to the way this meter is designed it is ideal for measuring current in the 100mA to 1A range with very low burden voltage.
The meter can do min/max, test leds and the backlight do not turns off after 15 seconds.

It will call it acceptable DMM for hobby use, but keep it away from anything with mains voltage and lots of amps.



Notes

This meter exist with many different names on it and small variations in functions.
Check the Aneng AN8008 meter for a smaller version of this meter.

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