DMM Aneng AN870

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The brand Aneng has been on a lot of meters recently (in 2017), most of them very capable meters at very good prices, do this trend continue with this meter?

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I got the meter in the usual black plastic bag with some protective wrapping around the pouch.

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The pouch.

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

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The probes has removable tip covers, the tip and tip cover has the usual CAT markings, but there is not much markings on the probe shafts.

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The shrouded plug is the slightly short variety.

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The DIY probe set, it is a bit low in quality and some work may be required to screw the tips in (One of the banana plugs was missing threads).

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A end without any tip.

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The DIY probes with the different tips.

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The thermocoupler is the probe type, this is useful for stuff where you want to stick the thermocoupler in, but not very good at measuring surface temperatures.


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The range switch is a bit difficult to use single handed when meter is on the tilting bale, it slides around.

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Display

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The above picture shows all the segments on the display, not all are used by this meter.
Notice the small 2, 20,200, 2000 digits, they are used to show the selected range.
The backlight has a hotspot at the minus sign, the rest of the display is fairly even illuminated.

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

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The NCV is the usual bars and the buzzer.



Functions

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Buttons: REL and MAX/MIN will change to manual range and return to auto range when disabled.

Rotary switch:
Input

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Measurements 1uF

A look at the capacity measurement waveform.

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Frequency input resistance depends on input voltage. This is fairly similar to mVAC input.

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The meter cannot be used at 20A, the reading will drift (At 19A 5% drift in 13 seconds). At 10A the drift is still present, but much slower.
AC input cannot handle large DC offset.



Tear down

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Four screws and the back could be removed.

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The circuit board is shaped to follow the box.

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6 small screws and the circuit board was nearly loose, I had to unsolder the backlight to get it out.

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The display and backlight are still in the box-

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The 20A shunt (R33: 0.01ohm) is very small, it is no wonder it cannot handle 20A without getting hot, or is it the copper trace. Sense is connected to the uA shunt (R23: 99ohm). The mA shunt (R24: 1ohm) is next to the uA shunt. On opposite side of the circuit board is the mAuA fuse and a transient diode (D5: 6V8) to protect the resistors until the fuse blows.
The 10Mohm input is done with two resistors (R29 & R30: 2x5Mohm) and goes directly to the chip. For the ohm, capacity, frequency and mV input the input goes to a PTC (PTC1: 1.5Kohm) and a transistor pair (Q3 & Q4).
The multimeter IC (IC3) has a external EEPROM (IC1: P24C02A) for calibration and functions, there is also a reference IC (Q5: ICL8069). There is a transistor for the buzzer (Q2) and for the backlight (Q1).
At the top of the circuit board is a trace as antenna for the NCV, it has some high ohmic resistors (R37, R38, R39: 3x20Mohm) as load.

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This side of the circuit board only has contact pads for the switches, range selector and LCD display. The 20A trace is also present in this side, but it is not enough for 20A.




Conclusion

The meter is within the specified tolerances (Except 20A range) and it has lot of functions and ranges, but the CAT rating is fake.
It is a fairly good meter to use on the bench.



Notes

The multimeter was supplied by Banggood for review.

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