Test/review of DMM Aneng V8

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HKJ
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Test/review of DMM Aneng V8

DMM Aneng V8
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This is a cheap DMM with all common function.
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The box for the meter is designed for both the V7 and V8 meter.
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Inside the box is a pouch with everything in it, except the manual.
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The package included the DMM, a pair of standard probes, the universal probes, a thermocoupler and a manual in addition to the pouch.
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The probes are unbranded, has removable tip covers and is rated for CAT II 1000V, to CAT IV 600V
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The plug is shrouded.
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The thermocoupler is designed for insertion into stuff and is with a dual banana plug connector.
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The universal probes can be assembled to many different configuration, they are not high quality, but very useful.
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When using the tilting bale it is possible to turn the switch, but not use the buttons with one hand.
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Display
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All the segments on the display. There is both bargraph and secondary display
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Typical screen during usage with bargraph.
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In AC modes the secondary display is used for frequency.
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The NCV mode shows the usual EF (Electric field) on the display and change to bars when a actual field is detected. The led below the display will flash red and the buzzer will also sound.
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In temperature mode it shows both Celsius and Fahrenheit at the same time.
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Between the buttons is a led that will show red in continuity and NCV mode.
Secondary display functions, value after / is secondary value:
VAC: VAC/frequency, frequency/duty-cycle
Frequency: frequency/duty-cycle
Current: DCA, ACA/frequency, frequency/duty-cycle
Temperature: Celsius/Fahrenheit
Functions
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Buttons:


  • Range: Select and change manual range (Used in auto range position), hold down to return to auto range.
  • V.F.C.: Apply a high pass filter to AC voltage, it will also lock the range to 750VAC.
  • Select (Yellow): Select the ranges printed with yellow.
  • Rel: Shows values relative to current value, will also select manual range. Press again to disable. Hold down for flashlight.
  • Max/min: Starts recording maximum and minimum value, press to select between max/min, hold down to disable
  • Hold (Blue): Freezes the display reading.

Rotary switch:

  • Off: Meter is turned off
  • NCV: Non Contact voltage or electric field detection.
  • SquareOut: Frequency output from 50Hz to 5000Hz, use SELECT to step the frequency.
  • batt12V: 12V battery test
  • batt9V: 9V battery test
  • batt1.5V: 1.5V battery test.
  • 6 x ohm: Manual ohm ranges.
  • 3 x VAC: Manual VAC ranges
  • 4 x VDC: Manual VDC ranges.
  • °F °C: Temperature range.
  • uA: Micro ampere DC and AC with frequency and duty cycle for AC
  • mA: Milli ampere DC and AC with frequency and duty cycle for AC
  • A: Ampere DC and AC with frequency and duty cycle for AC
  • cont: Continuity
  • diode: Diode
  • C: Capacitance
  • ohm: Resistance
  • mVDC: Millivolt DC
  • mVAC: Millivolt AC with frequency and duty cycle.
  • VDC: Volt DC
  • VAC: Volt AC with frequency and duty cycle.

Input
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  • 20A: High current, it can only withstand 10+ ampere for a short time (Fuse is 10A).
  • mAuA: The lower current ranges, the selector switch will change between two different shunts (Fuse is 600mA).
  • COM: The common terminal for all ranges.
  • xxx: All other ranges.

The terminals fairly retracted into the meter.
Measurements

  • Volt and frequency

    • At 100mVrms input frequency input range is from 1.1Hz to 6MHz
    • At 1Vrms input frequency on VAC range is from 1Hz to 40kHz
    • Frequency input requires a zero crossing on both logic and VAC input
    • Duty cycle works from 2% to above 99% at 100kHz with 1Vpp, precision is within 0.2
    • 1 VAC is 5% down at 1.9kHz (RMS will not work at the frequency), AUTO and manual is similar.
    • 7 VAC is 5% down at 500Hz with VFC (RMS will not work at the frequency), AUTO and manual is similar.
    • When using VFC the range is locked to 750VAC, it cannot be select in manual voltage ranges.
    • Max/min needs less than 200ms to capture a voltage, but need many pulses for it.
    • Input impedance is between 10 and 11Mohm on DC and AC
    • Input impedance is high on mVDC (AC is limited to 10Mohm) and will drop to a few kOhm above 2V.

  • Current

    • 20A range will give audible alarm at 10A
    • Overload protection in uA and mA: 0.8A/250V 5×20mm ceramic fuse
    • Overload protection in A: 20A/250V 6×30mm ceramic fuse and 20A/250V fuse.

  • Ohm, Continuity, diode and capacitance

    • Ohm needs about 1.8s to measure 100ohm in auto range and 0.7s in manual range
    • Ohm is 1.0V open and 0.38mA shorted
    • Continuity is quick (Below 30ms).
    • Continuity beeps when resistance is below 50ohm.
    • Continuity is 1.0V open and 0.38mA shorted
    • Diode range uses 3.2V, max. display is 3.000V at 0.12mA, max. current is 1.6mA shorted
    • 10uF takes about 5 seconds to measure.
    • 11000uF takes about 10 seconds to measure.
    • No overload protection is rated.

  • Miscellaneous

    • 12V battery test uses a 1200ohm resistor
    • 9V battery test uses a 910ohm resistor
    • 1.5V battery test uses a 150ohm resistor
    • Frequency output has the following frequencies: 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000Hz
    • Current consumption of meter is 26mA (With backlight it is 29mA).
    • Meter works down to 2.4V where it turns off, battery symbol show at 2.9V.
    • Reading is stable within a few counts until it turns off.
    • Backlight fades slowly with falling voltage, display is nearly unreadable at 2.5V
    • The meter usual need a couple of display update to reach the final value.
    • Viewing angle is good, except from the top.
    • Display updates around 3 times/sec
    • Flashlight do not turn automatic off, but will turn off when the meter turns off.
    • Will automatic turn power off in about 15 minutes.
    • Standard probes can nearly be pushed fully down.
    • Weight is 416g without accessories, but with rubber sleeve and batteries.
    • Size is 176 × 91 × 47mm with rubber sleeve.

  • Probes

    • Standard probe resistance 40mOhm for one.
    • Standard probe wire is 79cm long.
    • Custom probe resistance is 56mOhm
    • Custom probe wire is 86cm long


1uF
A look at the capacitance measurement waveform.
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50Hz frequency output, it swings around zero.
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5000Hz frequency output.
freq50Hz100kOhm
50Hz output loaded with 100kohm halved the output voltage
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5000Hz output with 100kOhm load.
DMMInputVoltageSweepHz
Frequency input resistance depends on input voltage.
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The mVDC range is high impedance, until the protection clamps, mVAC is limited to 10Mohm.
DMMschema
Tear down
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I had to remove four small screws to open the meter.
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And 6 more to remove the circuit board.
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The range switch has 7 connections.
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All the electronic is on this side. The uA shunt (R16: 99ohm) is in series with the mA shunt (R15: 1ohm), the five diodes (D1, D2, D3, D4, D6) is across the input voltage, but after the fuse. The voltage from the current shunts goes to a resistor (R9: 100kOhm) and the to the main chip. The voltage input has two resistors in series (R6 & R32: 2×5Mohm) going directly to the main chip.
The battery tester for 1.5V (R36: 150ohm), 9V (R40: 910ohm) and 12V (R41: 1200ohm) do not have any overload protection, except the fuse and that is not very safe because the V input is directly connected to the resistors (mA & V input is shorted together through the fuse in these 3 ranges).
This meter has the very common small SMD resistor (R8: 910kOhm) that must handle overload on a lot of ranges: mVDC, mVAC, frequency, resistance, capacitance, diode, continuity and temperature. For resistance, capacitance, diode, continuity the PTC and the transistor pair (Q1 & Q2) protection the current output, but it is also connected in mVDC, mVAC, frequency and temperature. Frequency output is through a resistor (R17: 100kOhm), this will give a fair amount of protection, but not against high voltage.
The main chip (U2: DTM0660L) and its EEPROM (U3: K24C08) is a well proven solution is cheap meters, this meter also adds a display driver (U1: unmarked) for the inverted display. There is transistors for backlight (Q3), flashlight (Q5) and buzzer (Q4), in addition to a voltage regulator (U4: 7130). There are a few diodes (D5, D8, D10), they may be used for rotary switch encoding to the chip.
The NCV antenna is at the top.
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A closeup of the top part.
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This side only has the pads for the rotary switch, the buttons and the LCD. The LCD layout is printed on the circuit board.
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Conclusion
This is a cheap meter and as usual with cheap meters they do not live up to their CAT rating, 250VAC fuses do not match with a 1000V CAT rating. A small SMD resistor that must withstand 1000’s of volt is not realistic either. Or the battery load resistors that is directly connected to the V terminal when battery test ranges is selected.
With that said the meter do have a lot of functions and do most of it fairly well. The manual range is a bit silly, it is easy enough to select a range manually when needed with the RANGE button.
Notes
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