Test/review of DMM WinApex ET8102

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HKJ
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Test/review of DMM WinApex ET8102

DMM WinApex ET8102
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This is a fairly cheap true rms multimeter.
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I got it in a typical cheap multimeter box, the drawing mostly match the meter.
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That was the meter, the probes, a thermocoupler and a manual.
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Probes are marked CAT III, but do not have the (partial) tip covers, this means they are CAT II.
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The plugs are fully shrouded, but the shroud is a bit short
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The thermocoupler is the standard cheap type with banana plugs, the cable is rather thin.
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The meter is not very heavy making it difficult to turn the range switch or press buttons without the meter moving around when on tilted.
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Display
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All the segments are shown during power on, but not all are used.
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Typical display during usage, it will show the number and selected measurement
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The NCV indicator, in addition to the bars the beeper will sound.
Functions
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Buttons:


  • Select (Yellow): Select DC/AC in current modes, continuity, diode, capacity, temperature in ohm mode and can also be used to show duty cycle in Hz mode and frequency and duty cycle in AC mode.
  • Hold: Will freeze the display reading, until pressed again, hold down to activate the background light.
  • Range, REL: Select manual range and change range, hold down to reactivate automatic ranging. In capacitance it is a REL function to zero out and offset.
  • Max/min: Capture maximum and minimum values, it will change between max/min/actual, holding it down will activate flashlight.

Rotary switch:

  • Off: Meter is turned off
  • VAC: AC voltage and frequency/duty-cycle, the frequency input has high sensitivity and low bandwidth.
  • VDC: DC voltage
  • ohm: Ohm, diode, continuity, capacitance, temperature Fahrenheit, temperature Celsius
  • Hz: Logical frequency input, can also show duty cycle.
  • A: Ampere DC or AC
  • mA: Milli ampere DC or AC
  • uA: Micro ampere DC or AC
  • Test: Phase detection with one connection. This will show 0 or OL in the display, OL means phase detected.
  • NCV: Non-contact voltage or electric field detection.

Input
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  • 10ADC: 10A DC current input.
  • COM: The common terminal for all ranges.
  • xxx: All other ranges, including uA and mA.

Measurements

  • Volt and frequency

    • 1V AC readings is 5% down at 2.3kHz, rms will not work at that frequency
    • AC frequency range with 0.1V input is from 1.1Hz to 2.5kHz
    • AC frequency range with 0.1V input it can be stretched to 32kHz
    • AC frequency range requires a zero crossing.
    • Frequency input can handle +/-2.8V offset with 1Vrms input.
    • At 1Vrms frequency input range is from 1.1Hz to 44MHz
    • Duty cycle works from 1% to 99% at 100kHz with 4Vpp, precision is within 0.3.
    • Max/min needs about 200ms to capture a voltage, autorange is disabled when using this function and it will not capture every max/min.
    • Input impedance is 10-11Mohm on DC and AC
    • Frequency input is 2-3kOhm in input impedance above 2V
    • Input protection is 1000VDC/750VAC
    • Frequency input is protected to 250V or 550V DC or AC peak (Both values are specified).

  • Current

    • 10A range has audible alarm above 10A
    • 10A range is fused with a 10A/250V 5×20mm fuse
    • mAuA range is fused with a 0.6A/250V 5×20mm fuse
    • Current ranges starts in DC
    • Input voltage must not be more than 36VDC or 25VAC

  • Ohm, continuity, diode and capacitance

    • Ohm needs about 2.5s to measure 100ohm
    • Ohm voltage is 1.1V open and 0.25mA shorted.
    • Continuity is fast (About 20ms).
    • Continuity beeps when resistance is below 50ohm.
    • Continuity is 2.1V open and 0.25mA shorted
    • Diode range uses 4.0V, max. display is 3.3V at 0.25mA, max. current is 1.5mA shorted
    • 10uF takes about 2.5 seconds to measure.
    • 70000uF takes about 7 seconds to measure.
    • Overload protection is 550V DC or AC peak

  • Miscellaneous

    • Current consumption of meter is 1.6mA, 8.2mA with backlight, 9.1mA with backlight and 13.3mA with both.
    • Meter turns off at 2.2V, battery symbol show at 2.3V.
    • Readings will be correct until meter turns off.
    • Backlight fades with dropping voltage, but it usable until meter turns off.
    • Flashlight fades with dropping voltage, but it usable until meter turns off.
    • Viewing angle is good except from the top.
    • Display updates around 3 times/sec
    • Backlight will automatic turn off after about 12 seconds.
    • Flashlight will not automatic turn off, but turns off when the meter turns off.
    • Will automatic turn power off in about 17 minutes.
    • Standard probes cannot be fully seated in the meter, but they do connect (About 5mm stick up).
    • The meter usual need a few display update to before it display the value.
    • Weight is 209g without accessories, but with sleeve and battery.
    • Size is 145 × 70 × 37mm with sleeve

  • Probes

    • Probe resistance 46mOhm for one.
    • Probe wire is soft and 73cm long.


1uF
A look at the capacitance measuring waveform with a 1uF capacitor.
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The logical frequency input is about 2-3kOhm in input impedance.
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High DC voltage will block for AC readings.
Tear down
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I had to remove the sleeve and four screws to open the meter.
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The circuit board is not shaped like the enclosure, but is just a rectangle. The NCV bulb is empty, the antenna is only the circuit board.
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There was 6 screws holding the circuit board in.
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There is only a limited amount of parts on this side: The two fuses, a PTC for protection, the buzzer, crystal, capacitor and the flashlight led.
The two points marked SW1 & CAL is accessible from the battery compartment without opening the meter.
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The meter is on this side. The current input has a wire shunt for the 10A range and next to it the 1ohm and 99ohm for the mA and uA ranges, they are protected with a TVS diode (D3). The voltage input has the usual 10Mohm input made from two 5Mohm resistors.
The ohm range uses the PTC and a transistor pair (Q1 & Q2) for protection, but do also have a sense path through a small SMD resistor (R7: 1Mohm).
The NCV antenna is at the top of the circuit board and has a high ohmic resistor (R40: 22Mohm).
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Conclusion
As usual I do not believe the CAT rating, 250V fuses and a small SMD resistor on ohm input is not enough.
The meter looks very cost optimized, but it has a lot of functions, only mV is missing. The ohm position is rather busy with 6 selections.
Notes
This meter exist with many different names on it and small variations in functions.
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