DMM 5 in 1 (VA19)

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This is a fairly cheap DMM with all common function and some environment measurements also.
The one I got do not have a brand name on it.

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It included the DMM, a pair of probes, a pair of probes with aligator clips, a thermocoupler and a manual.

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The ony rating on the probe is 10A. The isolated tip is nice.

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The termocoupler looks fairly standard

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When using the tilting bale the meter is not stable enough to turn the switch and push the buttons.

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On the top of the meter is the microphone, photo sensor and humidity sensor. Due to the construction of the meter it is not possible to alight the light sensor directly vertical or horizontal except on eyesight.

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Space is very tight in the battery compartment, this is not very nice.





Display

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The above picture shows all voltmeter the segments on the display, segments for enviroment is not shown.

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Here is one of the symbols missing above (x10 Lux).

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



Functions

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Buttons: Rotary switch:
Input

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The terminals are a bit loose in the mounting due to the way they are made. Standard probes will fit.



Measurements
Spaceing between input terminals is not standard! 1uF

A look at the capacity measurement waveform.

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Frequency input impedance.

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Temperature input impedance.

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The capacity in about 4% wrong in 1nF range.
AC voltage is about 10% low.
Lux range is 4000 and 40000lux


Tear down

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Four screws and the back could be removed.

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6 more screws for the front.

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And four more screws to remove the circuit board.

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Not much on this side, the green resistor is the 400mA shunt. The wire below the two red terminals is the missing 10A fuse.

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There is lot of chips on this side and also a lot of trimmers (I counted 12), I tried to identify some of the chips:
IC3: 27L2C - TLC27L2 Dual precision OpAmp
IC7, IC8, IC9, IC10, IC11: GZ525 (ST) - probably a dual OpAmp
IC5: 271C - (TI) TLC271C Programable OpAmp
IC6: LM358 (TI) - Dual OpAmp
IC2, IC12: 7530-1 - Voltage regulator
Generally there is not much protection, near the voltage input is a green PTC

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At the front/top is the sensors. A humidity sensor (White ceramic), a photo diode on its own circuit board and a microphone.

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Conclusion

Without a fuse on the 10A range the meter can not live up to any CAT rating.
I have not done a fast check of the environment functions and they did not look very precise. The normal DMM functions works fine, but it is missing uA and have a fairly high burden voltage in the 400mA range.
For comparing light sources with the same type of bulb the light meter is fine, but it cannot compare a led to a incandescent correctly, with sound it can compare noise from the same source, but because its sensitivity do no match the ear, it cannot be used to evaluate noise levels.



Notes

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