DMM Mustool MT66

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This is a fairly cheap DMM with all the most common functions.

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I got the meter in a box with picture of the meter and supported function listed.

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

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The probes has removable tip covers. With covers on the rating is CAT III 600V, without covers CAT II 1000V.

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

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A standard cheap termocoupler.

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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 of them are used by this meter.

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

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The NCV function will show lines depending on electric field strength.



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.

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Frequency input impedance.

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mVAC input impedance, mvDC looks similar.

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The frequency range is specified to support 99MHz, but it do not.
Large DC offset voltage makes AC readings wrong.


Tear down

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Four screws and the back could be removed.

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The circuit board is shaped for the box with holes for the input terminals and cutouts for the enclosure screws in the corners.

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The circuit board was mounted with six screws.

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The uAmA current ranges uses the voltage terminal and is switches to two resistors for uA (R11 & R11B: 100ohm, 10kOhm) and one resistor for mA (R22: 0.99ohm). The resistors are protected by 5 diodes (D1..D5)
The voltage input has the very common 3 paths: Voltage input (R4A & R4B: 2x5Mohm), medium impedance (R9A, R9B, R9C: 3x300kOhm), this goes directly to the multimeter chip and low impedance (PTC) with two transistor pairs for protection for mV, ohm, temperature and frequency (Q5 & Q6 and after 1kOhm Q1 & Q2).
At the top of the circuit board is an antenna for the NCV electric field detection, it is tied to ground with a large resistor (R3: 22Mohm).
I like the PTC is at the input and that the medium impedance path is a couple of resistors in series.

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On this side of the is only the pads for the range switch, the buttons and the LCD display.

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Conclusion

The meter do not have any CAT rating on it, but the manual list CAT III 300V and CAT II 600V in different places. I might be close to fulfilling them, but the mounted fuses has to low voltage rating.

The number of ranges is fairly complete, even a NCV function is present, but the meter do not have any extra functions.

This is a fairly simple meter, but it lives up to the multimeter category in a good way with full support in all ranges for both low and high values and everything in between.




Notes

The multimeter was supplied by banggood.com for review.
The manual do not completely match the meter, there are a few differences.

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