DMM DT-830B

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This is a really cheap DMM with manual ranges and a minimum of functions.

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There was no box included with the DMM.

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It included the DMM, a pair of probes and a instruction sheet.
The instruction sheet includes specifications for temperature measurement, battery test and also has text about fuse replacement, i.e. it do not match the meter, even though it has a fairly correct drawing of the meter..

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The standard probes are rather tiny, but marked that they can handle 1000V.

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They use 4mm plugs, but they are not shrouded and very short.

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On the back it says to use a 0.5A fuse, but there is no fuse inside.

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To replace the battery the meter must be opened



Display

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Typical display during usage, it will show the number.

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The HV letters is only shown in the 750/1000V ranges.



Functions

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The range switch is not very precise and do not always connect correctly.
Rotary switch:


Input

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Measurements

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I do not believe the specified tolerances, the included manual did not match the DMM.
On 2000uA range the meter is unstable (probably the switch) and may show 30% too much sometimes.
On 10A range the shunt will heat up and the meter go show more 11A with 10A current.
The low ohm range shows too low a value (100ohms can shows 90ohm).


Tear down

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Two screws and the back could be removed, this is required to replace the battery.

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The circuit board is minimal in size.

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Three screws more and I could remove the circuit board.

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I left the LCD display and zebra stripe in.

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There is not many parts on the circuit board. At the input terminals is some of the resistors for the current ranges: 10A (R24: 0.010ohm R25: 0.100ohm), 200mA (R13: 1.00ohm), 20mA (R15: 9.00ohm + R13), 2000uA (R7: 100ohm), 200uA (R8: 900ohm + R7).
The resistors (R12, R10, R10, R8, R19, R7) is also used for voltage input and the diode (D1) is used for rectification in the AC voltage ranges.
There is no trimpot this probably means that the IC contains a EEPROM and some calibration values are stored in it during final test.

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On this side of the circuit board is the range switch and the transistor tester socket. It also looks like some "dirt" on the circuit board

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Conclusion

This is a well known and very cheap meter, usual it is fairly precise, but occasionally there is intermittent contact in the range switch and it shows a wrong value.
It is very limited in ranges and functions and with a wrongly working diode range.
There is nothing that looks like input protection or fuses, i.e. keep it away from mains and high current.
I do not like this meter it is not reliable enough.



Notes

This meter exist in more than one version with the same type number.

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