61E 它表 ACV 問題

隻Uni-T 61E尋日攞嚟度power cord出~310V, 今日度都有~280V.
電阻同DCV唔覺有事,初頭以為true RMS有事,
後尾發覺人手去唔同range有0.9V / 9V / 90V不等offset(它筆無掂野)
應該係邊都有事?會唔會跌機震到lost calibration?

Search到呢度有人寫
https://www.eevblog.com/forum/testgear/unit-61e-accuracy/

It appears that VR3 is for adjusting resistance readings, and VR1 is for the DC adjust, VR2 for AC volts and VR4 is to adjust the TRMS chip DC offset. Sorry this might be wrong but it was just a quick skim through the data.

咁我呢個case係咪應該調VR4?

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這款錶點操作/調校唔多清楚
但無參考電壓源或高於4倍以上的儀錶作比較, 係唔應該隨便調啲VR的

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本帖最後由 Joe_Black 於 2020-6-14 22:59 編輯

Sorry,... 原來2樓link已經有電路圖

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Search到呢度有人寫
咁我呢個case係咪應該調VR4?
kwliu 發表於 2020-6-14 22:32


RMS.jpg
2020-6-14 22:47

先check下擰制的接點有無問題,之後再Check下RMS電路的電容睇下有無事。

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先多謝各位師兄熱心,屋企得一個它表,不過好在有數碼管電壓表頭,度個電池得5.xV, 聽日先買新電再試,奇怪在點解無low batt warning.

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先多謝各位師兄熱心,屋企得一個它表,不過好在有數碼管電壓表頭,度個電池得5.xV, 聽日先買新電再試,奇怪 ...
kwliu 發表於 2020-6-14 23:12


睇 ES51922 datasheet,pin 128 低過 1.2V 先提你無電
R25 R26 將電池除到 0.326。可能9V 電池跌到 3.6V 先提你

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先多謝各位師兄熱心,屋企得一個它表,不過好在有數碼管電壓表頭,度個電池得5.xV, 聽日先買新電再試,奇怪 ...
kwliu 發表於 2020-6-14 23:12



    UNI-T的錶, 我都有隻平野33C, 沒電時度出來會有好大誤差..

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無電?

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哎,換咗新電都唔得,而家個offset仲大咗。
諗緊扭VR人肉cal / check零件定係放棄ACV

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