certificate
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CONDUCTIVITY METER utility model patent certificate
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CONDUCTIVITY METER calibration certificate
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standard block calibration certificate 1
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standard block calibration certificate 2
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standard block calibration certificate 3
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Sigma2008A series software copyright
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Sigma2008B&C series software copyright
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RESISTIVITY METER utility model patent certificate
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RESISTIVITY METER calibration certificate
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TX series software copyright
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precision resistance calibration certificate