YOKOGAWA Vigilantplant ST401G User Manual (English)

Questions and Answers:

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Christopher HooperAug 20, 2025
How to resolve Err. 7 (Response Error during Zero and / or Span Calibration) on YOKOGAWA Vigilantplant ST401G Measuring Instruments?
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  Zachary OliverAug 20, 2025
  To resolve Err. 7, confirm response recovery after polishing the indicator electrode with alumina. Also, check that the stability determination parameters “*?T. SEC”, “ *?PPM ”, and “*CT.min” set in service code 04 are correct. If the parameters are correct but there is still no response recovery, the indicator electrode may have deteriorated and should be replaced.
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jgonzalezAug 22, 2025
How to fix large measurement error on YOKOGAWA Vigilantplant ST401G?
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  kmeyerAug 22, 2025
  To address large measurement errors, try the following: * Polish the indicator electrode. * Clean the ceramic beads (or replace them if cleaning is insufficient). * Conduct zero and/or span calibration. * Replace the activated charcoal filter if auto zero calibration is abnormal or the piping related to auto zero calibration is blocked.
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johnsonamandaAug 25, 2025
What to do if the measured value is abnormal in YOKOGAWA Measuring Instruments?
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  cariasAug 25, 2025
  If the measured value is abnormal, it might be due to several reasons: * The indicator electrode may have stopped because the electrode drive belt doesn't turn. If the electrode drive belt does not turn, sufficiently tighten the set screw. The cell motor may not run. If the cell motor does not run, replace the motor with a new one. * The indicator electrode may have worn out; replace it with a new one. * There may be insufficient continuity at the electrode mechanism block; replace the rotating contact.
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Tracy SawyerAug 26, 2025
Why does the measured value fluctuate largely on YOKOGAWA Vigilantplant ST401G Measuring Instruments?
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  Jacob WebbAug 26, 2025
  Large fluctuations in measured values can occur if: * The indicator electrode does not rotate at a constant speed. Check if the set screws have loosened and if the belt and driven shaft assembly are normal. If not, replace them. * There is insufficient continuity at the electrode mechanism block. Replace the rotating contact.
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Gabriel MooreAug 27, 2025
What to do if the measured value does not vary on YOKOGAWA Vigilantplant ST401G Measuring Instruments?
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  Daryl MartinAug 28, 2025
  If the measured value does not vary, consider these possibilities: * The measuring tank may have no sample water. Repair any abnormalities such as piping disconnection or sample water feed failure to restore normal conditions. * The electrode to electrode circuit may be open. Repair the open circuit, or replace the electrode if the open circuit occurs in it. * No voltage may be applied between the indicator and counter electrodes. Check the converter.
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walterchristianAug 29, 2025
What causes Err. 5 (Slope Error) on YOKOGAWA Vigilantplant ST401G and how to fix it?
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  Jennifer KingAug 29, 2025
  Err. 5 (Slope Error) can be caused by aged calibration standard solution, incorrect concentration value, or a deteriorated indicator electrode. Confirm if any of these are present. If the error persists after recalibration with a new solution or polishing the electrode with alumina, the indicator electrode should be replaced.
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Jennifer MoralesAug 31, 2025
Why does the reading deviate significantly or overshoot on YOKOGAWA Vigilantplant ST401G?
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  peterhowellAug 31, 2025
  Significant deviation or overshoot in readings can occur if span calibration was not performed correctly, particularly if electrode sensitivity initialization was set to ON (1) in service code 08 (“CHANG” Mode) and a calibration solution with a large concentration difference was used. Set electrode sensitivity initialization to ON (1) in service code 08 (“CHANG” Mode) and perform calibration again.
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Christopher RichardsonSep 2, 2025
How to fix Err. 2 (Sample Temperature Error) on YOKOGAWA Vigilantplant ST401G Measuring Instruments?
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  castrochristopherSep 2, 2025
  To fix Err. 2 (Sample Temperature Error), control the sample temperature to be in the range of 0.0 to 50.0°C. If the error persists within this range, the RTD may be defective (open circuited), and the counter electrode should be replaced.
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Patrick FlemingSep 4, 2025
What causes Err. 6 (Zero Point Error) on YOKOGAWA Vigilantplant ST401G?
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  Ann SimmonsSep 4, 2025
  Err. 6 (Zero Point Error) may be caused by chlorine entering the chlorine-free water used for calibration (when the chlorine-free-water-based measuring method applies), or the indicator electrode or counter electrode may be defective. Confirm if any of these is the cause.
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Mark CaseySep 5, 2025
What to do for Err. 8 (Temperature Compensation Range Exceeded) on YOKOGAWA Vigilantplant ST401G Measuring Instruments?
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  Rebecca HamptonSep 5, 2025
  To address Err. 8 (Temperature Compensation Range Exceeded), control the sample temperature to be in the range of 0.0 to 40.0°C.