TM 10-6630-246-12&P TM 09241 B-12&P Table 2-4. Calibration and Measurement Error Codes Error Code Description Action/Remedy E-20 Out of range If  this  occurs  only  when  electrode  is  out  of solution being   checked,   the   code   should   disappear when returned to the solution Check   electrode   and   probe   connections   to meter. Recalibrate using fresh standard buffer solutions. E-21 Automatic calibration error Press any key to reset. Check that proper standard buffer solution is being used. Clean electrode bulb by vigorously stirring in demineralized or distilled water or by squirting water from wash bottle. Recalibrate using fresh standard buffer solution. If error code repeats, replace electrode. E-22 Calibration   standard   error.   Two   of the  same  standard  buffer  solutions are being measured. Press any key to reset. Check    that    two    different    standard    buffer solutions are being   used   and   the   correct   one   is   being measured. Recalibrate using fresh standard buffer solutions. E-23 Electrode slope is not within 80% to 120%  range. Press any key to reset. Clean electrode bulb by vigorously stirring in demineralized or distilled water or by squirting water from wash bottle. Recalibrate using fresh standard buffer solution. If error code repeats, replace electrode. E-31 A  value  has  been  entered  which  is not within the acceptable range. Press any key to reset. Enter a new value. Acceptable values are: pH: -2.00 to +19.999. pH Slope: 80% to 120%. Timer   Interval:   5   seconds   to   23   hours   59 minutes. 2-31