6 Performance Tests and Calibration200 Keysight U1253B User’s and Service GuideCalibration countThe calibration count feature provides an independent “serialization” of yourcalibrations. With it, you can determine the number of times your instrument hasbeen calibrated. By monitoring the calibration count, you can tell whether anunauthorized calibration has been performed. The value will increment by oneeach time the instrument is calibrated.The calibration count is stored in a nonvolatile EEPROM memory, the contents ofwhich do not change even after the instrument is switched off or after a remoteinterface reset. Your U1253B true RMS OLED multimeter had been calibratedbefore leaving the factory. When you receive your multimeter, make sure to readthe calibration count and record it for maintenance purpose.The calibration count increases up to a maximum of 65535, after which it wrapsaround to 0. There is no way to program or reset the calibration count. It is anindependent electronic “serialization” value.To view the present calibration count, unsecure the instrument from the frontpanel (see “Unsecuring the instrument for calibration” on page 180), and thenpress to view the calibration count. Press again to exit the calibrationcount display.Notes for list of calibration items:[a] Press or to select the calibration item (if not performing the complete set of calibration). After successfully calibrating an item, themultimeter will automatically proceed to the next item.[b] Both AC V positions must be calibrated individually.[c] The minimum AC current output of the Fluke 5520A calibrator is 29.0 μA, therefore, an output of at least 30.0 μA must be set for thecalibrator.[d] Be sure to recalibrate the “Short” using the dual banana plug with copper wire after performing calibration for resistance.[e] Ensure that the multimeter is turned on and stabilized for at least 60 minutes, with the K-type thermocouple connected between themultimeter and the calibrator out terminal.— Set the 5520A to internal reference.— Prior to performing adjustment, connect one end of the K-type thermocouple (with miniature TC connector on both ends) to the 5520A TCoutput, and the other end to a precision thermometer to verify that the source outputs the desired value. Adjust the source accordingly ifnecessary.— To perform the adjustment, connect one end of the K-type thermocouple (with miniature TC connector on both ends) to the 5520A TCoutput, and the other end to the multimeter via a TC-to-banana adapter. Allow at least 1 hour for the multimeter to stabilize.Table 6-4 List of calibration items (continued)Function Range Calibration item [a] Reference input
