5520A
Operators Manual
4-6
4-8. Using the Format EEPROM Menu
Caution
Use with extreme care. The format nonvolatile memory menu
softkeys permanently erase calibration constants. Pressing
ALL or CAL invalidates the state of calibration of the 5520A.
Pressing FORMAT NV MEM in the utility functions menu opens the following:
nn067f.eps
All the softkeys in this menu require the rear panel CALIBRATION switch to be in the
ENABLE position. The nonvolatile memory contains calibration constants and dates,
setup parameters, and the user report string. In the case of calibration constants, factory
defaults are the same for all Calibrators. They are not the calibration constants obtained
when the 5520A was calibrated by the factory before shipment. The softkeys are:
• ALL replaces the entire contents of the EEPROM with factory defaults. This would
be used by service personnel after replacing the EEPROM, for example. It is not
required in normal use.
• CAL replaces all calibration constants with factory defaults but leaves all the setup
parameters unchanged. This is also not required in normal use.
• SETUP replaces the setup parameters with factory defaults (Table 3-3) but leaves
the state of calibration unchanged. You do not have to break the calibration sticker
for this operation. Remote commands can also change the setup parameters. (See
these commands in Chapter 6: SRQSTR, SPLSTR, *PUD, SP_SET, UUT_SET,
TEMP_STD, DATEFMT, PRES_UNIT_D, RTD_TYPE_D, TC_TYPE_D, LIMIT.)
4-9. Resetting the Calibrator
At any time during front panel operation (not remote operation), you can return the
5520A Calibrator to the power-up state by pressing R, except after an error message,
which is cleared by pressing a blue softkey. Pressing the R key does the following:
• Returns the calibrator to the power-up state: 0 V dc, standby, 330 mV range and all
OUTPUT SETUP menus set to their most recent default values.
• Clears the stored values for limits and error mode reference.
4-10. Zeroing the Calibrator
Zeroing recalibrates internal circuitry, most notably dc offsets in all ranges of operation.
To meet the specifications in Chapter 1, zeroing is required every seven days, or when
the 5520A Calibrator ambient temperature changes by more than 5°C. The tightest ohms
specifications are maintained with a zero cal every 12 hours within ±1°C of use. The
Calibrator displays a message when it is time to zero the calibrator. Zeroing is
particularly important when your calibration workload has 1 mΩ and 1 mV resolution,
and when there has been a significant temperature change in the 5520A Calibrator work
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