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8 Calibration Procedure
The 1502A uses a three-point calibration scheme with a quadratic polynomial
correction function to maintain the accuracy of its resistance measurement. The
three calibration points are at 0Ω, 100Ω, and 400Ω. Three calibration pa
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rameters determine the correction function: CAL0, CAL100, and
CAL400. The CAL0 parameter sets the correction at 0Ω resistance (but
does not affect the correction at 100Ω). The CAL100 parameter sets the
correction at 100Ω resistance (but does not affect the correction at 0Ω).
The CAL400 parameter sets the correction at 400Ω resistance (but does
not affect the correction at 0 and 100Ω). Adjusting the calibration param
-
eters directly affects the measurement at the specific resistances. For
example, increasing the CAL100 parameter by 0.005 increases the
measured value at 100Ω by 0.005Ω.
8.1 Accessing the Calibration Parameters
The calibration parameters are accessed in the Cal menu. The calibration pa-
rameters are protected by requiring the correct password to access them. Press
the Menu button, “SEt?” appears. Press the Ω/Exit button and hold it down
for one second, “CAL” appears briefly. The display will show “PA= 0000”and
allow you to change the number to the correct password. You must enter the
password (“2051”). Use the L and R buttons to move between the password
digits and the U and D buttons to increase or decrease the value of a digit.
Press Enter when all the digits are correct. If the password is entered correctly
the first parameter in the calibration menu will appear.
The first parameter in the Cal menu is the lockout control parameter, indicated
on the display as “LOCOUt”. This parameter has two options, “CAL” and
“ALL”. “CAL” (default) locks out the calibration menu only. “ALL” locks out
all menus and access to any menu requires the correct password. Use the L
and R buttons to select the lockout option and press Enter to continue. The
instrument calibration parameters follow.
The calibration parameters appear with the name shown briefly then the value.
You can change the sign and digits of each parameter. Use the L and R but
-
tons to move between digits and the U and D buttons to increase or decrease
the value of the digit. Press Enter to save the new value.
The last parameter in the Cal menu is the factory reset function. This can be
used to clear the internal memory and reset all parameters to the defalut values.
This is intended to be used only at the factory.
The calibration parameters can also be set using remote commands through the
RS-232 or IEEE-488 interface. The *PA=<password><EOS> command must
be used first, using the correct password (“2051”), to enable access to the cali
-
bration parameters. Lockout protection is automatically set by cycling the
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8 Calibration Procedure
Accessing the Calibration Parameters