9 Calibration
The 1521 shouldb ecalibrated at regular intervals to ensure that it continues to
measure with proper accuracy.Calibration should only be done by qualified,
authorized personnel.

9.1 Required Equipment

The followingitems are required to test and calibrate the 1521:
•0Ωfour-wire resistor (short)
•25Ωfour-wire resistor, uncertainty within 20ppm (±0.0005 Ω)
•100Ωfour-wire resistor, uncertainty within 20ppm (±0.002 Ω)
•400Ωfour-wire resistor, uncertainty within 20ppm (±0.008 Ω)
•4 kΩfour-wire resistor, uncertainty within 50ppm (±0.2 Ω)
•10 kΩfour-wire resistor, uncertainty within 50ppm (±0.5 Ω)
•40 kΩfour-wire resistor, uncertainty within 50ppm (±2 Ω)
•100 kΩfour-wire resistor, uncertainty within 50ppm (±5 Ω)
•500 kΩfour-wire resistor, uncertainty within 75ppm (±37.5 Ω)
Each resistormust be attached with an INFO-CON probe connector. The 25Ω,
100Ω, and 400Ωresistorsmust be programmed with the CVD probe type with
unitsset to ohms. The 4 kΩ,10kΩ,40kΩ,100 kΩ, and 500 kΩresistors must
be programmed with theTHERM probe type with units set to ohms.

9.2 Calibration Procedure

Calibration requires adjustment of the CAL1 and CAL2 parameters at 100Ω
and10kΩrespectively(see Section 7.8.20). The calibration parameters can be
accessed from thefront panel by pressing the MODE button and holding it for
three seconds, releasingit, then pressing the ENT button (see Section 7.8 ). You
must enterthe pass-code to continue (see Section 7.8.4). The step-by-step pro-
cedureisasfollows:
1. Connect the 100Ωresistor.Adjust the CAL1 parameter by subtracting the
measured error.For example, if the resistor is exactly 100.000Ωand the 1521
measures 100.029Ω, CAL1 shouldbe adjusted by subtracting 0.029 from the
current valueof CAL1.
2. Verifythe accuracy at 0Ω, 25Ω, 100Ω, and 400Ω.
3. Connect the 10 kΩresistor.Adjust the CAL2 parameter by subtracting the
measured error.For example, if the resistor is exactly 10.0000 kΩand the 1521
measures 10.0029 kΩ, CAL2 shouldbe adjusted by subtracting 2.9 from the
current valueof CAL2.
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9 Calibration
Required Equipment