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19-6
Calibration
Current and charge calculations
When calibrating the 20pA-2µA current ranges and all charge ranges, you must calculate the
actual current or charge values from the applied calibrator voltages and the characterized Model
5156 Calibration Standard resistor and capacitor values. You can either calculate these values
manually (as in this section) or automatically as covered below.
Manual calculations
Current calculations
Calibration currents are calculated as follows:
I = V/R
Where: I = calibration current
For example, assume you are calibrating the 20pA range using a 2V calibrator voltage with
an actual 100.5GΩ standard resistor value. The actual calibration current is: 2V/100.5GΩ =
19.9004pA.
Charge calculations
Calibration charge values are calculated as follows:
Q = CV
Where: Q = calibration charge
For example, the 200nC range calibration charge value using 2V with a 99.5nF standard
capacitance value is: 2V × 99.5nF = 199nC.
Automatic calculations
As an alternative to manual calculations, you can use a computer to read the standard values
from Model 5156 via remote programming commands, and then have the computer perform the
calculations. See Appendix H for details. Note that you can use the *OPT? command (Section
14) to determine if the Model 5156 is properly connected.
V = calibrator voltage
R = actual standard resistor value
C = actual standard capacitance value
V = calibrator voltage
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