3-12. COMPENSATION
The 4278A has four compensation functions -- Open, Short, Standard, and Temperature.
3-12-1. OPEN COMPENSATION
The open compensation capability compensates for the stray admittance existing from the
calibration plane (depends on the CABLE LENGTH selection) to the connection contacts for
the capacitor. First, without connecting a capacitor, press the 'OPEN COMPEN' softkey to
measure the open admittance (capacitance and conductance), then press the 'OPEN ON'
softkey to enable compensation calculations on subsequent measurements. The open
admittance data is dependent on the frequency setting for the test signal. This data is stored
in nonvolatile memory.
3-12-2. SHORT COMPENSATION
The short compensation function compensates for the residual impedance existing from the
calibration plane (depends on the CABLE LENGTH selection) to the connection contacts for
the capacitor. First, short the capacitor contacts together, then press the 'SHORT COMPEN'
softkey to make a short impedance (inductance and resistance) measurement, then press
the 'SHORT ON' softkey to enable the compensation calculation. The short impedance data
is dependent on the frequency setting for the test signal. This data is stored in nonvolatile
memory.
3-12-3. STANDARD COMPENSATION
The standard compensation function is used to compensate for other errors by using the
transmission coefficient derived from the relationship between the working standard's (pre-
measured) reference value and the actual (uncompensated) measurement value. First enter
the working standard's (pre-measured) reference value. The reference value should be
premeasured value of the Cp-D or Cp-G parameter. To make this selection press the 'STD
PARMTR' softkey and either the `C-D' softkey (for Cp-D parameter) or the `C-G' softkey (for
the Cp-G parameter). Then connect the working standard as the DUT and press the 'STD
COMPEN' softkey. Then press the 'STD ON' softkey to execute the compensation calcula-
tion. The working standard's reference data and its measurement data are dependent on
frequency setting of the test signal. These data are stored in nonvolatile memory.
3-12-4. TEMPERATURE COMPENSATION
The temperature compensation function is used to minimize the temperature induced mea-
surement error of the analog measurement circuit. When you press the 'TEMP COMPEN'
softkey, the 4278A measures the key offset voltages in the measurement circuit and com-
pensates the measurement value on subsequent measurements. The compensation data is
stored in volatile memory, so once you turn the 4278A off, the temperature compensation
data will be reset. Press the 'TEMP COMPEN' softkey when you are making accurate
measurements.
3-22
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