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Model 3550 LCR Meter Instruction Manual Operating Instructions
Making Accurate Measurements cont’d:
Zero Corrections
Residual Impedance and Leakage of test fixtures exists for all types of test fixtures. To maintain
the performance accuracy of the 3550 it is highly recommended that a zero correction be
performed whenever a change in test fixture takes place. For test fixtures such as Kelvin Klip
Leads where the positioning may vary, extra effort must be made to perform the zero correction
while positioning the leads in the exact location, as the measurement will be taken.
When performing a standard zero correction, the instrument will step through frequencies from
42Hz to 5MHz. This takes a considerable amount of time and may not be desired in certain
applications especially when the actual component test will take place at a single frequency point.
To overcome this, the 3550 has the ability to perform spot frequency corrections where zero
corrections are performed on up to three user defined frequency set points. The spot frequency
zero correction data is stored in the instrument’s non-volatile RAM and will overwrite any
correction data obtained from a standard zero correction procedure. A standard zero correction
cannot write over data from a spot frequency zero correction. The spot frequency setting must be
disabled in order for the standard zero correction to be able to write over all frequency points.
Refer to “Defining Spot-Correction Frequencies for Zero Adjustments”, [SHIFT] ĺ [8] in the front
panel description to learn how to enable or disable the spot frequency settings.
Table 4.6 - Zero Correction Limits
Zero Correction Correction Correction Limit
Open Stray Capacitance & Stray Conductance (C0)&(G0) >1kƻ
Short Residual Inductance & Residual Resistance (L0)&(R0) < 1kƻ
If during OPEN correction the Impedance is less than 1kƻ, or during SHORT correction the
Impedance is 1kƻ or higher, a buzzer will go off to warn that correction cannot be made, and
the system will reset without making the correction.
There are three methods of defining what frequencies a zero correction will be performed on. They
are Standard, Frequency Limit, and Spot Frequency Zero Correction.
Standard Zero Correction
Refer to Section 4 , “ZERO” Panel – for instructions to perform a standard open and short circuit
correction. This procedure will perform a zero correction on all test frequencies, 42Hz~5MHz
except for those designated as spot correction frequencies.
Frequency Limit Zero Correction
For zero correction, [SHIFT] ĺ [-], Correction Frequency Limit Setting Mode allows the user to
define the upper and lower frequency limits instead of using the default 42Hz~5MHz range.
Spot Frequency Zero Correction
Refer to [SHIFT] ĺ [OPEN] and [SHIFT] ĺ [SHORT] sections for instructions to perform a spot
frequency open and short zero correction procedure.
After performing the zero correction procedure, perform a “before and after” measurement on a
component with an accurately known value to confirm that a zero correction has taken place. A
calibrated capacitance or inductance standard would be ideal (but not required) for this type of
verification.
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