EN 60444-11-2010 pdf download.Measurement of quartz crystal unit parameters -Part 11: Standard method for the determination of the load resonance frequencyfL and the effective load capacitance Cleft using automatic network analyzer techniques and error correction (IEC 60444-11:2010).
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
IEC 60122-1:2002, Quartz crystal units of assessed quality — Part 1: Generic specification
IEC/TR 60444-4, Measurement of quartz crystal unit parameters by zero phase technique in a it-network — Part 4: Method for the measurement of the load resonance frequency 1L’ load resonance resistance RL and the calculation of other derived values of quartz crystal units, up to 30 MHz
IEC 60444-5:1995, Measurement of quartz crystal units parameters — Part 5: Methods for the determination of equivalent electrical parameters using automatic network analyzer techniques and error correction
3 General concepts
3.1 Load resonance frequenciesf and fLa
As can be seen in Figure 1, there are two intersection frequencies where V = XCL’‘LI- with high admittance (low impedance) and ‘La with low admittance (high Impedance).
The load resonant frequency fL is one of the two frequencies of a crystal unit in association with a series or with a parallel load capacitance, at which the electrical admittance (respectively impedance) of the combination is resistive, The load resonance frequency ‘L is the lower of the two frequencies.
In a first approximation IL can be calculated by:
4 Reference plane and test conditions
4.1 General
Reference plane: as in 8.4 of IEC 60444-5:1995.
Test conditions: crystal case not grounded.
Level of drive: the output level of the generator Es set, such that at its (series) resonance frequency, the crystal under test is measured at the nominal drive level.
The measurement at the load resonance frequency using the method described below leads to a level of drive, which is remarkably lower than at the (series) resonance frequency due to the relative high reactance value. Therefore a correction measurement is performed, for details see 4.2.
4.2 Principle of measurement
The principles of measurement are the following.
a) Calibration
Due to the high impedance measurements with this method special care has to be taken in
the calibration of the test set-up.
Similar to IEC 60444-5:1995, use the following three known calibration elements:
1) short-circuit (0 11) or resistor with low resistance;
2) resistor of 25 fl or 50 nominal;
3) open circuit (infinite resistance) or capacitor of 10 pF nominal;
where Z1 is the impedance of calibration element I Z2 is the impedance of calibration element 2
Z3 is the impedance of calibration element 3
is the measured voltage with calibration element 1
V2 is the measured voltage with calibration element 2
V3 is the measured voltage with calibration element 3
The following parameters are then used for the measurement of quartz crystal units:
RT is the termination impedance of the ,t-network
V is the error-corrected shorr voltage
L is the error-corrected open voltage
d) Comparison with the method of IEC 60444-4
The inaccuracy of the measurement of the load resonance frequency f1according to IEC 60444=4 Is mainly given by the inaccuracy of the physical load capacitors which often show a large dependence on frequency.
Comparison measurements ((1)1, (2]. (5)) with quartz crystal units between 4 MHz and
155 MHz showed an inaccuracy of I % of CLOII.
The corresponding frequency inaccuracy can be calculated with the formula (20). The inaccuracy for fundamental quartz crystal units with high C1 is less than 5 ppm with the standard method presented here and up to 20 ppm with the method of IEC 60444-4.
Several series of comparative measurements ([1], [2)) have proven that the reproducibility between different test systems using the standard method is considerably better than with the IEC 60444-4 method.
e) Limitations
This method shall not be used for measurements of aging and for the measurement of load resonance in the temperature range due to the still remaining measurement uncertainty.
In the presence of activity dips, the described method may yield unacceptable results and therefore care should be taken.
If narrow frequency tolerances of ‘L are required in an application, it is recommended to determine the effective CL of the application circuit by a correlation measurement. Generally the error Of IL becomes large when CL is smaller than 10 pF or 2 x.EN 60444-11-2010 pdf download.
EN 60444-11-2010 pdf download
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