BS EN 60512-25-3-2001 pdf download.Connectors for electronic equipment Tests and measurement
Part 25-3: Test 25c Rise time degradation.
This part of IEC 60512 applies to electrical connectors, sockets, cable assemblies or interconnection systems.
This standard describes a method for measuring the effect a specimen has on the rise time of a signal passing through it.
1.2 DefInitions
For the purpose of this part of IEC 60512, the following definitions apply.
1.2.1
rise time degradation
increase in rise time to a theoretically perfect (zero rise time) voltage step when the specimen is inserted in the transmission path; see figure 1. The formula used to calculate rise time degradation for gaussian signals from 10 % to 90 % is as follows:
Rise time degradation = square root [(measured rise time)2 — (measurement system rise time )2j
1.2.2
measurement system rise time
rise time measured with fixture in place, without the specimen, and with filtenng (or normalization). Rise time is typically measured from 10 % to 90 % levels; see figure 1
1.2.3
specimen environment impedance
impedance presented to the signal conductors by the fixture. This impedance is a result of transmission lines, termination resistors, attached receivers and signal sources, and fixture parasitics
1.2.4
rise time
time required for a voltage step to occur, measured between its initial value and final value, typically from 10 % to 90 % levels
2 Test resources
2.1 Equipment
Pulse generator and oscilloscope, time domain reflectometer (TDR) or other suitable equipment with a measurement system rise time less than or equal to 70 % of the measured rise time.
Unless otherwise specified in the referencing document, the specimen environment impedance shall match the impedance of the test equipment. Typically, this will be 50 ≤2 for single-ended measurements and 100 fl for differential.
2.2.1 Method A, single-ended
The fixture shall allow one signal line to be driven at a time. The driven line shall be terminated according to one of the methods of figure A2 with the specimen environment impedance. Unless otherwise specified, a 1:1 signal-to-ground ratio shall be used with each end having all grounds commoned. Each line adjacent to the driven line shall also be terminated in its specimen environment impedance at both near and far ends.
2.2.1.1 Insertion technique
The fixture shall be designed to allow measurement of rise time with and without the
specimen; see figure Ala.
2.2.1.2 Reference fixture technique
Two fixtures shall be designed to have the same fixture electrical length and characteristics of environment transmission line. The specimen fixture includes the specimen. The reference fixtures does not include the specimen. The fixture electrical length does not include the specimen length; see figure A.lb.
2.2.2 Method B, differentially driven
The fixture shall allow one signal pair to be driven at a time. The driven line shall be terminated according to one of the methods of figure A.3 with the specimen environment impedance. Unless otherwise specified, a 2:1 signal-to-ground ratio shall be used. Each line adjacent to the driven line shall also be terminated in the specimen environment Impedance at both near and far ends.
2.2.2.1 Insertion technique
The fixture shall be designed to allow measurement of rise time with and without the specimen; see figure Ala.
2.2.2.2 Reference fixture technique
Two fixtures shall be designed to have the same fixture electrical length and characteristics of environment transmission line. The specimen fixture” includes the specimen. The reference fixture” does not include the specimen. The fixture electrical length does not include the specimen length; see figure A.lb.
4 Test procedure
Unless otherwise specified, the measurement system rise time shall be less than or equal to 70 % of the measured rise time with the specimen, see figure 1. It is recommended to use the fastest output signal of which the equipment Is capable. Each of the two techniques below apply to both single-ended and differential measurements. For differential measurements, it is necessary to determine if any phase and/or amplitude errors exist between the channels, and to provide necessary compensation for these errors. Place the specimen a minimum of 5 cm from any object that would affect measured results.
NOTE The test professional should be aware of limitations or any mathematical operation(s) performed by an Instrument (e.g. normalization or software filtering).
4.1 Insertion technique
4.1.1 Measure the rise time and plot the waveform of the output signal that is transmitted through the fixture without the specimen and with filtering or normalization. This is the measurement system rise time.
4.1.2 Measure the rise time and plot the waveform of the output signal that is transmitted through the fixture wffl the specimen and with filtering or normalization. This is the measured rise time.
4.2 Reference fixture technique
4.2.1 Measure the rise time and plot the waveform of the output signal that is transmitted through the reference fixture without the specimen and with filtering or normalization. This is the measurement system rise time.
4.2.2 Measure the rise time and plot the waveform of the output signal that is transmitted through the reference fixture jjjj the specimen and with filtering or normalization. This is the measured rise time.
4.3 Rise time degradation calculation
If the signal is Gaussian in nature and the rise time was measured from 10 % to 90 % levels, then calculate the rise time degradation as follows:
Rise time degradation = square root [(measured rise time)2 — (measurement system rise time)2)
The equation may not be used if the signal was not Gaussian in nature or the signal rise time was not measured from 10 % to 90 % levels. In this case, report the measured rise times and waveform plots.BS EN 60512-25-3-2001 pdf download.