Date: Fri, 19 Nov 2004 15:17:51 -0600 From: Frank J. Cuzze/AT-Austin/3M/US Subject: Characteristic Impedance for a 90211 PFC Wire Hello John, Enclosed is the data we measured on the 90211 cable assembly for characteristic impeadance. The Zo data was measured in two ways, with an LCR meter, and with a TDR. The results of both meeasurements are given below. The average Zo value with the LCR meter was 73.1 Ohms. The TDR data was measured with shield grounded and floating. From the measurements, the impedance data shows that with the shield grounded, the Zo value of the wire drops by 0.8 Ohms. The average Zo from the TDR data was 73.3 Ohms, so with the shield grounded, while the average Zo with the shield floating was 74.2 Ohms. The average value of Zo for the wire, looking at both method, appears to be very close for a grounded shield, 73.1 for the meter versus 73.3 Ohms for the TDR, and be well within the -/+ 10% tolerance range. Regards, Frank | | | Data Summary: All data supporting this test can be found HERE | | | | (Embedded image moved to file: pic12859.jpg) | | | | TDR data was also collected to see how is correlates with the resonant | | frequency, capacitance method. The TDR data is Unbalanced only and seems to | | line up very close to the data above. | | The one trace that measures high is the pin 25 which does not have a ground | | conductor on the edge. | | | | (Embedded image moved to file: pic08723.jpg) | | | | Below is another chart with the shield common with the ground wires in the | | cable. The impedance value was reduce by less than an ohm at about 0.8 ohms | | | | (Embedded image moved to file: pic09741.jpg) |