Is there any option or accessory available for extending the test port of the E4991A?
The E4991A-007 temperature characteristic test kit provides the test port extension cable and accessories required to perform temperature characteristics measurements. There is neither option nor accessory to support the test port extension for applications other than the temperature characteristics measurements.
When the test port needs to be extended with a coaxial cable in order to connect a DUT or a MUT, the extension cable should be made as short as possible. Perform calibration at the end of the extension cable. The extension cable, however, necessarily degrades measurement accuracy and stability. Since the cable characteristics (distributed capacitance and inductance) vary when the cable is moved, the calibration should be performed at the same position as when the DUT is connected. While measurements are performed, the extension cable must be held at the same position without being moved. Even if the calibration and measurements are performed carefully, measurable impedance range narrows due to the inherent capacitance and inductance of the extension cable. Especially, in low capacitance and low inductance measurements, test port extension should be avoided.
In order to measure a DUT away from the E4991A, it is recommended to use the E4991A-010 probe station connection kit. Install the test head closely to the DUT and interconnect the test port and the DUT with a shortest possible coaxial cable or a test fixture. The 1-meter cable assembly between the test head and the E4991A mainframe does not significantly affect measurements. This method provides much better measurement accuracy than the method of extending the test port with a long extension cable.
If the test port extension is required to measure temperature characteristics of a DUT or a MUT, it is recommended to employ the E4991A-007 temperature characteristic test kit.