Frequently Asked Questions

Q: I can’t communicate with the VNA. What should I do?

A: Open the National Instrument (NI) "Measurement and Automation Explorer" or the Agilent "Connection Expert" and look for the list of connected instruments. If you don't see your VNA there, then the VISA driver may be missing. The DAK software needs VISA drivers to be able to communicate with the VNA. The NI Measurement and Automation Explorer doesn’t contain VISA drivers by default. Reinstall the NI-488.2 for Windows and be sure that the necessary check-box for the drivers is selected (NI-VISA Run Time Support). The Agilent IO Libraries Suite installs the VISA drivers by default.

Q: I see the VNA in the National Instrument Measurement and Automation Explorer but I cannot connect it to the DAK software. What should I do?

A: The DAK Software needs VISA drivers in order to communicate with the VNA. When you are installing the NI-488.2 for Windows be sure the NI-VISA Run Time Support and Configuration Support are selected. Some older Agilent ENA or PNA models have a LAN interface which is incompatible with the VISA standards and therefore DAK can only be operated with GPIB-USB adapter.

Q: I don’t find my VNA in the list of supported instruments. What should I do?

A: We are continuously working on the extension of the list. Please let us know what VNA you plan to use. 

Q: How to use the Copper Mountain VNAs in the DAK Software?

A: Install the VNA’s USB driver:

- Connect the Analyzer to your PC via the supplied USB cable. It is allowed to connect the USB cable to the running PC.

- Turn on and boot the PC, if it is off.

- When you connect the Analyzer to the PC for the first time, Windows will automatically detect the new USB device and will open the USB driver installation dialog (Windows 2000/XP/VISTA). In Windows 7 and 8, open the USB driver installation dialog as follows: Start > Control Panel > Device Manager.

Make the right mouse click on the 'Unknown Device' line and select 'Update Drivers'.

- In the USB driver installation dialog, click on 'Browse' and specify the path to the driver files, which are contained in the \DRIVER folder.

- When the driver is installed, the new USB device (PLANAR Network Analyzer) will appear in the system.

The PlanarR140 software is part of the DAK installation package. To install any other VNA program, run the installer file. Follow the instructions of the installation wizard until the program is installed.

Run the software (e.g., Planar804 or PlanarR54) as administrator.

Start the DAK software.

Select Planar 804 or PlanarR54 from the VNA drop down list in the Setup tab.

Make sure that in the VNA settings dialog box the COM server is specified as Planar804 (or R54).

Q: During a measurement I hit the coaxial cable by accident. Is the measurement influenced?

A: Possibly. The DAK measures the complex reflection coefficient, S11, and calculates the permittivity. The S11 phase is sensitive to cable movements. In case the cable was only slightly touched, the "Refresh" function may be sufficient. In general, it is recommended to perform a new calibration (Open/Short/Load) and perform a new measurement.

Q: I immersed the DAK probe in the liquid and now I observe bubbles on the flange. Is there an easy way to remove the bubbles?

A: Yes, you can use simple tools such as disposable cotton swabs to remove the bubbles.

Q: I saw scratches on the probe flange. Is the precision of the probe changed or influenced?

A: It depends on the position of the scratches. If they are close to the perimeter the effect is probably negligible. Take well known reference liquids (ethanol, methanol or water) and perform a measurement. If your measurement reproduces the target values, the effect of the scratch is negligible. The shorting block can scratch the probe flange. If the scratch is on dielectric bead then the performance is most likely influenced. Use reference liquids to verify it. If the probe performance is influenced, please contact us to arrange the repair. We polish the surface and control the performance. The probe is then sent back to you with a new calibration certificate.

Q: How can I obtain precise measurements?

A: Always use pure and uncontaminated liquids e.g. freshly open methanol or de-ionized water. Maintain a stable temperature in the room where the DAK is set up. Measure precisely the temperatures of the liquids. Clean the probe flange before the measurement run, and clean it after each immersion. Keep the coaxial cable in a fixed position. For more detail please refer to Section 4.2 in the DAK Professional Handbook.

Q: Can I use another cable to connect the DAK probe to a VNA?

A: The cable delivered with the probe has excellent phase and amplitude stability. If other cables are used, it could influence the phase stability in therefor the measurement uncertainty.

Q: Is the calibration sequence (Open/Short/Load) important?

A: No. You can freely choose any sequence, Load/Open/Short. The software simply needs three different standards in order to translate the reflection coefficient to the probe flange.

Q: Why is a precise temperature measurement important for the calibration (Load)?

A: The complex dielectric constant is temperature dependent. Let us have an example. The complex dielectric constant of water at 900 MHz at 20 C and 25 C are 80.00 + j*3.94 and 78.20 + j*3.41, respectively. The imaginary part changes more than 10 % between 20 and 25 C. 1 C uncertainty in the temperature measurement results alone 3 % measurement uncertainty in the dielectric constant. For more detail please refer to Section 6.3.1.3 in the DAK Professional Handbook.

Q: What is the best Load material for the calibration?

A: A good measurement practice is to use such a Load material with similar dielectric properties to the sample. In that way we have a well determined curve on the Smith chart, close to the material under test. You can define your own targets in the Dielectric Media menu. Be aware that the precision of the target influences the measurement. The higher uncertainty is in the Load permittivity the lower precision is in the measurement. For more detail please refer to Section 2.5.3.3 in the DAK Professional Handbook.

Q: How can I clean the DAK probe after the measurements?

A: You can use alcohols or other materials for disinfecting. The probe is made of stainless steel, the dielectric bead is ECCOSCTOCK® 0005. For the specification please visit: https://www.laird.com/products/microwave-absorbers/low-loss-dielectrics/eccostock-0005. Note that the bead material is not compatible with Acetone or any other strong solvents. The probe has inner cavities which are open from the connector side which must not be contaminated with liquids, especially not with water.

Q: What kind of materials can I study with the DAK probe?

A: You can study any material that do not damage the probe. The probe is made of stainless steel, the dielectric bead is ECCOSTOCK® 0005. For the specification please visit: https://www.laird.com/products/microwave-absorbers/low-loss-dielectrics/eccostock-0005.