A single broadband method for liquids and lossy materials. Using the SPEAG DAK-TL2 open-ended coaxial probe with a Keysight PNA-X or Rohde & Schwarz ZVA 67 vector network analyzer, depending on the band, the Intelligent Electromagnetic Sensor Laboratories (iEMSL) measures dielectric constant (Dk) and loss tangent (Df) from 4 MHz to 67 GHz on solids, semi-solids, liquids and powders, at room temperature.
Available now. The instrument is commissioned and in service.
4 MHz – 67 GHz
One measurement chain
Dk 1 to 800
Df 0.001 to 10
Solids and liquids
Returned to you
5 business days
Standard turnaround
Why the DAK-TL2 coaxial probe
An open-ended coaxial probe is pressed against a sample, or immersed in a liquid, and permittivity is derived from the reflection at the probe aperture. That gives it two things no resonator at iEMSL can offer: continuous coverage from 4 MHz to 67 GHz in one measurement chain, and the ability to measure liquids, semi-solids and powders at all.
It is the right method for medium and high loss materials: absorbers, composites, biological tissue simulants, solvents, gels and slurries. It is the wrong method for low-loss laminates. Because permittivity comes from a reflection measurement, a small loss is only a small perturbation on the result, whereas a resonator measures loss from a Q factor and is far more sensitive to it. Below a Df of 0.001 the probe is outside its stated range, and the FPOR is the method to use instead.
Applications
The service measures complex permittivity, reported as dielectric constant (Dk) and dissipation factor or loss tangent (Df), on non-hazardous liquids across RF and microwave frequencies. Applications include food and beverage testing, covering wine, beer, juices, dairy products and other liquid formulations, as well as transformer oils, lubricants, dielectric coolants, heat-transfer fluids, pharmaceutical formulations and specialty chemicals.
Accurate liquid dielectric property measurements help engineers and researchers understand RF and microwave energy absorption, optimize microwave heating and processing, develop RF sensors, characterize insulating and cooling fluids, validate electromagnetic simulations, and compare material formulations.
One caution on insulating fluids. A clean transformer oil or dielectric coolant is engineered for low loss and can sit at or below the probe’s Df floor of 0.001, where a reflection measurement has little to work with. Dk stays dependable there, Df does not, and because no resonator at iEMSL accepts a liquid there is no method to fall back on. Aged, wet or contaminated fluid, usually the interesting case, sits comfortably inside range. Send the Safety Data Sheet and tell us what you need to learn, and we will say before you ship whether the measurement can answer it.
Technical specifications
| Frequency range | 4 MHz – 67 GHz |
|---|---|
| Dk range | 1 to 800 |
| Df range | 0.001 to 10 |
| Accuracy | Typically better than 3% |
| Repeatability | Typically ±1% |
| Sample states | Solid, semi-solid layer, liquid, powder |
| Temperature | Room temperature only |
| Instruments | SPEAG DAK-TL2 probe with a Keysight PNA-X or Rohde & Schwarz ZVA 67 vector network analyzer, selected by band |
Sample requirements
The probe reads a field that spreads sideways as well as downward, so a sample narrower than the aperture reads its own edge instead of the material. Diameter matters more than most people expect.
- Solids and semi-solids: diameter > 68 mm below 200 MHz, or > 48 mm above 200 MHz
- Layer thickness: 0.1 to 10 mm
- Liquids: 10 to 50 mL per sample, in any container a syringe can draw from. We transfer the sample into the DAK-TL2 measurement vessel at the lab
- Surface: flat and smooth, so the probe face makes full contact with no air gap
Liquid sample safety policy
For Dk/Df testing, we only accept liquids that can be safely handled in a standard RF laboratory using normal PPE and without a chemical fume hood.
An SDS must be provided for all liquid samples. We do not accept liquids that are corrosive, acutely toxic by inhalation, highly volatile, reactive, or that require specialized ventilation or respiratory protection. Final acceptance is subject to SDS review by our laboratory.
What to send us
- Your samples, meeting the diameter, thickness or volume above
- The frequency bands you need, since each band is measured and quoted separately
- Whether each sample is a solid, a semi-solid layer, a liquid or a powder
- A Safety Data Sheet for every material involved
- Expected Dk and Df, if you have an estimate
Pricing
$400 per sample per band
For solids. Liquids, semi-solids and powders are $600 per sample per band, which covers the additional handling and the return shipment. Standard turnaround 5 business days from the day your samples arrive, with rush service available.
Pricing is per band because each band is a separate calibration and measurement. Choosing the bands that matter to your design costs a fraction of sweeping the full range.
Texas A&M researchers receive 50% off listed prices.
Available frequency bands
Pick only the bands your design needs. Each is priced separately.
- 4–600 MHz
- 600 MHz – 1 GHz
- 1–10 GHz
- 10–20 GHz
- 20–30 GHz
- 30–40 GHz
- 40–50 GHz
- 50–60 GHz
- 60–67 GHz
What you receive
- Dk and Df across each band you requested
- Raw data in CSV
- Technical Report on request (for extra charge)
- Your samples back, liquids included. Nothing is disposed of at the lab
View our example measurements. See also: WR-90, SPDR, FPOR, parallel plate, all material characterization services.
Frequently Asked Questions
Can you measure my low-loss laminate with the probe?
No, and we would rather say so than sell you a number you cannot use. Below a Df of 0.001 the probe is outside its stated range. An open-ended coaxial probe derives permittivity from a reflection measurement, where a small loss is only a small perturbation. A resonator measures loss from a Q factor and is far more sensitive to it. Use the FPOR for 10.2 to 52.2 GHz, or the SPDR at 10 GHz.
How much liquid do you need, and do I get it back?
Between 10 and 50 mL per sample, in any container a syringe can draw from. We draw the sample here and transfer it into the DAK-TL2 measurement vessel, so the container you ship in does not have to suit the probe. All liquid samples are returned to you. Nothing is disposed of at the lab. Send a Safety Data Sheet for every material before shipping.
Why does my sample have to be so wide?
The probe reads a field that spreads sideways as well as downward. A sample narrower than that field reads its own edge instead of the material, which biases the result. Solids need a diameter over 68 mm below 200 MHz, and over 48 mm above 200 MHz.
Do I have to pay for the whole 4 MHz to 67 GHz range?
No. Measurement is quoted per sample per band, and there are nine bands. Most projects need one or two. Tell us the frequencies your design operates at and we will quote only those bands.
Can you measure at elevated temperature?
Not with this method. The DAK-TL2 service is offered at room temperature only. The SPDR is the iEMSL method offered up to 100 °C, at a single frequency of 10 GHz.
How does this compare with the high-temperature Keysight probe?
They are the same class of instrument, an open-ended coaxial probe reading permittivity from the reflection at its aperture. The difference is what each one is built to cover, and the honest answer is that each wins on a different axis.
Frequency. The DAK-TL2 covers 4 MHz to 67 GHz. The Keysight N1501A kit spans 200 MHz to 50 GHz depending on the probe fitted. If your material has to be characterized below 200 MHz or above 50 GHz, the DAK-TL2 reaches where that kit does not, and it does so without changing measurement method partway up the band.
Loss. The DAK-TL2 is specified down to a Df of 0.001, which takes it further into moderately low-loss territory than a probe is usually credited with. It is still not the tool for a low-loss microwave laminate, where a resonator measuring from a Q factor will always be more sensitive. For those, use the FPOR.
Temperature. This is where the Keysight high-temperature probe wins outright. It is rated from -40 °C to +200 °C, so it is the right tool when the measurement itself has to happen hot or cold. The DAK-TL2 service at iEMSL is room temperature only. If you need permittivity versus temperature, the SPDR is the iEMSL method that goes to 100 °C, at a single frequency of 10 GHz.
Which standard does an open-ended coaxial probe measurement follow?
No single formal standard covers it. Open-ended coaxial probe permittivity is not standardised the way parallel plate measurement is by ASTM D150 or X-band waveguide by ASTM D5568-22a; the probe geometry and the extraction algorithm vary between manufacturers. What governs the result here is the instrument: the accuracy and repeatability figures in the specification table above, typically better than 3% and ±1%, are SPEAG’s published figures for the DAK-TL2. If your specification requires a named standard, say so when you request a quote. Three iEMSL methods carry one: the parallel plate (ASTM D150, 10 kHz to 10 MHz), WR-90 (ASTM D5568-22a, 8.2 to 12.4 GHz) and the SPDR (IPC 2.5.5.15 and IEC 61189-2-721, 10 GHz). The DAK-TL2 and the FPOR carry none.
Can you handle ITAR-controlled or export-controlled work?
Yes. iEMSL accepts ITAR-controlled projects under a Technology Control Plan, administered with the Texas A&M export control office. Tell us your control requirements when you request a quote, before shipping any samples.
Measuring a liquid, a gel or a lossy composite?
Tell us the material and the frequencies that matter, and we will quote the bands you need.