Contact angle goniometer buyer's guide
How to Read a Contact Angle Goniometer Datasheet: 11 Questions
A goniometer datasheet is only useful if it separates accuracy from resolution, names what the accuracy was measured against and prices the software. Of six entry systems checked on 25 October 2026, KRÜSS prints the most complete sheet but sells by quote. The Dropometer, US$4,990, names its accuracy reference but has gaps we list below.
What does a goniometer datasheet usually leave out?
Most datasheets print a camera resolution, a contact angle range and a resolution in degrees. Fewer print the three things that decide whether two labs will agree: an accuracy figure separate from resolution, what that accuracy was measured against, and how the baseline is found.
Resolution is the smallest step the software displays. Accuracy is how close the reading is to the true value. The international metrology vocabulary treats them as different properties, and a goniometer can display 0.01° while being off by a degree or more. Vuckovac and colleagues showed that more image pixels alone do not guarantee a more accurate angle, and that moving the baseline by one pixel shifts the angle by about 0.5° to 1° on most surfaces.
The 11 questions below follow the 11 criteria we score in the under US$5,000 buying guide. Each one names a gap, explains why it moves your result, and gives the exact question to send.
What six entry systems publish, checked 25 October 2026
<p>Values as printed by each maker on its product page or datasheet. DataPhysics figures are from the OCA series datasheet because the OCA 15EC page did not load. "NP" means not published.</p>
| Datasheet item | Dropometer | Ossila | ramé-hart Model 190 | KRÜSS DSA25 | DataPhysics OCA 15EC | Biolin Scientific Theta Lite |
|---|---|---|---|---|---|---|
| Contact angle range | 10° to 175° | 5° to 180° | NP | 0° to 180° | 0° to 180° | 0° to 180° |
| Contact angle accuracy | 0.35° | ±1° | NP | 0.1° | ±0.1° | ±0.1° |
| Accuracy reference named | Yes: KRÜSS DSA100E, peer reviewed | NP | NP | NP | NP | NP |
| Resolution printed separately from accuracy | Same table cell | Resolution NP | NP | Yes, labelled | Yes, separate rows | Resolution NP |
| Surface tension range | Up to 75 mN/m | Offered; range NP | NP | 0.01 to 2,000 mN/m | 0.01 to 2,000 mN/m | 0.01 to 2,000 mN/m |
| Camera frame rate | NP | 30 fps | 520 fps | Up to 2,300 fps | 227 fps (higher at reduced window) | 2,347 fps |
| Field of view | NP | NP | NP | 3.2 to 18.5 mm | 1.11 to 7.14 mm wide | 2.3 to 7.8 mm |
| Smallest dosed drop | 0.05 µL (auto dropper) | NP | Dispenser step 0.02 µL (option) | NP (20 nL resolution) | NP | Down to 0.1 µL |
| Baseline detection | Automatic (sessile) | NP | NP | NP | Automatic | Automatic |
| Software licence | Lifetime, unlimited users | Free software; terms NP | NP | NP; some modules optional | NP; some modules optional | All inclusive, unlimited licences |
| Temperature control | Upgrade; specs NP | NP | Heated and Peltier options | −30 °C to 400 °C by chamber | Chambers listed for the series | Chambers to 110 °C |
| Warranty | 5 years | 2 years | 1 year, extendable | NP for new units | NP | NP |
Questions 1 to 4: what it measures and how well
1. Measurement scope
What the datasheet often leaves out: which methods are in the base price and which are separate software modules or hardware options; the usable contact angle range at the extremes.
Why it changes your number: a surface free energy or sliding angle result you assumed was included may need a module you did not budget for, and readings near 0° or 180° sit where fitting is least reliable.
Ask the vendor: "Which measurements are included in this quoted price, which need extra modules, and what is the contact angle range for each fitting method?"
2. Published accuracy
What the datasheet often leaves out: an accuracy figure separate from resolution, and the reference it was measured against. Only one of the six systems above names a reference, and none describes its test method on the datasheet.
Why it changes your number: a 0.01° resolution says nothing about whether the reading is right. If two instruments are off in different directions, two labs will disagree on the same sample.
Ask the vendor: "What is the contact angle accuracy, separate from display resolution, what reference sample or instrument was it measured against, and where is that published?"
3. Operator independence
What the datasheet often leaves out: whether the baseline and drop edge are found automatically, and what happens when the operator moves them.
Why it changes your number: baseline placement is one of the largest sources of operator error. Vuckovac and colleagues found that analysing the same image can give results up to 10° apart.
Ask the vendor: "Is the baseline found automatically on every image, can the operator override it, and is the override recorded with the result?"
4. Optics and image quality
What the datasheet often leaves out: field of view, magnification and frame rate, as opposed to camera megapixels.
Why it changes your number: a drop that fills too little of the frame has fewer edge pixels to fit, and a slow camera cannot capture fast spreading or advancing and receding angles cleanly.
Ask the vendor: "What field of view and frame rate do you get at the drop size we will use, and is the optics telecentric?"
Expert Quote
Not all contact-angle measurements are created equal: the right method depends on the application. A sessile drop and a tilted plate can give very different, and equally correct, numbers.
Questions 5 to 8: time, upgrades, records and cost
5. Time per sample and dosing
What the datasheet often leaves out: the smallest drop the dosing system places reliably, its volume resolution, and whether dosing is manual or automatic.
Why it changes your number: drop volume changes the measured angle. Huhtamäki and colleagues recommend 3 to 10 µL: smaller drops are disturbed by the needle and larger ones are flattened by gravity.
Ask the vendor: "What drop volume does your dosing system place repeatably, at what resolution, and how long does one measurement take from drop to saved result?"
6. Upgrade path
What the datasheet often leaves out: which options can be added to the instrument you buy today, and which need a different model.
Why it changes your number: it decides whether a new method next year is an option purchase or a second instrument, which changes the five year cost.
Ask the vendor: "Which hardware and software options can be added to this exact model later, and at what list price?"
7. Records
What the datasheet often leaves out: whether raw images are saved with every result so a reading can be rechecked later.
Why it changes your number: a number without its image cannot be reanalysed when a customer or reviewer questions it.
Ask the vendor: "Does the instrument save the raw image and fit with every result, and can an old result be reanalysed in a newer software version?"
8. Five year cost of ownership
What the datasheet often leaves out: software licence terms after year one, service and calibration pricing, and consumables.
Why it changes your number: a lower purchase price with a yearly licence or a service contract can cost more by year five. Our cost guide walks through a five year worksheet.
Ask the vendor: "What will we pay in years two to five for software, service, calibration and consumables?"
Questions 9 to 11: setup, warranty and platform
9. Portability and setup
What the datasheet often leaves out: power needs, footprint, whether a separate computer is needed, and realistic setup time.
Why it changes your number: an instrument that needs a dedicated bench and PC will not move between labs or onto a line, so samples queue for it instead.
Ask the vendor: "What does the instrument need to run (mains, battery, PC), what is its footprint, and how long does setup take after moving it?"
10. Warranty
What the datasheet often leaves out: the warranty length for new units and what it excludes. Three of the six makers above publish no warranty for new instruments.
Why it changes your number: repairs outside warranty go straight into your five year cost.
Ask the vendor: "How long is the warranty on a new unit, what does it exclude, and what does an out of warranty repair typically cost?"
11. Software and platform
What the datasheet often leaves out: the operating system and computer the software needs, who owns the licence, and whether it runs offline.
Why it changes your number: an operating system update or a locked down network can stop measurements if the software needs a specific PC or an internet check.
Ask the vendor: "Which operating system and hardware does the software need, is the licence tied to a device or user, and does it work fully offline?"
The vendor email: all 11 questions in one list
Copy this list into one email and send the same version to every vendor. Put the answers side by side before you compare prices.
- Which measurements are included in this quoted price, which need extra modules, and what is the contact angle range for each fitting method?
- What is the contact angle accuracy, separate from display resolution, what was it measured against, and where is that published?
- Is the baseline found automatically on every image, can the operator override it, and is the override recorded?
- What field of view and frame rate do you get at our drop size, and is the optics telecentric?
- What drop volume does the dosing system place repeatably, at what resolution, and how long does one measurement take?
- Which options can be added to this exact model later, and at what list price?
- Does the instrument save the raw image and fit with every result, and can old results be reanalysed?
- What will we pay in years two to five for software, service, calibration and consumables?
- What does the instrument need to run, what is its footprint, and how long does setup take after moving it?
- How long is the warranty on a new unit, and what does it exclude?
- Which operating system and hardware does the software need, how is the licence tied, and does it work fully offline?
Who should not buy a Dropometer?
Our own datasheet has gaps too. The Dropometer is the wrong choice if any of these matter to you.
- You need a published frame rate or high speed video. We do not publish a frame rate; KRÜSS, DataPhysics and Biolin Scientific publish rates in the thousands of frames per second.
- You need surface tension above 75 mN/m. That is the top of our published pendant drop range; several benchtop systems publish ranges up to 2,000 mN/m.
- Your surfaces sit below 10° or above 175°. That is outside our published contact angle range.
- You need the tightest published accuracy. Three benchtop makers above publish 0.1°; we publish 0.35°.
- You need a temperature specification. Environmental control is an upgrade and we do not yet publish its range.
- You need audit trails or electronic signatures. The Dropometer does not support them.
Where can you go deeper?
- Contact angle goniometers: buying guide hub
- Best contact angle goniometer under US$5,000, scored on the same 11 criteria
- Best for advanced research and best for ISO and GLP regulated QC
- Dropometer vs KRÜSS DSA100 and DSA25, Dropometer vs DataPhysics OCA and Dropometer vs Ossila
- Contact angle measurement guide, Young Laplace equation and contact angle hysteresis
- ASTM D7334 for advancing contact angle and ISO 19403-2 for surface free energy
- The two peer reviewed validation papers
About this guide. Droplet Lab makes the Dropometer. Each entry in the table is what the maker publishes on its own product page or datasheet, checked on 25 October 2026; "Not published" means we could not find it there, not that the instrument lacks it. Makers update datasheets, so check the current version before you order. This guide was drafted with Claude Opus 5.5 and reviewed by Droplet Lab.
Send us a datasheet and we will mark the gaps
Book a 15 minute call with the datasheet or quote you are weighing; we will point out what it does not tell you, whoever makes the instrument.
Frequently Asked Questions
What is the difference between accuracy and resolution on a goniometer datasheet?
Resolution is the smallest step the software displays, for example 0.01°. Accuracy is how close the reading is to the true value, for example 0.35°. A datasheet that prints only resolution has not told you how accurate the instrument is.
What drop volume should I use for contact angle?
A widely cited protocol by Huhtamäki and colleagues (Nature Protocols, 2018) recommends 3 to 10 µL. Smaller drops are disturbed by the needle, and larger drops are flattened by gravity. Use the same volume every time so results compare.
Why do two goniometers give different contact angles on the same sample?
Differences in baseline placement, drop volume, fitting method and timing are the usual causes. Moving the baseline by a single pixel can shift the angle by about 0.5° to 1°, and the same image analysed differently can give results up to 10° apart.
Does a higher frame rate make a goniometer more accurate?
Not for a static drop at rest. Frame rate matters when the drop is moving, for example fast spreading, drop impact or advancing and receding angles measured while the edge moves.
Is the Dropometer's 0.01° figure its accuracy?
No. 0.01° is the display resolution. The published accuracy is 0.35°, from side by side measurements against a KRÜSS DSA100E in peer reviewed papers.
Which standard covers advancing contact angle measurement?
ASTM D7334 covers advancing contact angle on coatings, substrates and pigments. ISO 19403-2 covers surface free energy from contact angle measurements.