Viscometer

Viscosity, a measure of a fluid’s resistance to flow, is a critical parameter in countless industries, from pharmaceuticals and food production to coatings and chemicals. Selecting the appropriate viscometer is essential for accurate quality control, research, and development. HINOTEK offers a range of digital viscometers designed for reliability and ease of use. This guide will help you navigate the key considerations to choose the perfect HINOTEK viscometer for your specific application.

Before choosing a viscometer, it’s helpful to understand the basics:
Viscosity: Simply put, it’s the thickness or internal friction of a fluid. Water has low viscosity, while honey has high viscosity.
Newtonian Fluids: These fluids have a constant viscosity regardless of the shear rate applied (e.g., water, oils, simple solvents). Their viscosity mainly depends on temperature.
Non-Newtonian Fluids: Their viscosity changes depending on the applied shear rate or stress (e.g., ketchup, paint, polymers, slurries). Some become thinner with shearing (shear-thinning), while others thicken (shear-thickening). Some also exhibit time-dependent behavior (thixotropy).
Knowing whether your sample is Newtonian or non-Newtonian is crucial, as it influences the type of viscometer and testing parameters needed.

Consider these critical factors when evaluating viscometers, including those from HINOTEK:
Viscosity Range: What is the expected minimum and maximum viscosity of your samples (measured in mPa·s or cP)? Ensure the viscometer’s measurement range covers your needs. HINOTEK models offer different ranges (e.g., RV-SSR-H up to 4M mPa·s, HB-SSR-H up to 16M mPa·s, with optional rotors extending ranges).
Sample Type & Characteristics: Are you measuring liquids, pastes, slurries, or gels? Consider particle size, potential for settling, or chemical compatibility (requiring specific materials like stainless steel).
Sample Volume: How much sample do you typically have available for testing? Some techniques require larger volumes, while others, like HINOTEK’s high-temperature models using small sample adapters, need only 15-20 ml.
Temperature Requirements: Viscosity is highly temperature-dependent. Do you need to measure at ambient temperature, or control it precisely at specific elevated temperatures? HINOTEK offers models with standard heating baths and high-temperature options (e.g., up to 250°C or even 300°C). Accurate temperature control (like ±0.1°C in some HINOTEK models) is vital.
Shear Rate Requirements: For non-Newtonian fluids, understanding behavior at different shear rates is often necessary. Rotational viscometers, like those offered by HINOTEK, allow testing at various speeds (shear rates). HINOTEK models like RV-SSR-H and HB-SSR-H offer multiple speed settings (e.g., 18 speeds).
Accuracy and Repeatability: What level of precision do you require? Check the manufacturer’s specifications for accuracy (e.g., ±3% for Newtonian liquids in HINOTEK high-temp models) and repeatability (e.g., ±1.5%).
Ease of Use and Cleaning: Consider the user interface (HINOTEK models feature LCD displays showing direct readings), setup time, and how easy the instrument is to clean between samples, especially if testing different materials.
Data Output & Connectivity: Do you need to print results or connect to a PC? Some HINOTEK models offer RS232 interfaces for direct connection to printers or computers (optional software may be available for rheological curves).
Application Goal: Are you performing routine quality control (QC) checks or more in-depth research and development (R&D) requiring detailed characterization?

For rotational viscometers, selecting the correct spindle is critical for accurate measurements within the instrument’s range.
General Rule: Lower viscosity fluids typically require larger spindles or higher speeds, while higher viscosity fluids need smaller spindles or lower speeds.
Target Range: Aim for a spindle/speed combination that gives a torque reading within the optimal range recommended by the manufacturer (often between 10% and 90-100% of the full-scale range) for best accuracy.
HINOTEK Spindles: High-temperature models typically come with standard spindles (e.g., #21, #27, #28, #29). An optional #0 rotor is often available to measure lower viscosity ranges. Refer to the specific model’s manual for guidance on spindle selection based on the expected viscosity range.

To choose the best HINOTEK viscometer:
Define Your Needs: Clearly list your requirements based on the factors discussed above (viscosity range, sample type, temperature, volume, accuracy, etc.).
Review HINOTEK Models: Compare the specifications of different HINOTEK digital viscometers available on their website or in catalogs against your requirements. Pay attention to measurement ranges, temperature capabilities, and included accessories.
Consider High-Temperature Needs: If your application involves hot melts, asphalt, waxes, or other high-temperature materials, focus on models like the RV-SSR-H, HA-SSR-H, or HB-SSR-H.
Consult with Experts: Don’t hesitate to contact HINOTEK or an authorized distributor. Provide them with your application details, and they can offer specific model recommendations and advice on appropriate configurations (including spindles).
Conclusion
Choosing the right viscometer is a crucial step towards obtaining reliable and meaningful viscosity data. By carefully considering your sample characteristics, testing conditions, and application goals, and understanding the features offered by HINOTEK’s range of digital rotational viscometers, you can select an instrument that provides accurate results and enhances your laboratory’s capabilities. Always refer to the specific product documentation and consult with HINOTEK experts when making your final selection.

Conversion between viscosity units

1 cP = 1 mPa·s ;  1 P = 100 cP;  1 Pa·s = 1000 mPa·s;  P = poise;  1 Pa·s = 10 poise
1 M mPa·s = 1,000,000 mPa·s;  1 dPa·s = 100 mPa·s
1 Pa·s = 1000 cP = 1000 mPa·s = 10 P = 10 dPa·s

The conversion formula between dynamic viscosity (η) and kinematic viscosity (ν) is:
ν = η / ρ
where:

• ν = kinematic viscosity (m²/s or Stokes, St)
• η = dynamic viscosity (Pa·s or Poise, P)
• ρ = fluid density (kg/m³ or g/cm³)

Common Units:

• Dynamic viscosity (η): Pa·s (SI unit), cP (centipoise, 1 cP = 0.001 Pa·s)
• Kinematic viscosity (ν): m²/s (SI unit), cSt (centistokes, 1 cSt = 10⁻⁶ m²/s)

For example, if a liquid has a dynamic viscosity of 100 cP (0.1 Pa·s) and a density of 1000 kg/m³, its kinematic viscosity is:
ν = 0.1 / 1000 = 0.0001 m²/s (or 100 cSt).

Classification of fluids:

Fluids can be divided into Newtonian fluids and non-Newtonian fluids. Newtonian fluid refers to a fluid whose viscosity does not change with shear rate, but remains constant. Any fluid whose viscosity changes with rotating speed or shear rate is a non-Newtonian fluid. Non-Newtonian fluids are divided into two categories:

1. Fluids whose viscosity changes only with changes of shear rate.
2. Fluids whose viscosity changes with the change of shear rate and the extension of measurement time.

Viscosity of common fluids:

Viscosity refers to the fluidity (or illiquidity) of a substance. Its measurement unit is centipoise. The viscosity of water is 1 centipoise and it flows very easily.

• 1 cps = water
• 3.2 cps = milk
• 16.5 cps = cream
• 34.6 cps = vegetable oil
• 176 cps = tomato sauce
• 880 cps = glycerin
• 1760 cps = molasses
• 3000 cps = glue
• 8640 cps = syrup B
• 15200 cps = sour cream

Kinematic viscosity is the ratio of the dynamic viscosity of the liquid to the density (p) of the fluid under the same temperature. The unit is m²/s. Use the lowercase letter “v” to indicate.

Note: The unit used in the past is St (Stokes). The relationship between St (s) and m²/s is:
1 m²/s = 10⁴ St = 10⁶ cSt (“cSt” is pronounced “Cist”).