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Frequently Asked Questions

For more information, please select a topic from the list below.

  • How do I know if my instrument is within Calibration? +


    To determine if your instrument is within calibration, follow these steps:
    1. Check Calibration Due Date: Most instruments come with a calibration certificate that indicates the date of the last calibration and when the next calibration is due. Make sure to check the calibration sticker or documentation to see if it's within the specified period.

    2. Reference to Manufacturer Specifications: Compare the instrument’s performance with the manufacturer's specifications. If it's behaving as expected within the specified tolerance ranges, it’s likely within Calibration.

    3. Perform a Calibration Check:
      • Use standard reference materials or solutions that have known values. For example, if you’re working with a viscometer, you could use a viscosity standard fluid with a certified value.
      • Test the instrument with the standard and compare the reading. If the readings match the known values within an acceptable tolerance, the instrument is likely still in calibration.

    4. Environmental Factors: Ensure the instrument has been used under the correct environmental conditions (temperature, humidity, etc.), as deviations from these can affect calibration.

    5. Annual or Routine Calibration Schedule: Instruments, especially precision ones like viscometers, rheometers, or moisture analyzers, are typically calibrated annually. If it's been more than a year, or if the instrument has undergone heavy usage or a severe shock (e.g., being dropped), it may require recalibration even if it's within the usual interval.
      6. If you're unsure or if you notice any drift in measurements, it's a good idea to send the instrument back for recalibration by the manufacturer or a certified calibration service.

  • How is the accuracy of a CAP Viscometer calculated? +


    The accuracy of an AMETEK Brookfield CAP viscometer is determined by two factors: the accuracy of the instrument and the accuracy of the calibration fluid. The total accuracy is the sum of both.
    • Instrument Accuracy: Consult Table 3.1 in the CAP viscometer manual to find the percentage of full-scale range (FSR) that applies to your specific CAP model and spindle. For example, a CAP 1000H with cone spindle 3 at 900 RPM has a full-scale range of 8.333 Poise, and the instrument accuracy would be 2% of FSR.

    • Fluid Accuracy: The accuracy of the calibration fluid is typically 1% of its value. For instance, if the calibration fluid is 4 Poise, fluid accuracy would be 0.04 Poise.
    To calculate total accuracy:
    Instrument accuracy + fluid accuracy = total accuracy. For example, if the instrument accuracy is 0.17 Poise and the fluid accuracy is 0.04 Poise, the total accuracy would be 0.21 Poise.

  • How do I calculate the accuracy of the reading when testing a sample? +


    To calculate the accuracy during sample testing, use 1% of the full-scale range (FSR). You can determine FSR by pressing the AUTO RANGE button on your digital viscometer. The FSR value is the highest achievable viscosity reading for the spindle and speed selected. Once you have the FSR, 1% of this value represents the instrument accuracy.

    For dial viscometers, multiply your factor by 100 to get the FSR and calculate accuracy accordingly.

  • How do I choose a spindle and speed? +


    • If the viscosity of your fluid is known: The maximum viscosity range for a spindle at a given speed is the spindle factor multiplied by 100. The minimum viscosity is 10 times the factor. Knowing this range helps determine whether the fluid fits within the capabilities of that spindle/speed combination.

    • If the viscosity of your fluid is unknown: Start by selecting a speed and spindle that produce readings between 10% and 100% torque. If the reading is below 10% or above 100%, adjust the speed or switch to a different spindle until you achieve readings within the desired range.
    For digital viscometers, the AUTO RANGE feature simplifies this process by automatically calculating and displaying the full-scale range for the selected spindle and speed.

  • How is viscosity affected by temperature? +


    Viscosity decreases as temperature increases. This inverse relationship makes temperature control critical during viscosity measurements. Ensure the sample, spindle, and container are all at thermal equilibrium to obtain accurate results.

  • How long should I wait for thermal equilibrium? +


    The time required for thermal equilibrium depends on the viscosity of the sample. For silicones:
    • 5 - 500 cP: Wait 1 hour.
    • 1,000 - 12,500 cP: Wait 2 hours.
    • 30,000 - 100,000 cP: Wait 4 hours.
    For accessories like the CAP, Cone/Plate, and Small Sample Adapter (SSA), wait 10-20 minutes depending on the volume.

  • How many viscosity standards do I need? +


    One or two viscosity standards are usually sufficient. Select a standard fluid that fits within the measuring range of the spindle and speed you use most frequently.

  • Why is my digital viscometer displaying "EEEEE"? +


    The "EEEEE" error means the reading is over-range, indicating the viscosity exceeds the full-scale range for the selected spindle and speed. Lower the speed or switch to a different spindle to raise the full-scale range.

  • Why won’t my dial reading or viscosity (cP) value stabilize? +


    This typically occurs with non-Newtonian fluids, which do not have a constant viscosity. For more information on Newtonian and non-Newtonian behavior, consult Brookfield's publication More Solutions to Sticky Problems.

  • Why is my spindle wobbling during rotation? +


    A wobbling spindle may be bent. Compare the spindle’s straightness to the dimensions in Appendix A of More Solutions to Sticky Problems. Additionally, check for wear or damage in the jewel bearing or pivot point. If necessary, recalibrate or service the viscometer.

  • Should I use a digital or dial-reading viscometer? +


    Both digital and dial-reading viscometers provide accurate and reproducible viscosity readings. As long as the same conditions (spindle, speed, temperature, etc.) are used, results from both types of viscometers are equally valid.

  • Should I use silicone or mineral oil viscosity standards? +


    The choice depends on your product. Silicone is more commonly used because it is less temperature-sensitive. However, industries like paint manufacturing, which avoid silicone contamination, should use mineral oil standards.

  • What should I do if my fluid's viscosity is not part of the standard fluids list? +


    Typically, the specific viscosity of your sample is not crucial for calibration checks, as Brookfield Viscosity Standards are non-shear dependent. If your viscometer passes calibration at one range, it can be considered accurate across its entire range.

  • What is a math model, and when should I use it to evaluate viscosity test data? +


    Math models are empirically developed to fit trends in viscosity data. The most appropriate model depends on your sample type. Brookfield software, such as Rheocalc and Wingather, offers tools for curve fitting, helping you choose the best model for analyzing your data.

  • How is viscosity affected by temperature? +


    Brookfield instruments are accurate to +/- 1 °C up to 150 °C, and +/- 2 °C above 150 °C. This accuracy applies to viscometers with RTDs and temperature probes, ensuring reliable results during testing.

  • How do I verify that my instrument is calibrated? +


    Use a Brookfield Viscosity Standard Fluid at three different rotational speeds to verify the instrument’s response across low, medium, and high torques. For example, an RV viscometer with an RV #3 spindle can be tested at 20, 10, and 5 RPM using a 5,000 cP fluid.

  • Why do I need a viscosity standard? +


    Viscosity standards ensure the accuracy of your Brookfield viscometer. Standards, such as silicone or mineral oil, provide a stable viscosity value at 25°C, simplifying calibration verification and ensuring compliance with certifying bodies like ISO.

  • Can PG Flash be used with my computer? +


    PG Flash is designed for downloading programs to the viscometer. To acquire data on a PC, use Rheocalc-T with DV2T or DV3T viscometers.