The Insulation Oil Kinematic Viscosity Tester under Wuhan UHV can help many power workers conduct various power tests more conveniently.
In simple terms, its core function is to fully simulate and automate the classic laboratory method for manually measuring viscosity-the capillary method. Through high-precision sensors and computer control, it eliminates human error and achieves efficient and accurate measurement.
1. Preparation and Aspiration
Sample Loading: The operator only needs to place multiple samples to be tested (e.g., in vials or test tubes) onto the instrument's sample tray (or carousel).
Automatic Aspiration: The instrument's robotic arm moves over a clean, empty viscometer U-tube (usually glass). A high-precision, stepper motor-driven aspiration system descends, inserts a pipette into the U-tube, creates a partial vacuum to draw the specified sample from its vial through another pipette precisely into the U-tube's reservoir.
Viscometer Selection: The instrument is often equipped with multiple capillaries of different diameters (corresponding to different constants C) to accommodate samples of varying viscosity ranges. The computer automatically selects the most appropriate viscometer for measurement based on preset sample information or an initial judgment.
2. Temperature Control and Stabilization
Constant Temperature Bath: The entire viscometer U-tube is immersed in a transparent, high-precision constant temperature bath (common temperatures are 40°C and 100°C).
Precise Temperature Control: The bath is filled with a medium like transparent silicone oil or glycol. Through a heating/cooling system, powerful stirrers, and PID intelligent temperature control algorithms, the temperature is maintained stable at the set value (e.g., 40.00°C ± 0.01°C). Any minor fluctuation in temperature can significantly affect the viscosity result, making this the most critical aspect for ensuring accuracy.
3. Measurement and Timing
Sample Positioning: The sample meniscus is precisely raised to a starting bulb above the capillary (above the upper timing mark) by applying suction or pressure.
Free Flow and Automatic Timing: The system then stops aspiration, allowing the sample to flow freely through the capillary under its own gravity.
Photoelectric Detection: Infrared photoelectric sensors are installed at the positions of the upper timing mark and lower timing mark on the capillary. The change in light transmission as the sample meniscus passes these points is accurately detected by the sensors.
Precise Timing: The computer records the time when the meniscus passes the upper mark (t1) and the lower mark (t2), automatically calculating the flow time t = t2 - t1. This process is typically repeated several times (e.g., 2-4 times), and the average is taken to minimize random errors.
4. Cleaning and Drying (Preparing for the Next Sample)
This is key to achieving "fully automatic" and continuous measurement. After one measurement is complete, the instrument does not use the same contaminated viscometer directly for the next sample.
Drain Waste: First, the measured sample is expelled as waste into a designated waste container.
Solvent Rinse: Cleaning solvent (e.g., petroleum ether, toluene, etc., chosen based on the sample properties) is automatically aspirated into the viscometer for multiple rinses to dissolve and remove any residual sample.
Drying: After rinsing, air or an inert gas (like nitrogen) is aspirated to purge the inside of the viscometer, ensuring it is completely dry and clean, free from any solvent or sample residue, guaranteeing the purity of the next measurement.
5. Calculation and Output
Automatic Calculation: The computer automatically calculates the kinematic viscosity value using the formula ν = C × t, based on the measured average flow time t and the pre-stored capillary constant C for that tube.
Result Output: The final result (including viscosity value, flow time, temperature, capillary number, etc.) is automatically displayed on the touchscreen and can be printed via a connected printer or transmitted to a Laboratory Information Management System (LIMS).