Using the Stokes Viscometer

This manual is intended for using the Stokes Viscometer from CIDEPE.

Equipment description

This is formed by,

• a glass tube in which the working fluid is to be filled in,
• a set of metal balls of different diameters and weight,
• there is a rule placed behind the tube so that sensors can be placed at the desired positions,
• an automated system for the measurement of time with programs to calculate the velocity using 5 sensors. This is called multi-chronometer in the original equipment manual.

Notice that the time in the multi-cronometer is given in seconds but the readings use a comma for sepration of decimals.

The sensors are activated by the presence of any object between the light emitter and its receptor. However a transparent fluid in a transparent tube is convenient for this type of measurement.

The multi-chronometer has different functions according to possible ways of calculating the dynamic viscosity. For example, you may instruct the equipment to read the time between sensors or read, directly, the average velocity.

Since the multi-chronometer was designed for several other equipments / experiments not all functions fit viscosity measurements. Therefore, only function F1 2 to 5 sensors is to be used for viscosity measurements.

You may also use the function F11 sensor test in case you suspect malfunction in some of the sensors.

Fig. 01. Stokes viscosimeter from CIDEPE

Setting up the viscosimeter

This operation should be quite easy. Do as follows,

1. fill the tube with a transparent liquid of known density at the working temperature. You may use water or glycerine or some alcohol,
2. next choose the ball you may wish to start making your tests. This is, you may measure viscosity by using balls of different material and size. It would be interesting to discuss the effects of this parameters on your measurements,
3. set-up the multi-chronometer to work with F1 2 to 5 sensors,
4. allow the ball to fall to start the measurements in an automated way,
5. check for your measurements in the menu.

Some comments on F1 2 to 5 sensors

Follow the next pictures to properly get-up and running with this function. You are suppose to have everything else ready.

In the menu choose for function F1.

Fig. 02. Push the center button for ok. and start setting-up this function.

Once accepted, the multi-chronometer will take to another screen asking for the number of sensors: 2 or 5.

Fig. 03. Choose between only two options: 2 or 5 sensors. For this example, only 2 sensor shall be used. Therefore, push the left button.

You should be warned that if one of the sensors is not working the function F1 shall be completely unusable. This is due to the programming of the multichronometer.

Once the number of working sensors is selected you will be asked to introduce the vertical distance between the sensors, if you are only using two sensors, or the distance of each sensor from the highest one, if you are using 5 sensors.

Fig. 04. You are asked if you wish to introduce the distance. Since, we are looking for velocity measurements, distances should be introduced.

Fig. 05. You should use the 4 buttons in the right to introduce the distance between sensors. Use the up and down buttons to change between 0 and 9, and the left and right buttons to change between number positions.

For this purpose the equipment also provides a rule attached behind the galss tube.

Fig. 06. Rule to measure the distance between the sensors in the CIDEPE Stokes viscosimeter.

For the present case, the distance between the sensors was 210 mm. This is shown below.

Fig. 07. Set distance between the first and last sensor.

Once this is done, as shown in Fig. 7, the button for ok is pushed. We are almost done.

The program then asks you if you want to start the experiment.

Fig. 08. If you want to start the measurements then you should throw the ball into the fluid. Next, the program will start taking time measurements.

The program starts reading automatically once the ball falls through the fluid and passes across all sensors to the end. Also the program stops automatically once the ball has passed the last sensor.

Results are presented in a furthr screen. Actually, the program asks you if you want to see the results or repeat the experiment.

Fig. 09. Once the experiment is finished you are prompted as shown above. Do you wanst to see the results or repeat the measurements?

Fig. 10. Results screen.

Fig. 11. In this screen the average velocity is presented.

Next, a short video showing some steps of the usage for average velocity measurements is presented.

Any question? Write in the comments and I shall try to help.

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Ildebrando