Talk:Viscometer

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can someone help me fix up the references? --Onionmon 22:27, 28 June 2006 (UTC)[reply]

Vibrating element sensors also employ the bandwidth measurement e.g. Mobrey's 7827 and 7829 tuning fork viscometers and VAF's Viscosense viscometers. In these instruments the sensor is vibrated not at the resonant frequency but alternately at the upper and lower 1/2power points (+/-3 dB)by the expedient of driving out of phase (90deg on either side) The difference in frequency is the bandwidth which is a function of viscosity. It should be pointed out that vibrating element viscometers measure the dynamic viscosity and not kinematic. The Mobrey, Sofraser and TDC sensors all displace fluid and thus in each case the resonant frequency changes with density and thus potentially can derive the kinematic viscosity. Torsional viscometers such as VAF's Viscosense, Nametre Hydramotion etc do not displace the fluid thus the resonant frequency is a function only of the mass of the sensor. MeyerMeyer 15:07, 29 June 2007 (UTC)[reply]

I removed the following material:

Vibrating viscometers are rugged industrial systems used to measure viscosity in the process condition. The active part of the sensor is a vibrating rod. The vibration amplitude varies according to the viscosity of the fluid in which the rod is immersed. These viscosity meters are suitable for measuring clogging fluid and high-viscosity fluids even with fibers (up to 1,000,000 cP). Currently, many industries around the world consider these viscometers as the most efficient system to measure viscosity of any fluid, contrasted to rotational viscometers, which require more maintenance, inability to measure clogging fluid, and frequent calibration after intensive use. Vibrating viscometers has no moving parts, no weak parts and the sensitive part is very small. Actually even the very basic or acid fluid can be measured by adding a special coating or by changing the material of the sensor such as 316L, SUS316, Hastelloy, enamel etc... + - Some companies have devices based on vibrating blades or other vessels, following the original designs patented by SOFRASER.

This contains many inaccuracies:

1) Not all vibrating viscometers are "rugged

" (POV) 2) Not all are "precise"...in fact, most are empirical devices in any but strictly Newtonian fluids. 3) Vibration amplitudes do not vary with the viscosity in all, or indeed in most vibrational viscometers. In the Nametre, Brookfield, and other vibrational viscometers the amplitude is held constant. 4) The sensitive part is not "very small" on all vibrational viscometers. Nor would this necessarily be an advantage, particularly in slurries or other suspensions with large particles. How small is "very" small? 5) I am familiar with the patent literature of vibrating viscometers, and most do NOT "follow the original design patented by SOFRASER".

Furthermore, in the interest of fairness, we should either include a representative sampling of advertising sites for ALL types of vibrational viscometers, or none.

The SOFRASER web site contains the following explanation of the instrument's principle:

The active part of this portable viscometer is a vibrating rod held in oscillation by a constant electrical power.

The vibration amplitude varies according to the product's viscosity where the rod is immersed.

The signal converter associated (7000 or 8000x family) allows the vibration and processes the amplitude variations in order to deliver a calibrate viscosity response.

This description adds nothing to the information already in the article, so the purpose of the link can only be commercial spam. Diogenes 05:03, 20 August 2007 (UTC)[reply]

The initial comment that most vibrational viscometers derive from the Bendix design is relevant and true. There really does need to be something more than is in the current section on vibrating element viscometers. There are two articles on Eng-Tips FAQs that might be considered more appropriate especially as they discriminate between "Behavioural"! and "Analytical" measurements. This difference is best illustrated by comparing the Halikeinen Process Capillary Viscosity Analyser

which is used to determine the viscosity at a reference temperature and the alternative Halikeinen design of a process capillary viscometer for behavioural measurements (fuel oil heater control) as later evolved into the VAF Viscochief. 

These are about as different as can be despite the basic principle of capillary flow being used. http://eng-tips.com/faqs.cfm?fid=1699 and http://eng-tips.com/faqs.cfm?fid=1004 — Preceding unsigned comment added by Plodding (talk • contribs) 20:55, 9 March 2011 (UTC)[reply]

The commercial links to Rheotec and Rheosys are spam. They offer no elucidation of basic principles. Compare, for instance, to the entries on "Mass Flow Meter" or "Magnetometer". The link on "Mass Flow Meter" points to an enlightening desription of the function of the device, not to advertising material. "Magnetometer" contains no commercial links. Diogenes 19:08, 20 August 2007 (UTC)[reply]

I've removed this spamming info. The SOFRASER company is spamming its product all over other wikis, see italian article too). Jalo 13:34, 13 November 2007 (UTC)[reply]

I am reading this portion of the article. I see some equations relating to force on and velocity of objects moving in viscous fluid. How does the device work? How do the equations relate to the operation of the device? The way this is written is not very helpful. — Preceding unsigned comment added by Skysong263 (talk • contribs) 03:36, 13 March 2011 (UTC)[reply]

ویسکومتر (همچنین می توان "ویسکوزیته متر"گفته می شود ) وسیله ای برای محاسبه ی ویسکوزیته سیال می باشد.برای سیالی که با تغییر جایگاه سیال تغییر می کند و دستگاه آن به به [rheometer] معروف است — Preceding unsigned comment added by Ldradoo (talk • contribs) 07:15, 19 April 2011 (UTC)[reply]

I want to propose a new section to this for Slit Viscometers. Before I do, I would like to submit the proposed text for peer review from this group. You can see the proposed text on my User Page. Please post comments to my Talk Page. Thanks. --AM Oatmeal (talk) 18:47, 24 January 2012 (UTC)[reply]

"speed and torque measurement" - I think there is no torque - directly - measured, but 1. the rotation speed of the outer tube und 2. the rotating speed of the inner rotor. By having calibrated the function torque by speed of the "magnetic brake" one can calculate backwards the braking torque. --Helium4 (talk) 15:15, 1 May 2014 (UTC)[reply]

In process measurement we have to be careful not to discriminate too freely in favour of rotational viscometers and too freely against vibrational or other technologies.

It is generally thought that vibrational sensors cannot be used with non-Newtonian fluids but this is not strictly true. Vibrating element viscometers can be used successfully for process control with non-Newtonian fluids. It is important to remember that what the process engineer requires to control a process is a repeatable measurement. It does not have to be a true viscosity measurement. A great many laboratory and process instruments are "empirical" devices and often with their own units of measurement. A good example is the Polymer Melt Index sensor used to control the polymerisation reaction in plastics manufacture. This is basically a capillary device but the fluid is far from Newtonian. Likewise the vibrational sensors are used in Methyl Methacrylate Polymerisation reaction control for end point spotting. In this application the polymerisation process initially requires heating to promote the reaction and then becomes exothermic. Temperature changes complicate what is an analytical measurement and one where the objective is to find the mean molecular weight. A typical reaction can take 2 hours and the end point can have a window of less than one minute. The conventional method of control was to take a sequence of samples and make a crude "cup" measurement and to plot the reaction progress and hence try to predict the time at which the reaction should be quenched. There are a lot of good practical reasons why mechanical viscometers are unsuitable but vibrational element sensors proved very successful not in predicting the end point but in detecting it. There are many such applications including those where the non-Newtonian behaviour is far less pronounced at the process conditions providing very good repeatable measurements under process conditions. In many such applications the control of the process requires a real time repeatable measurement but if samples are taken for laboratory measurement of the true viscosity this can be a time consuming operation. For example, in the oil industry a laboratory capillary viscometer to ASTM D445 can take an hour for each sample measurement, including the sample cycle time and the cleaning cycle. By the time the measurement is made the process has moved on. It is not unusual that such laboratory measurements become corrupted. In many applications the key to delivering a repeatable measurement is to control the process conditions such as to control the shear rates - for example, using constant flow rate. This point highlights a difficulty with rotational viscometers which in the lab deliver a well defined shear rate but in process, because of the need to have a flowing sample, there is the complication of the flow shear through the sensor as well as the shear imparted by the sensor so the same issue is faced by both types of sensor.

In refining online sensors are used for blending control where multiple streams maybe being blended to achieve a number of different target parameters. However, the quality is defined by the laboratory and frequent samples are taken for laboratory analysis during the process to provide verification of the process measurements. For viscosity the same principle can be applied of using properly conducted laboratory analysis to verify the repeatable values generated by a process viscometer even with a non-Newtonian fluid and a vibrating element sensor. It should be recalled that while the laboratory may be used to investigate the viscosity of a fluid, process control is most often about maintaining the viscosity at a set point value. This lends the process to the control of a range of different factors, not least the viscosity itself. All too often the lack of suitable process viscometers has lead to a dependence on laboratory measurements and consequently to a laboratory "mindset" about the measurement which is not always appropriate to a process measurement.

The process viscometer is not intended to deliver an accurate viscosity measurement so much as it is intended to provide a repeatable measurement used to maintain a consistent quality which is audited by laboratory measurements.

Sensor size: In measurement terms a smaller size sensor is generally associated with lower viscosity ranges but there are other factors in process measurement which must also be addressed. Smaller sizes bring pluses and minuses to the appropriateness of the sensor.

It would be interesting to see some inclusion in this article discussion of some of the newer technologies such as Acoustic wave (SAW) devices and ultrasonics. MeyerMeyer (talk) 15:55, 23 August 2014 (UTC)[reply]