I was thinking a bit more, and a simple solution may be a drag-line idea, measuring the strain being pulled on the line.
This keeps the sensor out of the liquid, and possibly the fumes, and simply has a non volatile (stainless?) wire to the immersed object.
The problem is those two acids attack almost everything !
Thanks for your idea. But unfornately my process will affect the stainless.
What is the material that contains, keeps, those aggressive fluids? Use that material.
Is nylonline, or carbon fibre thread useable ?
Glass is one of the most chemical resistant materials out there, the only chemical that I know of to attack glass is HF (hydrogen fluoride).
For low shear stresses it should do quite well as a spindle, it is of course very brittle.
wvmarle:
Many years ago I've been working with various kinds of viscosity meters. Those no doubt were bought commercially by the university. No doubt nowadays they have different communication options for a computer (or Arduino, if you prefer) to read the viscosity reading from the viscometer. Those were based on a cylinder rotating in the liquid, then calculating the viscosity based on the torque.That's the way to go if all you want to achieve with this project is a reading of the viscosity of your material. The test cylinder will have to be made of a highly chemical resistant material for use with your acids, of course. Ask the manufacturer for suggestions.
Now if you're interested in the ins and outs of measuring viscosity, you may go the complete DIY route and start with a spindle, motor, torque sensor, etc. Based on your messages I don't have the feeling that this is what you're after.
Hi,
Now, I have Spindle (40mm dia and 100mm Height)which is chemically resisted, DC motor... Now I am in the search of Torque sensor. basic doubt I want to measure kinematic viscosity. There is no external force applied except gravity. I hope in this rotational method we can get dynamic viscotiy. Can use the formula Kinematic viscosity = Dynamic / Density. Is it Ok?
Dear All,
I made some diagrams to build the viscometer. I hope, with this arragement I can measure the viscosity and record too.
Please share your opinion/ suggestions about this idea.
I am looking for open comments....
No idea if this can work or not... try it!
@Wvmarle What about the concept ?
I can't really figure out your intended measurement method from that image. It seems your intention is to measure the speed of flow of a certain amount of liquid through a tube?
Different methods tend to give different results, you will have to study your particular liquid to know how it reacts to different strain profiles. I expect your acids, as it is mostly ionic, to react fairly linear to strain. You will have to measure this, of course, if you can't find it in literature studies. If the linear flow rate of your liquid changes during the experiment, the strain changes, and with it the viscosity may change.
First thing to test is the level sensors. The ones in the image have a reaction time of about half a second, fast enough for me, maybe not for you. But you have to try whether they work with a thin glass tube. There may not be enough material in front of them to detect it.
The pumps use silicone tubing. I wouldn't be surprised if your liquid will have that for lunch, if not breakfast.
But again, by all means, start building and testing. I hope you do have a lot of time (a year or so) before you need actual results. The moment you get the liquid level sensors work, and you have the correct (sufficiently resistant) materials for your setup, you should quite easily be getting qualitative results on viscosity changes but I suspect you want quantitative results - so how do you intend to calibrate your setup?
Hi,
Thanks a lot for your detailed feedback. Let us see... I hope I will get a sensor by the day after tomorrow. I will check and update you.
wvmarle:
I can't really figure out your intended measurement method from that image. It seems your intention is to measure the speed of flow of a certain amount of liquid through a tube?
Yes - it's a "u-tube viscometer" and that's how they work. Another example: 
In one arm of the U is a vertical section of precise narrow bore (the capillary). Above there is a bulb, with it is another bulb lower down on the other arm. In use, liquid is drawn into the upper bulb by suction, then allowed to flow down through the capillary into the lower bulb. Two marks (one above and one below the upper bulb) indicate a known volume.
The time taken for the level of the liquid to pass between these marks is proportional to the kinematic viscosity. The calibration can be done using a fluid of known properties. Most commercial units are provided with a conversion factor.
Indeed, the response time (and precision) of the level sensors are likely to be key to the success of this setup.
I have several years of experience working with viscometers. I've been working on my own design which is how I ended up here. I grazed through the forum and saw the designs people were talking about. I've seen the rotary design being kicked around and it's the style I'd go with. You can get lots of info from fann. I'll post a link to the fann 35. You can get calculations and dimensions. To measure I'd measure the rpms, torque and volts and amps running through the motor turning the bob or rotor. The 25k machines have an encoder and they are measuring how much resistance the fluid is putting up. They make Arduino load cells I think they would be a good option to add if you can convert the force linearly. Get as many sensors as you can on there including temp and get calibration fluids. Water is 1 and they make calibration oils you can use too. I think it's very possible to make a usable viscometer using an Arduino, at least Newtonian fluids, Especially to find apparent viscosity. It may be difficult to measure nonNewtonian fluids. Look like the fann 35, Chandler 5550, the fann 50. Also Anton part has a bunch of educational material.
https://www.fann.com/fann/products/oil-well-cement-testing/viscosity/visc-model35.html
