Can I compare measurements between two different viscometers?

You must discuss with a colleague, a customer, a supplier about viscosity measurements and you are not sure to speak the same language, you will find below some explanations which should allow you to better understand yourself.

First of all, there are 2 categories of products:

• Newtonian fluids: These are perfect fluids whose viscosity does not depend on agitation (water, standard oils, etc.)
• Non-Newtonian fluids: These are fluids whose viscosity depends on agitation, and it is the vast majority of products that we meet (paints, gels, creams, food products ...)

In the case of a Newtonian product:

At a given temperature, whatever the measurement method and the device used, you will always have the same result and the measurements will be comparable between two devices.

For non-Newtonian products:

These products have a viscosity which depends on the stirring, so if we change the type of viscometer, mobile and / or speed then we will not measure the product under the same stirring conditions and therefore you will not be able to compare. the results.

When you want to compare the results between two Brookfield viscometers, you must ensure that the following 7 parameters are identical:

In the case of relative viscosity measurement (standard mobiles supplied with the device or Helipath mobiles)

• Device type (LV, RV, HA or HB)
• Mobile
• Speed
• Sample temperature
• Measurement time (the viscosity of the products often depends on the stirring time and therefore measurement)
• Beaker used & presence of the caliper (normally you should use the low size 600 ml beaker and the caliper, if this is not possible, specify that you did not put the caliper and used such a beaker reference)
• Product history (a product which has just been stirred will not necessarily have the same viscosity as a product which has been at rest for several minutes or hours ...)

In the case of the use of measurement geometries (cone / plane, coaxial cylinders as with the SSA, ULA or thermosel accessory or finally the spiral adapter) allowing absolute viscosity measurements (at shear rate expressed in s -1), it should be specified:

• Shear rate (in s-1)
• Sample temperature
• Measurement time
• Product history

Can I compare results between an LVDV2T viscometer and an LVDVnext rheometer?

Can I compare results between LDV2T and an RVDV2T rheometer?

The references of Brookfield viscometers and rheometers are composed

• a prefix indicating the type of sensor used (LV, RV, HA, HB)
• followed by a suffix indicating the type of measurement box (analog, DVE, DV1M, DV2T, DVNext)

It is possible to compare results between two viscometers equipped with the same sensor (and the results will be strictly equal). LVDV2T and LVDVNext in the example

It is not possible to compare results between two viscometers equipped with different sensors (except for Newtonian products): LVDV2T and RVDV2T in the example

Can I compare results between a Brookfield viscometer and a competing rheometer?

You must compare the results between your Brookfield viscometer and a competing rheometer not equipped with Brookfield type mobiles. How to do?

As specified above, Brookfield viscometers are delivered equipped with standard mobile LV 1 to LV4 or RV2 to RV7 (mobile RV1 optional)

These mobiles make it possible to make relative viscosity, that is to say that the results will depend on the mobile-speed combination chosen (for non-Newtonian products)

The competing rheometer not equipped with standard Brookfield mobiles will therefore measure the product under stirring conditions which will not be identical to those used with standard mobiles. He measured the product at a defined shear rate (expressed in s-1)

Also, all you have to do is install a Small Sample Adapter (SSA), Ultra Low Adapter (ULA), Thermosel or Spiral adapter on your Brookfield viscometer to be able to measure the product at a defined shear rate.

It is then necessary to adjust to exactly the same shear rate (in s-1) between the Brookfield viscometer and the competitor's rheometer to obtain the same results.

Take care to check that at this shear rate the measurement range of your device is compatible ...

Can I install RV mobiles on my LVDV1M viscometer?

I have an LVDV1M viscometer and my client tells me that in his method he works at 25 ° C, measures for 1 minute with the RV3 mobile at a speed of 10 rpm.

Can I buy the RV3 rover to take measurements on my LVDV1M?

Even if it is technically possible to install an RV3 rover on an LVDV1M viscometer, this will not solve the problem ...

In fact, the full scale (maximum measurable viscosity) is calculated as follows:

FSR = TK * SMC * 10,000 / RPM

TK = Spring constant (for an RV: TK = 1, for an LV: TK = 0.09373)

SMC = Mobile constant (The constants of each mobile are specified in the appendices of all the user manuals)

RPM = Rotation speed (in revolutions per minute)

The measurement range is between 10% and 100% of full scale FSR, measurement accuracy: 1% of full scale.

So if we work on an LV viscometer or an RV viscometer, with the same RV3 mobile and at the same speed of 10 revolutions per minute, we will create an identical agitation even the measurement ranges will no longer be the same (about 1 ratio of 1 to 10 between LV and RV) ...

In the example:

RV3 speed 10 RPM installed on an RV viscometer: the measurement range is between 1000 and 10,000 cp with an accuracy of + - 100 cp

RV3 speed 10 RPM installed on an LV viscometer: the measurement range is between 93.7 and 937 cp with an accuracy of + - 9.37 cp

This proves that it is not wise to use LV mobiles on an RV viscometer (or vice versa)

Generally speaking, the rule is simple: we use

• LV mobiles on LV viscometers,
• RV mobiles on RV viscometers.