Brookfield Falling Ball KF40 Bedienungsanleitung PDF herunterladen (Seite 18)

Brookeld Engineering Labs., Inc. Page 18 Manual No. M11-353-A0512

Appendix B - Calibration of the Ball Constants

Brookeld’s certication of the instrument is performed with Ball #2 and Ball #3 as well as

using the Cannon N44 viscosity standard with a nominal value of 92mPa

•s at 20°C.

Re-calibration of the ball constants is required by the operator if:

1. changes in the sample tube or water jacket were made

2. one or more balls were replaced

The calibration requires the use of a Newtonian mineral oil viscosity standard. Choice of the

viscosity standard is according to the ball. Use the appropriate Cannon or Brookeld viscosity

standard that falls within the viscosity measurement range.

BALL NO. 1 2 3 4 5 6

Recommended Viscosity

Standards

(cP, mPa•s)

Cannon Cannon Cannon Cannon Cannon N/A

S3 N10 N100 N350 N1000 N/A

3.9 cP @

20°C

21 cP @

20°C

283 cP @

20°C

830 cP @

20°C

2900 cP @

20°C

N/A

The calibration is made according to the method in DIN 53015 at 20°C ± .05 C. A suitably

calibrated thermometer can be obtained from your Brookeld dealer, on request.

Ball #6 is not recommended for use in performing a calibration check.

The ball constants are determined from (5) running times, in both forward and reverse direction.

The ball constant is calculated according to the following equation:

Equation 3:

K =

(ρ

-ρ

)

• t

t Mean value from 5 running times [s]

η Dynamic viscosity of the calibrating uid [mPa•s] at 20°C ± .05 C

Density of ball [g/cm

]

Density of calibrating uid [g/cm

]

Note: Be sure to measure the sample density at the same temperature at which the viscosity

will be measured.

The expected value of the constant should be similar to the constant stated in the test certicate.

For Ball No. 6, the ball constant changes insignicantly as a function of the falling tube diameter

and diameter of the ball, so that the ball constant is calculated according to the following equation:

Equation 4:

= 1.4057(D-d

)

(0.75042+1.82637 )

D Falling tube diameter (see calibration certicate)

Diameter of Ball No. 6 (see calibration certicate)

Ball constant of Ball No. 6

1 2 ... 13 14 15 16 17 18 19

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