Brookfield KU-1 Viscometer - Manual (Page 9)

Brookfield Engineering Labs., Inc. Page 9 Manual No. M/97-241-B1101
6) After you have recorded results in KU, then move the Selector knob to the "gm" position and
record your reading in grams. If you are using a printer, both measurements will be sent to
the printer and will print out as soon as the Hold Display switch is switched back to the
DOWN position.
Interpretation of Calibration Check Results
When verifying the calibration of the KU-1+, the instrument tolerance and viscosity standard fluid
tolerance must be combined to calculate the total allowable error.
The KU-1+ is accurate to
±
11 grams, which is 1% of the full scale range in grams. The Brookfield
Viscosity Standard is accurate to
±
1% of the stated viscosity in KU.
The total allowable error should be stated in KU. Since the instrument accuracy is stated in grams,
you will have to use the comparison table (Table A2) and convert from grams to KU.
Correct interpretation of your calibration results requires that you compare your readings in grams to
the equivalent in KU. You must then bracket your reading with upper and lower limits based on the
allowable error of
±
11.0 grams. Convert this acceptable range in grams (as defined by the upper
and lower limits) to KU units.
Example: Calculate the allowable error of the KU-1+ using fluid KU106; the stated
viscosity of the fluid is 104.8 KU. The viscometer indicated a measured viscosity
of 105 KU and 410 grams.
1) Measured results from the calibration check in grams were 410 grams. Locate 410 grams on
the conversion chart (Table A2).
2) The KU-1+ is accurate to
±
11.0 grams. Starting from 410 grams, count 11 places above and
below the 410 grams. This is called "bracketing" the acceptable range. In this case, the
acceptable range will be from 399 grams to 421 grams.
3) Convert the acceptable range in grams to KU. Locate the minimum and maximum grams
bracketed. Look to the right of each number for the conversion to KU. In this case, it will be
103.9 KU minimum and 105.7 KU maximum. The total difference between 103.9 and 105.7
KU is 1.8 KU. Therefore, the accuracy is
±
0.9 KU. This is the accuracy for the
Viscometer in KU,
±
0.9 KU.
4) Now that you have the accuracy for the instrument, you can add it to the accuracy of the
fluid. The fluid is accurate to
±
1% of the stated value in KU. The viscosity standard is
calibrated at 104.8 KU,
±
1% is equal to
±
1.0 KU.
0.9 KU (instrument accuracy)
+ 1.0 KU (fluid accuracy)
1.9 KU (total allowable error)