User guide

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appending the status byte <ss> which will, amongst other things, inform the calling program as to
whether the motor was turned on and/or whether the desired speed was attained. The Z(ero) command
is used to “zero” the DV-III Rheometer. The value returned <vvvv> is usually in the range of 03F0 hex
to 0400 hex. This number should be retained and subtracted from every future returned torque reading
to obtain the actual Rheometer torque in percent.
DV-III Viscometer Data Calculations
The following formulas should be used to calculate and display the Rheometer data after
each packet
of data is obtained from the DV-III.
Viscosity (cP) = 100
*
TK
*
SMC
*
Torque
RPM
Shear Rate (
1
/
Sec
) = RPM
*
SRC
Shear Stress (
Dynes
/
Cm
2
) = TK
*
SMC
*
SRC
*
Torque
Where:
RPM = Current Rheometer spindle speed in RPM
TK = Model spring constant from Appendix, D Table D2.
SMC = Current spindle multiplier constant from Appendix D, Table D1.
SRC = Current spindle shear rate constant from Appendix D, Table D1.
Torque = Current Rheometer torque in percent expressed as a number between 0 and 100.
As an example, consider an LV Rheometer using an SC4-31 spindle, running at 30 RPM and currently
returning a Torque of 62.3 percent. First we list all of the given data and include model and spindle
constant from Appendix D, Tables D1 and D2:
RPM = 30 from the example statement.
TK = 0.09373 from Appendix D for an LV Rheometer.
SMC = 32.0 from Appendix D for a type SC4-31 spindle.
SRC = 0.34 from Appendix D for a type SC4-31 spindle.
Torque = 62.3 from the example statement.
Applying this data to the above equations yields:
Viscosity (cP) = 100
*
TK
*
SMC
*
Torque
RPM
= 100 * 0.09373 * 32.0 * 62.3
30
= 622.9 cP
Shear Rate (
1
/
Sec
) = RPM
*
SRC
= 30 * 0.34
= 10.2
1
/
Sec
Shear Stress (
Dynes
/
Cm
2
) = TK
*
SMC
*
SRC
*
Torque
= 0.09373 * 32.0 * 0.34 * 62.3
= 63.5
Dynes
/
Cm
2