Model 35 Viscometer

The Fann Model 35 Viscometer is widely known as the “Standard of the Industry” for drilling fluid viscosity measurements. The Model 35 Viscometer is a versatile instrument for research or production use.

In the six-speed models, test speeds of 600, 300, 200, 100, 6 and 3 rpm are available via synchronous motor driving through precision gearing. Any test speed can be selected without stopping rotation. The shear stress is displayed continuously on the calibrated scale, so that time-dependent viscosity characteristics can be observed as a function of time. The Model 35A Viscometer is powered by a 60-Hz motor; Model 35SA Viscometer by a 50-Hz motor.

The twelve speed models allow measurement over an extended shear-rate range.Test speeds of 600, 300, 200, 180, 100, 90, 60, 30, 6, 3, 1.8 and 0.9 rpm are available via a synchronous motor driving through an SR12 gear box and then through the precision gearing, as defined for Model 35 Viscometer.The additional 10:3 speed reduction is selectable through a two-position gear-shift lever. The SR12 gear box can be retrofitted to Model 35 Viscometers.

These instruments are equipped with factory installed R1 Rotor Sleeve, B1 Bob, F1 Torsion Spring, and a stainless steel sample cup for testing specified by the American Petroleum Institute. Other rotor-bob combinations and/or torsion springs can be substituted to extend the torque measuring range or to increase the sensitivity of the torque measurement.

Shear stress is read directly from a calibrated scale. Plastic viscosity and yield point of a fluid can be determined easily by making two simple subtractions from the observed data when the instrument is used with the R1-B1 combination and the standard F1 torsion spring.

The FANN Model 35 Viscometer has been evaluated and are compliant with the following standards:

EN 61010-1:2010
UL 61010-1:2010
CSA C22.2 No. 61010-1-12

For further details, refer to the Declaration of Conformity.


Six speed viscometers have speeds of 600, 300, 200, 100, 6, and 3 rpm. Twelve speed viscometers have speeds of 600, 300, 200, 180, 100, 90, 60, 30, 6, 3, 1.8, & 0.9 rpm.

Part No.Model NumberNumber of SpeedsVoltage
20719835A6115 Volts 60 HZ
20719935SA6115 Volts 50 HZ*
20720035A/SR-1212115 Volts 60 HZ
20720135SA/SR-1212115 Volts 50 HZ*
10167176735SA/SR-12 with Case & Transformer12115 Volts 50HZ
10167176835A with Case6115 Volts 60 HZ
10167177035SA with Case & Transformer6115 Volts 50 HZ
10167177135A/SR-12 with Case12115 Volts 60 HZ
*Requires Step Down Transformer (Part No. 205722) to operate on 230 Volts.

Weights & Dimensions (All Models)

Dimensions: 15.2" x 6" x 10.5"
Weight: 15 lbs