Firma:              Brookfield

Modell:            LVT

Kommentar:    Dokumente engl.

Principle of Operation

The Brookfield Digital Viscometer rotates a sensing element in a fluid and measures the torque necessary to overcome the viscous resistance to the induced movement. This is accomplished by driving the immersed element, which is called a spindle, through a beryllium copper spring. The degree to which the spring is wound, detected by a rotational transducer, is proportional to the viscosity of the fluid.

Continuous readout of viscosity can be accomplished in two ways: by means of the integral three-digit LED display, or by the 0-10 mv analog output signal which can be fed into a variety of indicating or recording devices.

The Viscometer is able to measure over a number of ranges since, for a given spring deflection, the actual viscosity is proportional to the spindle speed and is related to the spindle's size and shape. For a material of given viscosity, the drag will be greater as the spindle size and/or rotational speed increase. The minimum viscosity. range is obtained by using the langest spindle at the highest speed; the maximum range by using the smallest spindle at the slowest speed.

Measurements mode using the saure spindle at different speeds are used to detect and evaluate the rheological properties of the test material. Our booklet, "Solutions to Sticky Problems" discusses the Viscometer's use in this respect.

Introduction

The Digital Viscometer is powered by a precision synchronous motor. Exact speeds of rotation are assured as the motor will turn erratically and spasmodically if synchronism cannot be maintained.

Speed changes are effected by a transmission having eight speeds. The square speed control knob has two numbers on each face; by moving the knob through two complete turns the eight speeds may be selected in sequence. No trouble will be experienced in differentiating between the two speeds shown on each face, since each pair is in the ratio of 20:1.

To ensure rotation at the indicated speed it is important that the face of the knob upon which this speed is shown be closely parallel to the Viscometer's base. Although not absolutely necessary, it is advisable to change speeds while the motor is running.

LV Viscometers are provided with a set of four spindles and a narrow guard leg; RV Viscometers come with a set of seven spindles and a wider guard leg; HA and HB Viscometers come with a set of seven spindles and no guard leg.

The spindles are attached to the Viscometer by screwing them to the Iower shaft. Note that the spindles have a left-hand thread. The Iower shaft should be held in one hand and the spindle screwed to the left. The face of the spindle nut and the matching surface on the Iower shaft should be smooth and clean to prevent eccentric rotation of the spindle.