(n). Drilling Fluids. Also known as direct-indicating viscometer or V-G meter, an instrument used to measure viscosity and gel strength of?drilling mud. The direct-indicating viscometer is a rotational cylinder and bob instrument. Two speeds of rotation, 300 and 600 rpm, are available in all instruments, but some are 6- or variable-speed. It is called "direct-indicating" because at a given speed, the dial reading is a true centipoise viscosity. For example, at 300 rpm, the dial reading (511 sec-1) is a true viscosity. Bingham plastic rheological parameters are easily calculated from direct-indicating viscometer readings: PV (in units of cp) = 600 dial - 300 dial and "YP" (in units of lb/100 ft2) = 300 dial - PV. Gel strength is also directly read as dial readings in oilfield units of lb/100 ft2. Syn: direct-indicating viscometer, V-G meter See: Bingham plastic model, deflocculant, gel strength, Herschel-Bulkley fluid, Newtonian fluid, non-Newtonian fluid, plastic viscosity, power-law fluid, rheological property, yield point