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www.bindicator.com
LBY180112 Rev. B
III. PRODUCT DESCRIPTION
FUNCTION
The Bindicator®Yo-Yo™is a sensor that is mounted to the top of a vessel and measures the distance to the
product in the tank. This is done by lowering a weight to the surface of the product, while measuring the amount
of cable used. When the weight contacts the material, the unit senses the loss of weight. The motor reverses
and automatically returns the weight to its home position, sealing the weight against a bellows assembly in the
bottom of the sensor housing. The cable is measured while traveling in both directions and the readings are
compared. If these measured distances do not agree, the sensor automatically takes another measurement
reading. A microprocessor located on board has the ability to convert this measured distance to “level of
product” or “volume/weight of product” in the vessel. This value is communicated via RS-485 MODBUS to the
remote display or ORBTM. The signal may also be transmitted via 4-20 mA to other equipment.
APPLICATIONS
Bindicator Yo-Yo sensors provide level measurement in most dry bulk solid materials, liquid/solid interfaces, and
liquids at atmospheric pressure. These sensors can be used for measurement of materials with temperatures of up
to 200° F (93° C). Please consult the Bindicator Applications Department if this device will be used in material with
temperatures above 200° F (93° C).
Locatingthepropermountinglocationonthetopofthetankisimportant.Whenllingbulkmaterialsintoavessel,
a positive angle of repose (mound up) is created. When emptying, the angle of repose may become negative. In a
round,centerll-and-dischargevessel,thepointthatbestaveragesthisangleofreposeislocatedat1/6the diameter
of the tank (or 1/3the radius) from the outside wall.
The Yo-Yo sensor, like any other plumb bob device, drops a weight into the vessel. If the material in the vessel buries
this weight, the sensor will become inoperative. Therefore, it is not recommended that readings be taken when there
isachancetheweightwillbeburied.Thiscouldoccurwhenthevesselisbeinglledordischarged.
If material is sticky and will eventually build up on the weight, this will cause the weight to become stuck at its home
position inside the standpipe. In order to avoid this, a tare stop is available. The tare stop will still seal against the
bellows when in the “home” position, but the weight is left suspended below the standpipe. If build-up does occur on
the weight, it will not become stuck because it never enters the standpipe.
Considerationshouldbegiventoairowcharacteristicsinthevesselwhenthereisnoproductmovement.The
internal dynamics of bulk solids storage vessels can vary drastically. If your vessel includes air movement equipment
thatcontinuouslyltersormovesair,thiscouldcauseproblemswiththeweightwhenitisdroppedintothevessel.Air
currents can cause the weight to swing or spin as it is being lowered or raised inside the vessel. If the weight spins,
it can create knots in the cable. Knots in the cable could hinder the movement of the weight as it is being retracted,
or on the next measurement when it is lowered. A swinging weight can be the cause of inaccurate readings or can
abrade and eventually cut the cable as a result of rubbing on the edge of the standpipe at the top of the vessel.
