264 



HYDRAULIC EQUIPMENT 



Connections to the registering instrument are made by two 

 small pipes, one at the inlet pressure chamber and the other at the 

 throat pressure chamber. No water flows through these pipes as 

 they simply transmit the two pressures, the difference in which 

 controls the readings of the instrument. 



Registers. There are different kinds of registers, the most 

 complete being illustrated by Fig. 144. At the back there are 



two vertical wells connected at the bot- 

 tom. One well is subjected to the 

 inlet and the other to the throat 

 pressure of the Venturi Meter Tube, 

 these pressures being transmitted by 

 the two small pipes as previously 

 mentioned. In one well is a heavy 

 metal float resting upon the mercury, 

 a part of which flows from this well 

 to the other well in direct proportion 

 to the changes in flow through the 

 Venturi Meter Tube. This is accom- 

 plished by having the receiving well 

 of a variable cross-section. Conse- 

 quently, the large float descends in 

 direct proportion to the change in rate 

 of flow and its motion is transferred 

 to the main shaft of the instrument 

 by means of a rigid float rod and suit- 

 able gearing. The movement of the 

 shaft is in turn transferred by means 

 of rack-and-spur gearing to the long 

 main lever of the instrument which 

 carries the chart pen and the integrat- 

 ing counter. 



The recorder dial contains a large 

 circular chart giving an unbroken 

 autographic record of the rate of flow through the meter tube. 



The counter dial shows the total amount of water (gallons, 

 cubic feet, etc.) which has passed through the tube. 



The indicator shows the exact rate of flow in gallons per day 

 or other units at the moment of observation. 



Where the expense of installing a complete registering outfit 



FIG. 144. Venturi Meter 

 Register. 



