JOWL OF AGWCULT1AL RESEARCH 
DEPARTMENT OF AGRICULTURE 
Voi,. II Washington, D. C., May 25, 1914 No. 2 
BEHAVIOR OF CUP CURRENT METERS UNDER CON¬ 
DITIONS NOT COVERED BY STANDARD RATINGS 
By Fred C. Scobey, 
Irrigation Engineer , Office of Experiment Stations 
Experience gained in taking a long series of canal measurements led 
the writer to believe that the conditions met in field measurements 
of the flow of water in open channels by the use of current meters varied 
so widely from those under which the meters are rated as to render 
inaccurate to an appreciable degree the results of field measurements 
computed on the basis of the ratings usually made. For the purpose of 
determining this point, a series of experiments was made, with the results 
reported here. 
The meter used was the small Price meter commonly used for deter¬ 
mining the velocity of flowing water. The usual practice in rating a 
current meter is to make the tests for all velocities with the meter at the 
same distance beneath the surface of the water—from 1 to 2 feet—and 
far enough from the sides and bottom of the channel or reservoir in which 
the rating is made and from all obstructions to be beyond their influence. 
In addition, the meter is usually held quite rigidly in a horizontal position, 
on either a rod or a cable. In field use, on the contrary, the meter is 
used from the surface to the bottom and close to the sides of the channels 
throughout the entire range of depths found in the streams measured; 
and in high velocities there is a strong tendency for the meter to be forced 
out of its horizontal position. The tests discussed here were made for 
the purpose of determining whether the standard ratings, made as de¬ 
scribed, hold good when the meter is held near the surface of the water 
or near the sides or bottom of the channel or out of the horizontal. 
Further tests were made to determine the effect of the movement of the 
meter in the water when the “integration” method is used and also 
the effect of dulling the pivot bearing of the meter. 
On September 5 and 6, 1913, a series of runs was made at the meter 
rating station of the California Development Co., at Calexico, Cal. 1 
1 For a detailed description of this station, see Allison, J. C., Selling water by current meter measure* 
ment, in Engin. News, v. 69, no. a, 1913. 
Journal of Agricultural Research, Vol. II, No. a 
Dept, of Agriculture, Washington, D. C. May a s, 1914 
B-i 
41217”—14-1 
(77) 
