Xylem H-340-CalKit - Manual (Page 3)

Introduction
H-340-CalKit
Instruction Manual 1-1
1.0 Introduction
The H-340-CalKit includes the apparatus to verify and adjust the calibration of a H-340 Tipping
Bucket Rain Gauge.
Tipping bucket rain gauges have a reputation for being inaccurate. Inaccuracies can be caused by
algae in the bucket, evaporation and poor calibration. The greatest source of inaccuracy however,
is the volume at which the tipping bucket mechanism tips is sensitive to rainfall rate. This occurs
because the water droplets cause small waves in the bucket and high rainfall rates cause
superposition or “pile up” of extra water in the bucket before it actually tips over. Design Analysis
Associates makes two different rain gauge models. The model H-340 is a standard tipping bucket
rain gauge with a switch closure output. The model H340-SDI has a SDI-12 output and an
internal microprocessor which compensates for the flow rate sensitivity by measuring the time
between bucket tips.
The H-340-CalKit is used to field calibrate a standard H-340 rain gauge. The H-340-SDI
requires a more complex apparatus which delivers a constant flow rate and the calibration must be
performed at the factory.
The H-340-CalKit provides for a calibration of
one tip per 0.01 inches of rainfall at a mean
rate of 4.00 inches of rainfall per hour, the rate
starts at a rate greater than 4.0 in/hr and
diminishes as the bottle drains.
The H-340-CalKit includes:
1 ea Water bottle with valve attached
1 ea Water bottle mount with
built-in orifice
2 ea 250ml graduated cylinders
2 ea 24-inch plastic drain hoses
1 ea Orifice brush