intervals ranging from 1- to 60 seconds around the
4
5
clock. Their system had a maximum range of 11.46
m (37.6 ft). This system has an additional advan-
tage in that, with the proper siting, it could also
2
double for measuring ice thickness (see following
section on Ice Thickness). The greatest drawback
to the use of either ultrasonic or radar systems is
1
that they measure to the first surface encountered.
In other words, when a stream is ice covered, the
distance to ice would be measured, rather than the
+
distance to true water surface. If true stage were
3
desired by use of either system, it would be nec-
essary to keep an area of open water below the
instrument.
Figure 10. Section view of ultrasonic stage recorder: 1
The system described by Yankielun and Ferrick
is the ultrasonic sensor, 2 is the data logger, 3 is the
consisted of the radar front end, a function gen-
power source, 4 is the weatherproof enclosure, and 5 is
erator, a dynamic signal analyzer, and a 12-bit
the output port for downloading data to a laptop or tele-
analog-to-digital converter internal to a laptop
phone.
computer. The radar front end consists of a volt-