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**Sensor:** All Weather Precipitation Gauge

**Manuf/Model:** GEONOR, T-200B

**Description:**

The GEONOR precipitation gauge is a weighing type gauge. The T-200B uses
vibrating wire strain gauges to continuously weigh the collection
bucket. The 12-liter collection bucket is suspended by [three vibrating
wire sensors]{.underline}.

**How is it installed?**

The gauge is mounted via a Holleander pedestal mount to a 6-foot long 2"
aluminum pipe. This pipe is mounted 3.5 feet deep in 2' x 2' x 3'deep
poured concrete block. The poured concrete is extended to 2 feet above
the surface at a diameter of 1.25 feet. The gauge is bolted to the
pedestal and all sensors, surge suppressors, and weighing bucket mounts
are attached. The sensors and suppressors are connected electrically to
their appropriate positions. The bucket is added to the bucket mount and
the bucket is leveled via the adjustment nuts on the strain gauges. The
sensors are then calibrated using the 'GEONOR Rain gauge Calibration
Procedure'. The gauge is surrounded by a Small DFIR and Single Alter
wind/snow shield. A controlled heater device is attached to the gauge.

**Why measure this parameter?**

Precipitation amounts (accumulations) are a primary measurement for the
USCRN Program.

**How are data recorded?**

The vibrating wire, when excited with 12V DC, outputs a frequency (Hz)
relative to the weight in the collection bucket. The actual frequency
measured for the sensor is averaged each hour and the hourly frequency
maximum and minimum is calculated. These calculations are done for each
of the three sensors and reported independently.

**How are data computed?**

[For each of the three vibrating wires]{.underline}, the frequency is
measured every two seconds using the CR23X period average command with
the frequency output option (P27). A running average of the last 30
samples of the frequency is calculated using a CR23X P52 running average
command. This is done to decrease false reports of precipitation caused
by wind noise. The frequency is converted into a measure of the
precipitation level in the bucket using the formula P=
A(f-f0)+B(f-f0)\*\*2, where P is the precipitation level in the bucket
in cm, A and B or sensor constants determined by calibrations and
entered into the program, f0 is the sensor frequency with the bucket
empty, and f is the measured frequency average of the last 30 samples.
The result is converted to mm by multiplying by 10.

The Geonor measures the precipitation level in the bucket, thus the
amount of precipitation that occurred in the last 15 minutes is
calculated at the end of each 15 minute period. Small fluctuations occur
in the measured precipitation level in the bucket due to temperature
changes and sensor variations, thus a minimum change of .25 mm (.01
inch) is required to cause precipitation to be reported. The CR23X
calculates a term referred to as the "last level". The last level is
initialized to the current precipitation level when the CR23X is first
programmed. At the end of each 15 minute period the calculated
precipitation level is compared to the last level. If the precipitation
level is greater than the last level by more than .25 mm, the difference
is reported as precipitation and the last level is reset to the current
precipitation level. If the precipitation level has decreased by more
than .25 mm the last level is reset to the current precipitation level.
This could be due to evaporation or emptying of the bucket by the site
operator. Any decrease in the precipitation level is reported as zero
precipitation.

At the end of each 15 minute period the 15 minute calculated
precipitation amount is stored according to the quarter hour past. The
last calculated precipitation depth is recorded. At the end of each hour
the four 15 minute precipitation amounts are totaled.

**What data/information are stored in the data logger?**

Each 15 minute calculated precipitation amount according to the quarter
hour past, the last calculated precipitation depth, the hourly total
from the four 15 minute precipitation amounts, and the associated hourly
average, maximum, and minimum frequency values [for each of the three
vibrating wires]{.underline} are stored in the data logger.

**What values are transmitted?**

[For each of the three vibrating wires:]{.underline}

\- The hourly average, maximum, and minimum frequencies.

\- The calculated precipitation for 0-15, 15-30, 30-45, and 45-60
minutes, and the Hourly Total.

\- The calculated precipitation level at the end of each 15 minute
period.