TB4, TB4MM, CS700, and CS700H Tipping Bucket Rain Gages
14
8.2 Long Cable Lengths
Long cables have appreciable capacitance between the lines. A built up charge
could cause arcing when the switch closes, shortening switch life. A 100 ohm
resistor is connected in series at the switch to prevent arcing by limiting the
current (FIGURE
). This resistor is installed on all rain gages currently sold
by Campbell Scientific.
8.3 CS700H Heated Rain Gage Operation
This section provides a brief discussion of the CS700H heater
operation. More in-depth information is provided in Appendix
(p. C-1)
.
The CS700H includes heating elements and an internal snow sensor, which is
activated when the air temperature drops below 4 °C. If the snow sensor detects
snow in the catch area (funnel), the heating elements automatically turn on and
keep the funnel temperature at 10 °C. The heater goes into a wait mode when
snow has not been detected for 18 minutes. It automatically deactivates when
the air temperature drops below –20 °C.
As the ambient temperature falls below the
Active On Temperature
(default
4 °C), the heater will turn on to heat the funnel area of the rain gage. Once the
funnel reaches the
Funnel Set Point Temp
(default 10 °C), the heater will begin
cycling on and off with a duty cycle dependent on the ambient temperature,
keeping the funnel temperature at or near 10 °C (FIGURE
).
FIGURE 8-2. CS700H Heater Operation
8.3.1 SDI-12 Measurements
The
M!
,
C!
, and
R!
SDI-12 commands retrieve the following status
information from the CS700H:
1.
Ambient temperature (°C or °F)
2.
Block temperature (°C or °F)
3.
Units (0=°C, 1=°F)
4.
0=no snow; 1=snow detected
NOTE
