2
INTRODUCTION
The A70 Rainfall Transmitter converts the signal from the
tipping bucket rain gage into an electrical signal for input
to a computer, meters or other instrumentation. It features
reliability, low cost, low power drain, accuracy, simplicity
of operation and ruggedness.
In ramp mode each tip of the bucket causes the output
signal to increase 1% of full scale.
Each complete excursion of the output signal from zero to
full scale represents 100 tips of the bucket. This corre-
sponds to one inch or 100 mm of rainfall depending on the
calibration of the rain gage. During periods of no rain
there is no change in the output signal.
In rain detector mode each tip of the bucket causes the
output to change to full scale for a user selectable time
period of 1 to 80 minutes. The timer in the rainfall
detector mode is retriggerable meaning that a new time
period starts with each tip of the bucket. If bucket tips
occur faster than the selected time period the output will
remain continuously at full scale.
Running average and other signal output formats are
available. Contact Comptus for additional information.
The Transmitter is protected from lightning damage with
metal oxide varistors.
Figure 1
Ramp Mode Output Signal
SPECIFICATIONS
Operating Power 12-24 Vdc
Input Device:
Tipping Bucket Rain Gage
Output:
Rainfall 4 to 20 mA
1 - 80 minute period pulse
Range:
/E - 1 inch, /M - 25 mm
Resolution:
/E 0.01 inch, /M 0.25 mm
Accuracy:
Electronics: +/- 1 %
Rain Gage: See Spec. for gage supplied
Temperature
Electronics - 0 to 70 Degrees C.
Range:
-40 to 70 Degrees C. available
Dimensions:
PWB: 6."l X 2.75"w X 1"h
Weight:
Transmitter Track Mount - 1 lb.
Maintenance:
Recalibrate system yearly
Connectors:
Terminal Strip to accept
AWG #12 to #22 Wire
Accessories:
A70-EO Power Supply
A70-LPD Loop Powered Display
A96 Lightning Arrestor
Figure 2
Rain Detector Mode Output Signal
4
Current
12
8
mA
20
16
Loop
Bucket Tips
Time in Minutes
20 40 60 80 100
120 140
0
20 min.
20 min.
20 min.
8
4
16
12
20
Current
Loop
mA
Total Rainfall
Inches
1