8
OPERATION
Continued
Voltage Across Sensing Resistor
I Loop Current in Milliamperes
R Resistance in Ohms
V Voltage in Volts
V = I X R / 1000 Formula 2
Maximum Loop Resistance for 4 - 20 mA Output
Transmitter
Rmax Maximum Loop Resistance
Vsup Supply Voltage
Rmax = (Vsup - 10 V) / 20 mA Formula 3
Gain & Zero Adjustments
Gain & Zero are set using switch 1. See Figure 3. Set-
tings are stored in EEPROM and are retained when power
is removed. Adjust Zero first to produce 4.08 mA output
0.5% of full scale). After Zero is set input 99 switch
closures and adjust the Gain (Span) to produce 19.92
mA (99.5% of full scale). Follow instructions exactly or
settings may not be stored permanently.
Switch 1 Controls
1
Set Output to full scale
2
Ramp / One Shot Mode
3
Set One One Shot Time Period
U 4
Increase parameter
D 5
Decrease parameter
Z 6
Select Zero adjust
G 7
Select Gain adjust
R 8
Reset
Zero Adjust
1. Move R to ON
2. Move U to ON
3. Move D to ON
4. Move R to OFF
5. Move U to OFF
6. Move D to OFF
7. Move Z to ON
8. Move U or D ON & OFF as required
9. Move U or D to OFF
10. Move Z to OFF.
Gain Adjust
1. Move R to ON
2. Move U to ON
3. Move D to ON
4. Move R to OFF
5. Move U to OFF
6. Move D to OFF
7. Move SW 1 to ON
10. Move G to ON
11. Move U or D ON & OFF as required
12. Move U or D to OFF
13. Move G to OFF.
14. Move SW1 to OFF
Rain Detector Time Period Transfer Function
T Time in Minutes
I Loop Current in Milliamperes
T = (I - 4mA) / 16 X 80 minutes Formula 4
Example:
I - 8 mA
T = (8mA - 4mA) /16 X 80 minutes = 20 minutes
One Shot Time Period Adjust
1. Move R to ON
2. Move U to ON
3. Move D to ON
4. Move R to OFF
5. Move U to OFF
6. Move D to OFF
7. Move SW 3 to ON
8. Move U or D ON & OFF as required
9. Move U or D to OFF
10. Move SW3 to OFF
Note: Normal program execution is suspended while
parameters are stored. Allow ten seconds for output to
stabilize after final step of calibration.
Switch 1 loads the rainfall counter to assist in calibration.
Closing Switch 1 loads 99 bucket tips.