Xylem SDI-12 Data Logger iRIS 220, iRIS 320, iRIS 350, iRIS 150, iRIS 300 - Manual (Page 61)

55 iQuest (NZ) Ltd - PO Box 15169, Hamilton, New Zealand Tel: +64 7 857-0810 Fax: +64 7 857-0811 Email: [email protected]
6.7 Connecting Analog Wind Instruments
Many wind measurement instruments operate in an analog mode. The wind direction sensor is usually a
potentiometer which is driven by the buffered 5.0V output from the iRIS. The wiper signal is connected to
one of the analog inputs. As the iRIS analog inputs have low pass filtering included, there is no need for
external components to remove noise. The anemometers usually provide a switched pulse signal from a
transistor or opt-coupler. This drives a digital input, operating in counter mode and the frequency is
measured, scaled and logged.
For the anemometer to operate correctly, the pulse amplitude must be at least 3V p-p. Some
instruments emit a low level a.c signal in the order of millivolts. In these cases a simple
transistor switch to create a suitable pulse must be included. Please contact iQuest for
details.
The diagram below shows a typical installation.
TOP iRIS I/O Connector
BOTTOM
A typical sensor configuration example for this type of installation is shown below. The instruments are a
Vector A101M wind speed sensor providing pulses that are converted to metres/sec and a Vector W200P
wind direction sensor. The speed and direction are averaged and the results logged every 10 minutes and
the wind speed min and max (lull and gust) are also logged.
AI4
AI3
AI2
AI1
AGND
AOUT
DI2
DI1
DO2
DO1
SDI-12
DGND
12V+
GND (-)
VIN+
GND (-)
- +
External
12V Battery
(Optional)
Wind
PULSE Speed
+12V Sensor
0V
Charging source
e.g. solar panel
SUPPLY
SIGNAL
GND
Wind
Direction
Sensor
* Sensor 1 Cfg
(Now: 3.11)
0 Exit
1 Source [9: Freq 1]
2 Name [Wind Spd]
3 Mode [Period Avg+Min+Max]
4 Multiplier [ 0.010]
5 Offset [ 0.000]
6 Log Multiplier [ 10]
7 Log Rate [10min]
8 Alarms
9 Data * Sensor 2 Cfg
(Now: 176.00)
0 Exit
1 Source [1: Analog1]
2 Name [Wind Dir]
3 Mode [Scalar Avg]
4 Multiplier [ 71.800]
5 Offset [ 0.000]
6 Log Multiplier [ 1]
7 Log Rate [10min]
8 Alarms
9 Data