Campbell LLAC4 User manual

LLAC4
Four-Channel, Low-Level
AC Conversion Module
Instruction Manual
23.4.12
Copyright ©2004-2012 Campbell Scientific Inc.
Printed under Licence by Campbell Scientific Ltd.
CSL 124

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About this manual
Please note that this manual was originally produced by Campbell Scientific Inc. primarily for the
North American market. Some spellings, weights and measures may reflect this origin.
Some useful conversion factors:
Area: 1 in2(square inch) = 645 mm2
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1 US gallon = 3.785 litres
In addition, while most of the information in the manual is correct for all countries, certain information
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i
Contents
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1. General Description.....................................................1
2. Specifications ..............................................................2
3. Measurements .............................................................2
4. Wiring ...........................................................................3
5. Program Examples......................................................4
Figures
1. LLAC4 four-channel, low-level AC conversion module........................... 1
2. LLAC to TTL.............................................................................................3
Tables
1. Sensor Output Frequencies ........................................................................2
2. Control Port Compatibility.........................................................................3

This is a blank page.

1
LLAC4 Four-Channel, Low-Level
AC Conversion Module
1. General Description
The LLAC4 is a peripheral device used to increase the number of low-level AC
signals a datalogger can monitor. The module enables four datalogger control
ports to emulate pulse-counting channels by converting the low-level AC signals
to the logic levels datalogger control ports require.
The LLAC4 is often used to measure up to four anemometers, and is especially
useful for wind profiling applications. Compatible wind sensors include, but are
not limited to, the 05103 Wind Monitor, 05106 Wind Monitor-MA, 05305 Wind
Monitor-AQ, 03001 Wind Sentry Set, and 03101 Wind Sentry Anemometer.
LLAC4
MADE IN USA
SN:
P1 P2 P3 P4 12V GD1 D2 D3 D4
TO DATALOGGER
FROM SENSOR G
1015
Figure 1. LLAC4 four-channel, low-level AC conversion module

LLAC4 Four-Channel, Low-Level AC Conversion Module
2
2. Specifications
Power: 8 to 16 Vdc
0.1 mA @ 12 Vdc
Signal Conditioning: Minimum AC Input Voltage versus
Output Square Wave Frequency:
Input Sine Wave
(mV RMS)
20
200
2000
5000
Output Square
Wave Range (Hz)
1.0 to 20
0.5 to 200
0.3 to 10,000
0.3 to 20,000
AC Coupling Removes DC Offset: up to ±0.5V
Input Hysteresis: 16 mV @ 1 Hz
Max AC Input Voltage:
±
20 V
Dimensions: 8.0 W x 5.4 H x 2.5 D cm
(3.1 in x 2.1 in x 1.0 in)
11.2 W x 5.4 H x 2.5 D cm
(4.5 in x 2.1 in x 1.0 in)
including base mounting flange
Cable Length: 0.6 m (2 ft)
Weight: 92 g (3.2 oz)
3. Measurements
Sensors, such as anemometers, may produce a sinusoidal AC signal output where
the frequency is proportional to the speed of rotation. This AC signal is induced
in a stationary coil by a magnet mounted on a rotating shaft.
The datalogger’s pulse channels can read this low-level AC signal directly. The
LLAC4 has signal conditioning to convert the low-level AC to a 0 to 5 volt square
wave that can be measured on the datalogger’s control ports. The frequency
response of the LLAC4 is the same as the low-level AC on the pulse inputs.
Typically, propeller type anemometers operate at higher frequencies than cup
anemometers at the same wind speed (see Table 1).
Table 1. Sensor Output Frequencies
Sensor Output @ 50m/s Type
05103 510Hz Propeller
03101 67Hz Cup
The datalogger must also be able to read these high frequency pulses on its control
ports. Table 2 shows some common dataloggers and their compatible control port
specifications.

Instruction Manual
3
Table 2. Control Port Compatibility
Datalogger Input (Hz) Control Port Measurement Type
CR1000
CR3000 400,000 C1,C2… C8 High Frequency
CR800 400,000 C1,C2,C3,C4 High Frequency
CR5000 5,000,000 C7,C8 High Frequency
CR23X 2,500 C5,C6,C7,C8 High Frequency
CR200(X) 1,000 P_LL,P_SW,C1,C2 High Frequency
CR10X 40 C6,C7,C8 Switch Closure
Comparing Table 1 to Table 2 suggests that the CR10X may not be able to read
either type of anemometer in high wind situations. However, all other dataloggers
would be appropriate choices.
4. Wiring
Most sensors that have a low-level AC output will have three wires: signal,
reference, and drain. The signal wire should go to P1 – P4 on the LLAC4 and the
reference and drain wires to a on the LLAC4. The LLAC4 also requires that
12 V be applied to its 12 V terminal and G. This power should come from the
datalogger or the datalogger’s power supply.
A low-level AC signal on P1 will be converted to a 0-5 V square wave on the D1
terminal. D1 can be wired to an appropriate datalogger control port that can make
high frequency measurements.
P1 P2 P3
FROM SENSOR TO DATALOGGER
P4 12V G D1 D2 D3 D4 G
12V
G
Control Port
G
12V
G
D1
G
DATALOGGER
SIG +
REF
DRAIN
P1
SENSOR
LLAC4
Figure 2. LLAC to TTL

LLAC4 Four-Channel, Low-Level AC Conversion Module
4
5. Program Examples
Using the CR1000, let's measure four different wind speed sensors that produce
low-level AC signals. These will include the RM Young 05103, 05106, 05305,
propeller type anemometers, and RM Young 03101 cup anemometer. Program
examples are provided for both the CR1000 and the CR200(X).
Wiring
Sensor LLAC4 CR1000 CR200(X)
05103-L Sig + Red P1
Ref Blac
k
Drain Clea
r
05106-L Sig + Red P2
Ref Black
Drain Clear
05305-L Sig + Red P3
Ref Black
Drain Clear
03101-L Sig + Black P4
Ref White
Drain Clear
12 V Red 12 V Battery +
G Black G G
D1 White C5 PLL
D2 Green C6 C1/SDI-12
D3 Yellow C7 C2
D4 Blue C8 P_SW
G Clear G G
CR1000 Example Program
'CR1000 Series Datalogger
'LLAC4 Sample Program
'Record 10-minute average wind speed in m/s for:
'1 RM Young 05103-L Wind Monitor Anemometer
'1 RM Young 05106-L Marine Wind Monitor Anemometer
'1 RM Young 05305-L AQ Wind Monitor Anemometer
'1 RM Young 03101-L Wind Sentry Anemometer
'Declare Public Variables
Public RMY05103WS
Public RMY05106WS
Public RMY05305WS
Public RMY03101WS
'Define Data Tables
DataTable (WindSpd,1,-1)
DataInterval (0,10,min,0)
Average (1,RMY05103WS,FP2,False)
Average (1,RMY05106WS,FP2,False)
Average (1,RMY05305WS,FP2,False)
Average (1,RMY03101WS,FP2,False)
EndTable
'Main Program
BeginProg
Scan (1,Sec,0,0)
PulseCount (RMY05103WS,1,15,0,1,0.098,0.0)

Instruction Manual
5
PulseCount (RMY05106WS,1,16,0,1,0.098,0.0)
PulseCount (RMY05305WS,1,17,0,1,0.1024,0.0)
PulseCount (RMY03101WS,1,18,0,1,0.750,0.20)
If RMY03101WS < 0.21 Then
RMY03101WS = 0.0
EndIf
CallTable WindSpd
NextScan
EndProg
CR5000 Example Program
'CR5000 Series Datalogger
Public Pulse_LLAC(2)
BeginProg
Scan (1,Sec,0,0)
'Measure low level AC signal (RMY 05103) on LLAC4 wired to C7 and C8 on CR5000
TimerIO (Pulse_LLAC,11000000,88000000,10,mSec) 'NOTE: Only ports CR5000 C7 and C8
'support Function 8 (frequency in Hz).
NextScan
EndProg
CR200(X) Example Program
'CR200(X) Series Datalogger
'LLAC4 Sample Program
'Record 10-minute average wind speed in m/s for:
'1 RM Young 05103-L Wind Monitor Anemometer
'1 RM Young 05106-L Marine Wind Monitor Anemometer
'1 RM Young 05305-L AQ Wind Monitor Anemometer
'1 RM Young 03101-L Wind Sentry Anemometer
'Declare Public Variables
Public RMY05103WS
Public RMY05106WS
Public RMY05305WS
Public RMY03101WS
'Define Data Tables
DataTable (WindSpd,1,-1)
DataInterval (0,10,min)
Average (1,RMY05103WS,False)
Average (1,RMY05106WS,False)
Average (1,RMY05305WS,False)
Average (1,RMY03101WS,False)
EndTable
'Main Program
BeginProg
Scan (1,Sec)
PulseCount (RMY05103WS,P_LL,0,1,0.098,0.0)
PulseCount (RMY05106WS,C1,0,1,0.098,0.0)
PulseCount (RMY05305WS,C2,0,1,0.1024,0.0)
PulseCount (RMY03101WS,P_SW,0,1,0.750,0.20)
If RMY03101WS < 0.21 Then

LLAC4 Four-Channel, Low-Level AC Conversion Module
6
RMY03101WS = 0.0
EndIf
CallTable WindSpd
NextScan
EndProg

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