Campbell Scientific LLAC4 User Manual

LLAC4 Four-Channel, Low-Level

AC Conversion Module

Revision: 3/12

Copyright © 2004-2012

Campbell Scientific, Inc.

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LLAC4 Table of Contents

PDF viewers: These page numbers refer to the printed version of this document. Use the
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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

i

This is a blank page.

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.

P1

FROM SENSOR

P2

P3

P4

12V

TO DATALOGGER

G

D1

D2

D3

D4

G

LLAC4

SN:

1015

MADE IN USA

FIGURE 1. LLAC4 four-channel, low-level AC conversion module

1

LLAC4 Four-Channel, Low-Level AC Conversion Module

2. Specifications

Power:

Signal Conditioning: Minimum AC Input Voltage versus

Input Sine Wave

AC Coupling Removes DC Offset:

Input Hysteresis:

Max AC Input Voltage:

Dimensions:

Cable Length

Weight:

8 to 16 Vdc

0.1 mA @ 12 Vdc

Output Square Wave Frequency:

Output Square

(mV RMS)

20
200
2000
5000

up to ±0.5V

16 mV @ 1 Hz

±20 V

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

0.6 m (2 ft)

92 g (3.2 oz)

Wave Range (Hz)

1.0 to 20

0.5 to 200

0.3 to 10,000

0.3 to 20,000

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.

2

LLAC4 Four-Channel, Low-Level AC Conversion Module

TABLE 2. Control Port Compatibility

Datalogger Input (Hz) Control Port Measurement Type

4. Wiring

CR1000

400,000 C1,C2… C8 High Frequency

CR3000

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.

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.

SENSOR

SIG +

REF

DRAIN

DATALOGGER

12V

G

Control Port

G

P1

12V

G

D1

G

FIGURE 2. LLAC to TTL

LLAC4

P1 P2 P3

FROM SENSOR TO DATALOGGER

P4 12V G D1 D2 D3 D4 G

3

LLAC4 Four-Channel, Low-Level AC Conversion Module

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).

Sensor LLAC4 CR1000 CR200(X)

05103-L Sig + Red P1
Ref Black
Drain Clear
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

Wiring

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

4

LLAC4 Four-Channel, Low-Level AC Conversion Module

'Main Program

BeginProg
Scan (1,Sec,0,0)
PulseCount (RMY05103WS,1,15,0,1,0.098,0.0)
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

5

LLAC4 Four-Channel, Low-Level AC Conversion Module

'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
RMY03101WS = 0.0
EndIf
CallTable WindSpd
NextScan
EndProg

6

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