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LLAC4 Four-Channel, Low-Level AC Conversion Module
2. Specifications
3. Measurements
2
Power:
Signal Conditioning:
AC Coupling Removes DC Offset:
Input Hysteresis:
Max AC Input Voltage:
Dimensions:
Cable Length:
Weight:
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
05103
510Hz
03101
67Hz
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.
8 to 16 Vdc
0.1 mA @ 12 Vdc
Minimum AC Input Voltage versus
Output Square Wave Frequency:
Input Sine Wave
(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)
Type
Propeller
Cup
Output Square
Wave Range (Hz)
1.0 to 20
0.5 to 200
0.3 to 10,000
0.3 to 20,000
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