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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
Output Square
(mV RMS)
Wave Range (Hz)
20
1.0 to 20
200
0.5 to 200
2000
0.3 to 10,000
5000
0.3 to 20,000
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
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