LLAC4 4-Channel Low-Level AC-Conversion Module
Expands Capacity
Increases number of signals data logger can monitor
weather applications water applications energy applications gas flux and turbulence applications infrastructure applications soil applications


The LLAC4 is a small peripheral that you can use to increase the number of low-level ac signals that your data logger can monitor. The LLAC4 is often used to measure up to four anemometers, and it is especially useful for wind profiling applications.

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Benefits and Features

  • Ideal for applications that require high numbers of pulse channels, but fewer control ports, such as in wind prospecting


Detailed Description

The LLAC4 enables four data logger control ports to emulate pulse-counting channels by converting the low-level ac signals to logic levels read by the control ports. To use the LLAC4, the data logger control ports must accept high frequency pulses. The LLAC4 typically measures anemometers but can measure other sensors that output pulse counting signals. 

Minimum AC Input Voltage versus Output Square Wave Frequency

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


Function Increases the number of low-level ac signals that a data logger can monitor.
Number of Channels 4
Power 0.1 mA (@ 12 Vdc)
Input Hysteresis 16 mV (@ 1 Hz)
AC Coupling Removal of DC Offset ≤ ±0.5 V
Maximum AC Input Voltage ±20 V
Cable Length 0.6 m (2 ft)
  • 5.4 x 8.0 x 2.5 cm (2.1 x 3.1 x 1.0 in.) without base mounting flanges
  • 5.4 x 11.2 x 2.5 cm (2.1 x 4.5 x 1.0 in.) with base mounting flanges
Weight 92 g (3.2 oz)


Note: The following shows notable compatibility information. It is not a comprehensive list of all compatible or incompatible products.

Data Loggers

Product Compatible Note
21X (retired)
CR10 (retired)
CR1000 (retired)
CR10X (retired)
CR200X (retired) To be compatible with the CR200X, the low-level ac signals must not exceed 1 kHz.
CR206X (retired) To be compatible with the CR206X, the low-level ac signals must not exceed 1 kHz.
CR211X (retired) To be compatible with the CR211X, the low-level ac signals must not exceed 1 kHz.
CR216X (retired) To be compatible with the CR216X, the low-level ac signals must not exceed 1 kHz.
CR23X (retired)
CR295X (retired) To be compatible with the CR295X, the low-level ac signals must not exceed 1 kHz.
CR3000 (retired)
CR500 (retired)
CR5000 (retired)
CR510 (retired)
CR800 (retired)
CR850 (retired)
CR9000 (retired)
CR9000X (retired) It is necessary to use the CR9071E module with the CR9000X and LLAC4.


Product Compatible Note
05103-45-L (retired)
05106-L (retired)

Additional Compatibility Information

Data Logger Considerations

The LLAC4 works only with data loggers whose control ports can accept high frequency pulses. The CR23X has four control ports that can be used (5, 6, 7, and 8); the CR200X-series control ports are compatible but are limited to inputs of 1 kHz.


The LLAC4 typically measures anemometers. Compatible anemometers include the Wind Monitors, 03002 Wind Sentry Set, and 03101 Wind Sentry Anemometer. (The 014A Anemometer and 034B Windset are not compatible.) The LLAC4 can also measure other sensors that output pulse counting signals.


LLAC4 Program Example (2 KB) 05-21-2024

Description: Includes two programs, one for a CR1000X and one for a CR350. Both programs measure three different wind speed sensors that produce low-level AC signals. The sensors used are the RM Young 05103 and RM Young 05305 propeller-type anemometers, as well as the RM Young 03101 cup anemometer.

Frequently Asked Questions

Number of FAQs related to LLAC4: 1

  1. No. But using a LLAC4 will convert the ac signal for up to four 03101-L sensors (and other ac output anemometers) to individual 0 to 5 Vdc TTL level square wave outputs. For more information, see the LLAC4 specification information

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