Wiring an RM Young Sonic Anemometer To a LI-COR Eddy Covariance System

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Instructions for connecting an RM Young Anemometer to a LI-COR EC system.

The RM Young 81000 sonic anemometer is one of the many sonic anemometers that can be used with a LI-COR EC system. Since the RM Young provides a junction box, wiring it to the LI-7550 is straightforward. The Analog Input/output cable (Part Number 392-10109) provided with the LI-7550 spare parts kit can be used instead of the Auxiliary Sensor Interface Unit. You can wire the bare lead ends directly to the junction box of the RM Young 81000 and then connect the other end directly to the LI-7550 Auxiliary Input.

The wiring is described in the table at right, adapted from Page 8 of the RM Young 81000 manual. The table also includes some suggestions on how the RM Young 81000 and the LI-7500A/LI-7200 should be configured. By default, the 81000 factory analog outputs are wind speed, direction, elevation and sonic temperature. These should be changed to appropriate outputs for collecting data through the LI-7550 analog input channels. The instrument has to be configured through a terminal program such as Hyper Terminal or Tera Term using a baud rate of 38400. After applying power, the data should stream in, and sending the ESC character (ASCII 27) in three quick successions should take you to the command mode.

Table 1‑1. RM Young Anemometer connection settings. Range on all channels should be 0-5000 mV. Serial output format set to (CUSTOM) Output Rate = 10 Hz or 20 Hz (No averaging), depending on data logging rate
Pin Number Channel Wire Color RM Young Junction RM Young Voltage Output Format 2 - U, V, W, and Sonic Temp. LI-7500A/RS and LI-7200/RS Auxiliary Input Settings
Pin 1 AUX1+ White V1 Scale -30 to 30 m/s Type: U, Units: m/s
m=12, b=-30
Pin 2 AUX1- Brown VREF    
Pin 3 AUX2+ Green V2 Scale -30 to 30 m/s Type: U, Units: m/s
m=12, b=-30
Pin 4 AUX2- Yellow VREF    
Pin 5 AUX3+ Grey V3 Scale -30 to 30 m/s Type: U, Units: m/s
m=2, b=-5
Pin 6 AUX3- Pink VREF    
Pin 7 AUX4+ Blue V4 Fixed scale Type: Ts, Units: k
m=20, b=220
Pin 8 AUX5- Red VREF    
Pin 9 +5V Orange Not used    
Pin 10 GND Tan Not used    
Pin 11 GND Black Not used    
Pin 12 GND Violet Not used