Select the bytes to read parameter of the TCP Read block to match or exceed the size of the data message coming from the instrument.
Serial Port Labview Visa Serial Or EthernetSince most LI-COR environmental instrument have some sort of digital interface such as serial or Ethernet, you can communicate, control, and collect data from these instruments using LabVIEW.The purpose of this application note is to provide a primer for developing LabVIEW scripts for interacting with some LI-COR gas analyzers.
Serial Port Labview Visa Drivers Or CodeThis note does not provide drivers or code to collect or process the data. The example scripts included are very basic scripts and dont perform any particular function other than read in the data and display it. Serial Port Labview Visa Manual To FullySeveral aspects of the instrument grammar is also used in the scripts and it is essential to refer back to the grammar section of the instrument user manual to fully understand or modify the implementation. The serial port settings on the 62XX instrument should be set using keypad FCT17. The variables that have to be measured can be set by sending the 13x,x,x,x,x,x,x,x,x,x, where x is the channels you want to output. By writing 12 to the serial port along with a carriage return (serial write block), the data will be sent out and it can be read by using the serial read block. ![]() The instrument is polled for data and it can be read continuously at a rate set by a LabVIEW timer. In the example below, channels 22, 23 29, 32, 33, 38, 39, 42 and 43 are configured to be sent out through the serial port. The serial setting property node is used to estimate the number of bytes at the port and then this information is fed to the serial read block to read in the data. To parse out and plot the data, search and replace vi and spread sheet string to array vi are used. Ethernet connectivity is much more flexible and allows connectivity to a device on a home or remote network. The instrument transmits data at a fixed output rate, which is configured in the instrument settings. Since network data transmission is susceptible to latencies, the best practice is to use the time stamp from the instrument, rather than time stamping the data based on arrival to the computer. In this way you can expect predictable amount of data from the instrument and then read the expected number of bytes. The LI-7200 and LI-7500ARS communicates through TCP port 7200. LabVIEW TCP write and read blocks can be used to interact with the instrument and read the data. The instrument grammar gives the option to add a carriage return and line feed to the end of a data stream. Enable this option in the instrument, then utilize the CRLF mode in the TCP read block. This configuration will wait for a carriage return followed by a line feed in the data stream to stop reading the data. Set the interactive mode in the instrument to false (IM FALSE) to suppress acknowledgments and other messages from the instrument. Configure the desired outputs through the outputs tab in the instrument software.
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