LI7700 (Measure LI-7700 Gas Analyzer)
The LI7700 instruction is used to measure an LI-7700 LI-COR Open Path CH4 gas analyzer.
Syntax
LI7700 ( Dest, Reps, SDMAddress, LI7700Cmd )
Example
The following example shows the use of the LI7700 instruction.
'Declare Variables
Public LI(5)'Variable array for storing output
Alias LI(1) = CH4D'Create aliases for array elements
Alias LI(2) = Pressure
Alias LI(3) = Temp
Alias LI(4) = Diag
Alias LI(5) = RSSI
Units CH4D = mmol/m^3'establish units for dimensional outputs
Units Pressure = kPa
Units Temp = C
BeginProg
Scan (1,Sec,3,0)
'get data from LI-7700 CH4 gas analyzer
LI7700(LI,1,3,1)
NextScan
EndProg
Remarks
The LI7700 instruction is used to communicate with the LI-7700 via SDM.
Parameters
Destination
The input variable name in which to store the data from each LI-7700 associated with this instruction. The length of the input variable array will depend on the number of repetitions and on the selected command.
| Command | Input Variable length per LI-7700 |
|---|---|
| 0 | 3 |
| 1 | 5 |
| 2 | 9 |
| 3 | 13 |
| 4 | 17 |
| 5 | 3 |
| 6 | 7 |
| 7 | 9 |
Type: Array
Reps
Determines the number of gas analyzers with which to communicate using this instruction. The gas analyzers must have sequential SDM addresses if the Reps parameter is greater than 1.
Type: Constant integer (or expression that evaluates as a constant).
SDMAddress (Address of Device)
Defines the address of the device with which to communicate. Valid SDM Synchronous Device for Measurement. A processor-based peripheral device or sensor that communicates with the datalogger via hardwire over a short distance using a protocol proprietary to Campbell Scientific. addresses are 0 through 14. Address 15 is reserved for the SDMTrigger instruction.
Some SDM instructions support repetitions. If a Reps parameter is present and it is greater than 1, the data logger will increment the SDM address used in the instruction for each subsequent device with which it communicates.
LI7700Cmd
Requests the data to be retrieved from the sensor. The command is sent first to the device specified by the SDMAddress parameter. If the Reps parameter is greater than 1, subsequent LI-7700s will be issued the command with each repetition. The results for the command will be returned in the array specified by the Dest parameter. A numeric code is entered to request the data:
| Code | Description |
|---|---|
| 0 | CH4D (mmol/m^3), pressure (kPa), Temp (C) |
| 1 | CH4D (mmol/m^3), pressure (kPa), Temp (C), diagnostic, RSSI |
| 2 | CH4D (mmol/m^3), pressure (kPa), Temp (C), diagnostic, RSSI, AUX1, AUX2, AUX3, AUX4 |
| 3 | CH4D (mmol/m^3), CH4 (umol/mol), pressure (kPa), Temp (C), diagnostic value, RSSI, AUX1, AUX2, AUX3, AUX4, AuxTc1, AuxTc2, AuxTc3 |
| 4 | CH4D (mmol/m^3), CH4 (umol/mol), pressure (kPa), Temp (C), diagnostic, RSSI, AUX1, AUX2, AUX3, AUX4, AuxTc1, AuxTc2, AuxTc3, AUX5, AUX6, AUX7, AUX8 |
| 5 | RSSI, diagnostic, drop rate |
| 6 | RSSI, diagnostic, heater, drop rate, OpticsRH (%), LCTActual, LCSetPT |
| 7 | RSSI, heater, RefRSSI, drop rate, LCTActual, LCTSetPT, BCTActual, BCTSetPT, OpticsRH (%) |