Element descriptions

In this section we break down each subset of the XML tags. We begin with the root-level tags and then describe the subordinate tags in greater detail.

Table 2‑1. The root tag for all XML communication is <LI850> or <LI830>.
Root Parent Value Definition
<LI850>
or
<LI830> 		<DATA> Float See Data tags.
<AUXDATA> Float See Auxiliary data tags.
<CFG> Various See Configuration tags.
<PUMP> Various Pump status. See Pump tags.
<SOURCE> Integer Hours the source has operated. See Source tag.
<CAL> Various See Calibration tags.
<POLY> Various See Polynomial tags.
<RS232> True | False See RS-232 serial tags.
<VER> String Software version. See Software version.
<SERIALNUM> String Serial number. See Serial number.
<ACK> True | False Acknowledgment of a command.
<ERROR> String Error. Includes a message.
<TECH> Various Diagnostics. See Tech tags.

Sending this command will return the full configuration file and measured values that are configured to be sent over the serial connection.

<LI850>?</LI850>

The instrument will reply by sending the data and the confirmation message:

<LI850><ACK>TRUE</ACK></LI850>

Data tags

The <DATA> tag contains all data values sent from the instrument. All of the elements within <DATA> are readable only. The <H2O>-related tags apply to the LI-850 only.

Table 2‑2. Elements available in the <DATA> tag.
Root Parent Children Values R/W Comments
<LI850> or <LI830> <DATA> <CO2> Float R CO2 in ppm
<CO2ABS> Float R CO2 absorption
<H2O> Float R H2O in mmol/mol
<H2ODEWPOINT> Float R H2O in °C
<H2OABS> Float R H2O absorption
<CELLTEMP> Float R Cell temperature
<CELLPRES> Float R Cell pressure
<IVOLT> Float R Input voltage
<FLOWRATE> Integer R Measured flow rate
<RAW> See Raw data tags

To query the data, send:

Copy 
<li850>
    <data>?</data>
</li850>

If a data value is not returned, it is probably "turned off" in the serial data stream. See RS-232 serial tags for more information.

Raw data tags

The raw detector counts can be retrieved by querying the parent <data> tag. The <h2o>-related tags apply to the LI-850 only. To see the raw detector counts, send:

Copy 
<li850>
    <data>
        <raw>?</raw>
    </data>
</li850>
Table 2‑3. Elements within the <RAW> tag. These are raw detector readings.
Root Parent Parent Children Values R/W
<li850>

or

<li830> 		<data> <raw> <co2> Integer R
<co2ref> Integer R
<h2o> Integer R
<h2oref> Integer R

To disable the raw data from the serial data stream, you have to modify the instructions under the <rs232> tag. So, send:

Copy 
<li850>
    <rs232>
        <raw>false</raw>
    </rs232>
</li850>

Auxiliary data tags

The <AUXDATA> tag contains all auxiliary data values that can be retrieved from the instrument. All of the elements within the <AUXDATA> tag are readable only.

Table 2‑4. These tags are under <AUXDATA>.
Root Parent Children Values R/W
<li850>

or

<li830> 		<auxdata> <pca> Float R
<pha> Float R
<psi> Float R
<bb_eff> Float R

To query the auxdata, send:

Copy 
<li850>
    <auxdata>?</auxdata>
</li850>

RS-232 serial tags

The <RS232> tag is where you set which values are output in <DATA>. TRUE means that the value will be sent; FALSE means it will not be sent. The <H2O>-related tags apply to the LI-850 only.

Table 2‑5. Setting the <RS232> values will determine which values are output in <DATA>.
Root Parent Children Values R/W Comments
<LI850>
or
<LI830> 		<RS232> <CO2> True | False R/W CO2 in ppm
<CO2ABS> True | False R/W CO2 absorption
<H2O> True | False R/W H2O in mmol/mol
<H2ODEWPOINT> True | False R/W H2O dew point
<H2OABS> True | False R/W H2O absorption
<CELLTEMP> True | False R/W Cell temperature
<CELLPRES> True | False R/W Cell pressure
<IVOLT> True | False R/W Input voltage
<ECHO> True | False R/W Echo commands sent
<STRIP> True | False R/W Strip XML
<FLOWRATE> True | False R/W Flow rate

Sending this command will configure the output rate and the variables output over the serial connection.

Copy 
<LI850>
    <CFG>
        <OUTRATE>1</OUTRATE>
    </CFG>
    <RS232>
        <CO2>TRUE</CO2>
        <CO2ABS>TRUE</CO2ABS>
        <h2o>false</h2o>
        <h2odewpoint>false</h2odewpoint>
        <h2oabs>false</h2oabs>
        <CELLTEMP>TRUE</CELLTEMP>
        <CELLPRES>TRUE</CELLPRES>
        <IVOLT>TRUE</IVOLT>
        <ECHO>FALSE</ECHO>
        <STRIP>FALSE</STRIP>
        <flowrate>false</flowrate>
    </RS232>
</LI850>

Configuration tags

Configuration tags are used to apply settings to the instrument.

Table 2‑6. Elements within the <CFG> tag.
Root Parent Children Values R/W Comments
<li850>

or

<li830> 		<cfg> <outrate> 0.5 to 20 R/W Output data every N seconds (0.5 second increments).
<heater> True | False R/W Turn heater on/off.
<pcomp> True | False R/W Pressure compensation on/off.
<filter> 0 to 20 R/W Set a 0 to 20 second filter for data logging.
<bench> 14 R Bench length (not used).
<alarms> Alarm settings. See Alarm tags.
<dacs> DAC output settings. See DAC tags.

Sending this command will set the output rate to 1 per second, turn the optical bench heater on, apply the pressure compensation, and turn off data filtering:

Copy 
<LI850>
    <CFG>
        <OUTRATE1</OUTRATE>
        <HEATER>TRUE</HEATER>
        <PCOMP>TRUE</PCOMP>
        <FILTER>0</FILTER>
    </CFG>
</LI850>

Alarm tags

Alarm tags configure the alarm states.

Root Parent Parent Children Values R/W Comments
<li850>

or

<li830> 		<cfg> <alarms> <enabled> True | False R/W Enable alarms
<source> co2 | h2o R/W Channel (CO2, H2O)
<high> Float R/W High alarm on at this value
<hdead> Float R/W High alarm off at this value
<low> Float R/W Low alarm on at this value
<ldead> Float R/W Low alarm off at this value

To configure the alarms, send:

Copy 
<LI850>
    <CFG>
        <ALARMS>
            <ENABLED>{bool}</ENABLED>
            <SOURCE>H2O | CO2<SOURCE>
            <HIGH>{float}</HIGH>
            <HDEAD>{float}</HDEAD>
            <LOW>{float}</LOW>
            <LDEAD>{float}</LDEAD>
        </ALARMS>
    </CFG>
</LI850>

DAC tags

DAC tags configure the analog outputs.

Root Parent Parent Children Values R/W Comments
<li850>

or

<li830> 		<cfg> <dacs> <range> 2.5 | 5.0 R/W Output voltage. 0 to 2.5V or 0 to 5.0V
<d1> Various R/W CO2 | H2O | H2ODEWPOINT | CELLPRES | CELLTEMP | NONE from DAC1
<d1_0> Float R/W Value where DAC1 outputs 0V
<d1_F> Float R/W Value where DAC1 outputs full scale
<d2> Various R/W CO2 | H2O | H2ODEWPOINT | CELLPRES | CELLTEMP | NONE from DAC2
<d2_0> Float R/W Value where DAC2 outputs 0V
<d2_F> Float R/W Value where DAC2 outputs full scale

To configure the DACs, send:

Copy 
<LI850>
    <CFG>
        <DACS>
            <RANGE>{2.5|5.0}</RANGE>
            <D1>{NONE|CO2|H2O|H2ODP|CELLTEMP|CELLPRES}</D1>
            <D1_0>{float}</D1_0>
            <D1_F>{float}</D1_F>
            <D2>{NONE|CO2|H2O|H2ODP|CELLTEMP|CELLPRES}</D2>
            <D2_0>{float}</D2_0>
            <D2_0>{float}</D2_F>
        </DACS>
    </CFG>
</LI850>

Pump tags

Pump tags are used to control the LI-COR pump.

Table 2‑7. Tags used to control the pump (if applicable).
Root Parent Children Values R/W Comments
<li850>

or

<li830> 		<pump> <enabled> True | False R/W Turns pump on/off
<time> Integer R/W Number of hours pump has run
<status> Integer R/W Pump and flow meter present? (0 = pump, 1 = flow meter, 2 = pump and flow meter, 3 = neither)

To enable the pump, send:

Copy 
<li850>
    <PUMP>
        <ENABLED>true</ENABLED>
    </PUMP>
</li850>

To reset the pump hours (after replacing it, for example), send:

Copy 
<li850>
    <PUMP>
        <HOURS>0</HOURS>
    </PUMP>
</li850>

Source tag

The source tag indicates the number of hours that the optical source has operated. This information is useful for diagnostic purposes.

Root Parent Children Values R/W Comments
<li850>

or

<li830> 		<source> <time> Integer R/W Number of hours of source operation

To read the source time, send:

Copy 
<li850>
    <source>?</source>
</li850>

Calibration tags

Calibration tags are used to start a calibration or read calibration information. When calibrating, <date> must be paired with a <co2zero> or a <co2span>, or a <h2ozero> or <h2ospan>. The <h2o>-related tags apply to the LI-850 only.

Table 2‑8. Tags used to calibrate the instrument.
Root Parent Children Values R/W Comments
<li850>

or

<li830> 		<cal> <date> 20 character date W The current date
<H2OZERO> True | False W Start H2O zero
<H2OSPAN> Float (h2o) W Start the H2O span 1
<H2OSPAN2> Float (h2o) W Start the H2O span 2
<H2OLASTZERO> 20 character date R Date of last H2O zero
<H2OLASTSPAN> 20 character date R Date of last H2O span
<H2OKZERO> Float R/W Calibration constant
<H2OKSPAN> Float R/W Calibration constant
<H2OKSPAN2> Float R/W Calibration constant
<CO2ZERO> True | False W Start a CO2 zero
<CO2SPAN> Float (co2 ppm) W Start the CO2 span 1
<CO2SPAN2> Float (co2 ppm) W Start the CO2 span 2
<CO2LASTZERO> 20 character date R Date of last CO2 zero
<CO2LASTSPAN> 20 character date R Date of last CO2 span
<CO2KZERO> Float R/W Calibration constant
<CO2KSPAN> Float R/W Calibration constant
<CO2KSPAN> Float R/W Calibration constant

Calibration instructions are given in Zero and span settings. To read the current calibration, send:

Copy 
<li850>
    <cal>?</cal>
</li850>

Polynomial tags

Polynomial tags contain calibration information from the instrument. The values included are determined at the factory. Do not change the polynomial values because that will adversely affect the analyzer performance. The <h2o>-related tags apply to the LI-850 only.

Table 2‑9. Calibration polynomial related tags.
Root Tag Parent Children Value(s) R/W Comments
<li850>

or

<li830> 		<poly> <date> Serial number and ISO date R/W Serial number and factory calibration date: HGA XXXX yyyy-mm-dd
<bb> Float R/W Band broadening value
<xs> Float R/W Cross sensitivity value
<co2> <a1><a2>

<a3><a4> 		R/W Floating point coefficients for the CO2 calibration inverse rectangular hyperbola
<h2o> <a1><a2>

<a3> 		R/W Floating point coefficients for the H2O calibration polynomial
<press> <a0><a1> R/W Floating point coefficient for CO2 pressure correction

To read the polynomial information, send:

Copy 
<li850>
    <poly>?</poly>
</li850>

Tech tags

Tech tags indicate information about the instrument, including pump and optical source information. They are not included in the status information returned by the instrument. You can poll the tech information specifically.

Table 2‑10. Tags used to read information about the pump and source.
Root Parent Parent Children Values R/W Comments
<li850>

or

<li830> 		<tech> <pump> <MODEL> String R/W Pump model
<Ki> Integer R/W Integer value for PID control
<Kp> Integer R/W Proportional value for PID control
<Kd> Integer R/W Derivative value for PID control
<OFFSET> Integer R/W Pump control offset
<GAIN> Integer R/W Pump control gain
<FLOW> 0 to 1.0 R/W Flow setting in LPM
<SOURCE> <VOLTAGE> 0 to 5.0 R/W Source voltage setting

To read the tech information, send:

Copy 
<li850>
    <tech>?</tech>
</li850>