Calibrating the FMS

HOW TO CALIBRATE THE FMS:
To work gas tanks:

• Open valve, connect tube and check flow rate before connecting to the FMS
• flip uper left switch up so it is at baseline, calibrate system (see below)
• Close tank, depressurize regulator for storage and turn off

Calibrate/Setting the water vapor span:

• Before hooking any tubes up check that its air NOT water flowing through tubing
• Flip the upper left switch to ‘baseline’ (instead of ‘chamber’) on FMS
• Turn the mode dile on the FMS to dew point to calibrate (ONLY IF USING A DPG/LI-COR)
• Hook up a tube from FMS baseline to H2O “gas” with a vent on the tubing
• There are 3 ways to check the lower span (0):
  • Dry gas tank with the factory CO2 span (recommended option)
  • O2 dilution method as described in the manual (see very bottom of this doc)
    e.g., O2 is normally at ~21%. When you add water to the system O2 decreases by an expected/calculatable amount
  • Calibrate against a reference humidity meter (e.g., DPG/LI-COR)

How to check the accuracy of the upper H2O span:

• Use the factory set upper limit
• If using a Dew Point Generator (DPG)/LI-COR at a set humidity level:
  change WV units to Dew Point for the calibration step only (then change back to the units we wish to measure [probably apa or abs/rel. humidity])
• Nalgene set up (last resort)
  • Tube leading to cage cannot be in the water
  • Theory: if you increase the pressure you decrease the humidity
  • ****CAUTION: the water must be cooler than the rest of the system!!!
  • Recommended: 3-5°C lower then room temp
  • Determine temperature of water
  • Set flow to 100-500 ml/min
  • Before hooking tube up check that its air NOT water flowing through

Calibrate/Setting O2 span:

• You will need a tank of 21% O2, 0% CO2, the rest Nitrogen
• You only need to set the upper span of this
• Check the label on gas tank for percent O2 (should be ~21%)
• Connect gas -> grey connector -> bevaline tubing -> T connector -> baseline port
• IN THE FIELD, you can set Fixed span by using outside air and a scrubber, this can be water or CO2 scrubber or both
  • The usual outside air is usually 20.95% O2 so this is what you would set
• There are other ways in the manual if you want

If you have a gas 21% O2, 0% CO2, the rest Nitrogen you can set Vary span:

• Flip the switch to baseline
• Turn on the gas very low and check flow rate manually before hooking the tubes up to baseline
• Flow needs to be at least 250, if its lower then you will be using the room air not the tank air
• Once upper O2 range (on the FMS screen) reaches the same value of O2 as is in the tank (value on the tag) click the enter button to set the CO2 span
• Don’t try to set O2 above 25% because it requires a bunch of other things that are talked about in the manual

Oxygen Range Mode:

• This mode allows you to select the analog oxygen range. Three ranges are available, corresponding to 0 – 5V at the analog output:

    0 – 100		= V * 20
    0 – 25		= V * 5
    19 – 21.5		= 19 + (V * 0.5)

Calibrating/setting CO2 span:

• You will need a tank of 1% CO2 balanced with air
• Connect gas -> grey connector -> bevaline tubing -> T connector -> baseline port
• Flip the switch to baseline
• Turn on the gas very low before hooking the tubes up to baseline
• Flow needs to be more than 250, if its lower then you will be using the room air not the tank air
• Prior to setting CO2 you will need to run CO2 free air through the sensor for several minutes

Setting CO2 lower span (checking zero):

• This must be done with CO2 free air!!!
• Ways to achieve that:
  • Ascarite
  • Nitrogen gas
  • Maybe the O2 tanks? (tbd)

Setting the CO2 upper span:

• NOTE: If you are out in the field (this is not recommended!)however:
  • *Take dry air from a CO2 pollution source
    Trucks
    People
• If you have tank gas (and you should):
  • Turn on the gas very low before hooking the tubes up to baseline
  • Flow needs to be more than 250, if its lower then you will be using the room air not the tank air
  • Prior to setting upper span you should run CO2 air through the sensor for several minutes
  • Adjust the CO2 upper span so it matches exactly what is written on the tag attached to the tank
    *** don’t ever use CO2 span control to zero the CO2 sensor!!

CO2 Range Mode:

• This mode allows you to select the analog CO2 range. Nine ranges are available, corresponding to 0 – 5V at the analog output:

  ​​​​​​  0 – 10 		= V * 2
  ​​​​​​  0 – 5		= V * 1
  ​​​​​​  0 – 2		= V * 0.4
  ​​​​​​  0 – 1		= V * 0.2
  ​​​​​​  0 – 0.5		= V * 0.1
  ​​​​​​  0 – 0.2		= V * 0.04
  ​​​​​​  0 – 0.1		= V * 0.02
  ​​​​​​  0 – 0.05		= V * 0.01
  ​​​​​​  0 – 0.02		= V * 0.004
  

• V is the analog output in volts. The same numbers apply irrespective of the units selected (% corrected or uncorrected, or kPa). The analog output appears at the MASS FLOW BNC connector on the front panel This mode has no effect on the displayed values.

O2 dilution (from FMS manual):

• Set the zero on the RH-300 with dry N2 (or mg perchlorate scrubbed air)
• Set the span on the FC-10 using your usual span gas (e.g. scrubbed air or tank gas)
• Switch the flow of gas through the RH-300 and FC-10 to ambient air with no scrubber.
• Flow (wet) air through the FC-10 for 2-3 minutes and get a mean value for O2 %
• Add the scrubber column and wait about 3 minutes for the O2 to settle at a new value. Record the mean dry O2 % and the barometric pressure.
• The water vapor pressure in kPa is calculated from the formula:
  WV = BP*(dryO2-wetO2)/(dryO2)
• Set the Units on the RH-300 to “WV Pressure’. Enter the value from step F as the span for the RH-300.
  *******Once calibrated change the mode back to ______ (this is researchers’ choice and we should decide this and move on with our lives)