STP ADJUSTMENT... 'f' This window
contains a small calculator for adjusting a measured flow rate to conditions
of standard temperature and pressure (STP). STP conversion is necessary
for gas exchange calculations. Although the gas exchange routines
will perform an STP adjustment, this window's algorithm is more versatile:
You can select either a measure of uncorrected flow rate (in ml/min)
or a cumulative volume (ml) over a measured time period (seconds).
The latter method is most useful for dry volume meters, bubble meters,
In addition to barometric pressure, you can account for any internal
pressure within the gas flow meter (which may occur if you are using relatively
high flow rates and/or small-diameter tubing). Internal pressure
can be in units of torr, PSI (pounds/square inch), KPa (Kilopascals), or
mm of water (if you are using a water manometer).
You can adjust the calibration temperature of your flow instrument.
Most such devices are calibrated for a temperature of zero °C, but
some (like Singer dry volume meters) may be calibrated for 20 °C or
The '∑' button adds the current value into an internal
register that is used to compute an average value (displayed with the 'show
average' button). These functions correctly account for whether
the display is set for standard cubic centimeters/min (SCCM) or standard
liters per minute (SLPM).
The 'store flowrate' button saves the currently displayed STP
flow rate as the default flow rate for gas exchange calculations (in units
of SCCM). Either an averaged flow rate or an individually-computed
value are accepted, and the display setting (SCCM or SLPM) is taken into
account. In addition to saving STP flow, this button also stores
a barometric pressure of 760 torr and a meter temperature of 0 °C (this
is necessary to retain the accuracy of the STP conversion when computing