Vaisala LT31 - Page 247

Chapter 6 ______________________________________________________________ Maintenance
VAISALA ______________________________________________________________________ 247
stability of the current measurement and any change in prevailing
visibility conditions.
- Reference: Entering the Linearity Test menu stores current MOR
reading and transmittance. The reference value is valid as long as it
remains in the Linearity Test menu or until another prevailing
visibility/transmittance is chosen to be the new reference.
- Calculated: When giving a filter value, the target values are
calculated based on the reference values and the filter value. When no
filter value is available, reference and calculated values are the same.
- Measured: Currently measured values.
- Deviation: Deviation between measured and calculated values. The
deviation is given both, as absolute (abs.) and relative (rel.) values.
- 2-minutes-Variation-versus-current-Measurement: The 2-minutes-
Variation-versus-current-Measurement is the minimum (down) and
maximum (up) visibility compared to the current, 'Measured' data.
The 2-minutes-Variation-versus-current-Measurement is given only
when the latest action (entering the menu page, applying the filter,
removing of filter) is longer than two minutes ago. Otherwise it is
replaced by dashes ('---------'). The values are given as absolute
differences.
- Reference-Quality-Indication (Ref. Quality): The Reference-
Quality-Indication is a three step quality indication of the prevailing
transmittance compared to the formerly taken reference transmittance.
The Reference-Quality-Indication is given only when, by procedure,
no filter is applied and latest action (entering the menu page,
removing of filter) is longer than two minutes ago. Otherwise it is
replaced by dashes ('--------'). The Reference-Quality-Indicator is
reported as
- 'very steady, +/- 0.05% abs.' when
9995.0/0005.1/
min2min2



refMINrefMAX
TTTT or
- 'steady, +/- 0.50% abs.' when
995.0/005.1/
min2min2



refMINrefMAX
TTTT or
- otherwise as 'unsteady, >+/- 0.5% abs.'
- APPLIED FILTER VALUE: In addition, the filter value taken into
account for calculated values and deviation, is displayed.
The deviation values are used to evaluate or verify the measurement
performance of the LT31 system.