distance specified on the diagram. The reference or sample (target) should be large
enough and positioned such that the target area of interest completely fills the field of
view of the instrument.
If optional entrance optics are included, the corresponding FOV diagrams will also
be supplied. (Refer to the document included on the CD supplied with your instrument).
4.2 Standalone Operation
Dark Measurement Overview
Important Note (Spring 2015): The PSR+3500 incorporates new fast dark
compensation and no longer supports Scaled Dark processing as performed in earlier
models.
A dark measurement is automatically taken immediately prior to taking reference
or target measurements. There is no need to manually perform a dark measurement.
The dark measurement is stored temporarily in RAM and overwritten with each new
scan.
Reflectance Measurement Overview
A reflectance measurement takes the scan of a reference (white plate) and
calculates the ratio of the target scan to that reference. Unless the instrume nt is set to
AutoDark Mode (where it takes a new dark reading with every scan) - if any of the below
conditions exist, a new dark measurement should be taken:
• After instrument power-up and warm-up, but before acquiring any reference/target
scans.
• Every 3-5 minutes thereafter; more often if time and conditions allow, or if lighting
or environmental conditions are changing.
If any of the below conditions exist, a new reference measurement should be
taken before a series of target measurements:
• Beginning of a new set of scans.
• Any change in the collection optics.
• The instrument has been idle for an extended period, or has been turned off.
• Lighting conditions have changed or are variable.
When in doubt, take a reference measurement!
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