Granuloshop Lab: Laser Cell # 1

Set-Zero (blank)

Set-zero = signal received by diffractometer without sample, then substracted from signal => sample specific signal. Too high = Warning!

• •Electronics fault (rare)
• • Turbid liquid (bubbles, contamination)
• • Noise due to the cell: stains, scratches, ...

Look at set-zero: if only a very small deviation triggered the alarm, you may still decide to ignore the warning

Turbid liquid

several, easy to identify possible causes

• •  some of previous sample remains: rinse again
• •  visible bubbles: surfactant: rinse again
• •  micro-bubbles: temp. difference water/instrument or check waterproof tightness
• •  non-mixing liquids: rinse with mixing liquids

Array calibration

Your instrument will serve many , many years. The natural aging of detectors must be corrected on a regular basis.
Do not forget to perform the uniform (array) calibration (at least once / 3 months)

• •  Do 'laser align' (recommended: auto-align always on)
• •  duration: < 1 Min.
• •  sub-menu 'service', click on calibration, then OK

This calibration applies to optics downstream of the cell, if the problem persists then it is at the cell or upstream.

If the cell is the cause ...

To confirm if the cell is the cause, one may have to remove and clean it: this will be lesson #2
possible causes:

• •  internal stains or pollution (see prevention)
• •  internal scratches (abrasive samples...)
• •  external stains or pollution (see prevention)
• •  external scratches, stains and pollution

Internal pollution prevention

Internal pollution of cell glasses can often be prevented, delayed or reversed by simple measures you should know

• •  drop of surfactant (Palmolive) at rinsing
• •  light acid flow 10 min. 1 /month
• •  multiple rinsing with surfactant before attempting manual cell cleaning
• •  rinsing with solvants (rare)
• •  not using the unit? : make sure the cell remains wetted

A 60 micron filter protects recirculators connected to water network. uncloag it once / 2-3 years.
Tip : use the filter at the inlet side of the tubing as a plunger into beaker or water tank

Preventing pollution of the outside

special laser coatings are on the outside of cell windows. if stained or damaged: very difficult to get them back to work

• •  NEVER NEVER TOUCH the windows!
• •  Check that O'Rings are in place and secure tight
• •  never disassemble
• •  change from wet to dry mode very great care
• •  never use ultrasonic bath or cleaning machines