Operating Steps are numbered and the reasons they are performed are listed below each one.

1.  Turn on with Left hand knob.

The left hand knob also serves as the instrument's main power switch.  Sometimes it may be necessary to wiggle or gently pull this knob.

2.  Wait at least ten minutes for warm up.

The light source will not operate consistently without an adequate warm up nor will the instrument correctly zero unless the lamp is warm.

3.  Locate the %Transmittance scale on the meter.

Preliminary setup is done in the %Transmittance mode.  There are two scales depending on the type of measurement needed.

4.  Set the desired wavelength with the knob located on top of the unit.

5.   With the cuvette chamber empty, set zero %T using the left hand knob.

A small door closes and blocks out all light from the source.    There is now no transmission of any light and therefore  Transmission = 0

6.  Insert an empty cuvette and set the 100%T using the right hand knob.

Placing the tube in the chamber will open the door and allow light to pass.  There is now a maximum transmission of light.  Transmission = 100

7.  If instructed to use it, locate the absorbence scale.

Depending on the analysis, either absorption or transmission may be used.

8.  Insert the sample and take your reading.       
 
  
Special Instructions: 
     
1.  If a cuvette breaks inside the unit, report the accident to your instructor immediately.  Leaving liquids inside the machine will result in corrosion.

2.  Every time you change the wavelength, you must reset the zero and the blank.

3.  For best results use clean cuvettes and do not write on them.  You may need to clean the cuvettes with a lint-free wipe.

4.  When using the analog instrument, look directly at the scale to avoid parallax error.  Use the mirror behind the needle to align your vision.

5.  Turning any of the instrument's knobs clockwise will increase a value.      

USING THE DIGITAL SPEC 20D