A Variable Reference Beam Attenuator for Infrared Spectrophotometers We have noted that undereraduates leamine ta use an infrared soectro~hotometer invnrinhly hnvedifficulty balaking rhesanlplekd rcfrrrncr h ~ n m s i n m d iulnhtnin r nnnrce1,ral,lespccrrunl.'l'hii ikrsprcinllptrus whpn prrpnrmg KBr pelletsand uhen wing pitted ajdium rhloridr plates. A.though most lnsrruments hnvc nn ndlustmrnt for the sample beam, in many cases balance can only be obtained by an adjustment of the reference beam. T o thisend, we haveoecasionally used screens of various mesh size which is a cumbersome trial and error technique. Recently, it occurred to usto use an irisdiaphragm to adjust the reference beam. We mounted a purchased diaphragm an s brass plate fitted for either of the two different student instruments we use (Perkin-Elmer Models 137 and 710A). A line drawine u,ith ywrlftmtions IS shown. The fin1three atttnuarwi were made l l s i n ~a mrrhat>irul clamp 18, h d d the dmphragm I*,I he plate, howcwr; ur hnvr aincr uwd ~ X I X Y10 imply glue the parts together Although reducing the reference beam reduces sensitivity, we were able to obtain excellent spectra an fast scan with the diaphragm closed to its minimum opening of 1mm. The diaphragms were purchased from Edmund Scientific Company (Barrinaon, N.J.) for $9 each which was the only materials cost. We have now fitted these to all of our undergraduate infrared instruments. University of Missouri-St. St. Louis, MO 63121
Louis
David L. Garin Ted Windsar
Volume 57, Number 6,June 1980 1 463
