Model D集成电子管放大器,当时为了制造石英棱镜,石英得从巴西运来,但是,由于石英是射频振荡器必要的元件,而射频振荡器是无线通信系统必须的(石英振荡器,比如目前电子电路中用的很多的晶振),所以战时,石英还很难搞到,不过由于美国大兵要吃维生素,所以政府出面解决了这个问题。
注:第一台计算机ENIAC就是用电子管做的。电子管目前也还在用,比如一些音频发烧友做的“胆机”。
回来再说Model D, 当时Model D面临着两个挑战。
一个是,设计合适的紫外光源。因为最初使用的是钨灯,而钨灯在可见光区还行,但紫外区,能量太弱,不适合使用。当时已经知道氢灯可以产生紫外辐射,但是,在1940年,还没有哪个厂家可以制造适合UV-vis使用的氢灯,为此,National Technical Laboratories(Bechman公司的前身)开始自己设计、制造氢灯,灯的问题终于解决了。
另一个是挑战是,没有合适的光电检测器可用于紫外区,当时的光电检测器只能检测350nm~1200nm的光,350nm以下的没有合适的,为此,RCA设计了个实验用的光电检测器,可以检测低到220nm的光,但是,这个新发明批量小,而且不稳定,没办法,最后,Model D还是使用了这种新检测器。
由于RCA的不合作,老Bechman和他的同事最终还是自己设计了可用于紫外区的光电检测器。并把使用这种检测器的UV-vis命名为 Beckman DU(如图1.1.4).
图1.5是Beckman公司当时对 Beckman DU做的广告
图1.1.5中的介绍文字如下:
September 25,1941 , NEWS EDITION
注:--------杂志名和发表日期
Features Many Unique and Far-Reaching Advancements
This precision instrument -the product of several years intensive development by the Beckman research staff -incorporates many inportant advancements in the design of spectrophotometric equipment,such as :
... the finest type of crystal quartz monochromotor which covers the full spectral range of interest in spectrophotometry -200 millimicrons in the ultraviolet to 2000 millimicrons in the infrared.
....precision optical parts completely protected from dust and fumes.
....extra long(100cm) easily-read wavelength Scale.
....direct readings in both % Transmission and Desity -simultaneously
....continuously adjustable Slit Machanism to fit every possible requirement.
....full scale readings with nomianl band widths 2 millimicrons or less over most of spectral range.
....stray light effects less than 1/10% over most of the spectral range.
注: 这个仪器的大小没有查到相关资料,不过一个线索是,extra long(100cm) easily-read wavelength Scale.在图1.1.3中,也有个说明是,length : Approximately four feet 。在对比下图1.1.2,有什么想法吗?
图1.1.6是1951年11月30日的一个广告,以下是图1.1.6的放大说明。
QUARTZ SPECTROPHOTOMETER, Beckman Photoelectric. A self-contained unit
with which a wide variety of research and control work can be conducted with convenience,speed and precision. Consisting of quartz monochromator with light source, holder for absorption cells, twin phototubes and built-in electronic meter for translating phototube currents into direct readings of percentage transmission and density. See Gary and Beck-man, Journal of the Optical Society of America, Vol. 31, No. 11., (Nov., 1941), p. 682.Wavelength scale approx. 100 cm long, readable and reproducible to 0.1 mmu in the ultraviolet and to 1.0 mmu in the infrared, with scale accuracy of 1 mmu. Built-in potentiometer and electronic amplifier makes possible direct readings in percpntage transmission and density. Switch position "0.1" provides a ten-fold expansion of the transmission scale for mre accurate readings on solutions below 10% transmission.
The new model No. 2400 is provided with a liquid-cooled, cast metal lamp housing which takes tungsten, hydrogen and mercury lamps mounted on self-aligning, interchangeable backplates. In addition, a resistor box assembly (not shown in illustration), with three-position switch, is attached to the phototube compartment for rapid and convenient selection of proper phototube load resistor to regulate the sensitivity for alternate use in transmission and flame photometry.
9101-A2. Quartz Beckman Photoelectric, Model DU (No 2400), range 320 to 1000 mmu, as above described, with volt tngsten lamp in liquid-cooled lamp housing with interchangeable backplate, one each ultraviolet-sensitive and caesium-oxide phototubes, resistor box assembly, matched set of four square fused Corex glass absorption cells for 10 mm liquid depth and 4-place holder. With dry cells for operating the meter but without 6-volt storage battery for operating the tungsten lamp and electronic tubes. ..... 1,250.00
9101-A2. Quartz Beckman Photoelectric, Model DU (No 2400), range 320 to 1000 mmu, as above described, with volt tngsten lamp in liquid-cooled lamp housing with interchangeable backplate, one each ultraviolet-sensitive and caesium-oxide phototubes, resistor box assembly, matched set of four square fused Corex glass absorption cells for 10 mm liquid depth and 4-place holder. With dry cells for operating the meter but without 6-volt storage battery for operating the tungsten lamp and electronic tubes. ..... 1,250.00
9101-B2. Ditto, Model DUV, range 220 to 1000 mmu, identical with above but with the addition of ultraviolet accessories consisting of one pasr of matched fused silica absorption cells for 10 mm liquid depth, hydrogen discharge lamp on interchangeable backplate, and power supply unit, 115 volts, 50/60 cycles, a .c . ... 1, 575.00
注: 上面的range 320 to 1000 mmu,应该是指波长,mmu全称是什么呢?
9101-A2的波长范围是320 to 1000 mmu, 这个应该是Beckman Model D以前的产品。
9101-B2的波长范围是 220 to 1000 mmu,这个应该Beckman DU后面的产品了。
Bechman DU被证明是分析仪器历史上最了不起的设计之一 , 它不仅是第一个触及紫外区的有着高精确度的仪器,而且把机一体化仪器概念介绍给了无数科学家。