Bench Instrument Research Articles

Evaluation of a dual-function pH and PCO2 in vivo sensor.

A newly developed, dual-function pH and PCO2 sensor was evaluated in this study. The sensors were placed in the femoral arteries of dogs anesthetized with sodium pentobarbital. Comparisons were made between systemic arterial pH and PCO2 measured using the sensor and those measured from blood samples drawn at 15-min intervals over a 7-h period using a bench instrument. The mean pH of the bench instrument measurements was 7.43. The mean difference of the sensor measurements from the bench instrument measurements for 207 comparisons was 0.0003 pH +/- 0.061 SD. The mean PCO2 of the bench instrument measurements was 40 mmHg. The mean difference of the sensor measurements from those of the bench instrument for 212 comparisons was -1.43 mmHg +/- 5.17 SD. The sensors performed equally well in the presence of metabolic or respiratory acidosis and alkalosis. The dual-function sensors evaluated in this study are useful for trend monitoring of pH and PCO2 over at least a 7-h period without recalibration. With improvement in the consistency of sensor construction, these sensors will be reliable in vivo sensing devices for blood pH and PCO2 and thus valuable research and clinical instruments.

Instrumentation: Insight into interfacing: Thorough and unambiguous understanding of interface systems demands sound design concepts and a precise descriptive language

An interface system definition, one optimized for the interconnection of programmable bench instruments, must contain many vital communication capabilities if it is to interconnect independently manufactured products at reasonable costs. It must also maintain a high level of compatibility, and a high degree of flexibility. The purpose of this article is to discuss not only the definition of the interface itself, but also the manner in which it is organized and the method by which it satisfies the user's needs.

Paper 20: New Optical Method of Assessing Surface Quality

A new method of assessing surface quality is described in which the light scattered from the surface is scanned by the edges of a chopper disc. The electrical output from the photocell is differentiated twice to give a signal which is a measure of the maximum rate at which the intensity of the reflected light falls off. It allows a simple, cheap, and robust instrument to be made which is insensitive to ambient illumination and can be used as a surface comparator either ‘on-line’ or as a bench instrument.

The Miniature Microscope in Forensic Science

A microscope is described which measures only 4 x 2 1 2 x 2 inches and weighs only 18 ounces, and yet which claims to be capable of every operation within the range of the largest conventional bench instrument, and of several other operations of which no other microscope is capable. Carrying standard optics, including an oil immersion objective, with a self-contained electric illuminator it provides magnifications up to 1,500X. It is capable of transmitted, incident, dark ground and phase contrast illumination, examination of large opaque surfaces and particles in volumes of fluid, polarising, comparison, measurement and counting, photo and cine microscopy, all with the instrument held in the hand, if necessary in the dark and under uncomfortable conditions, and even in the presence of vibration and movement, yet with an image equal in magnification and definition to any conventional instrument. It is designed for both scene-of-crime examinations and critical laboratory bench work.