Measuring Current: Innovations in Electronic Meters, 1948-1970

Swail Multimeter, CSTM artifact no. 1985.0825.001

Multimeter developed by Swail, c.1948

Throughout his career, James C. Swail sought to build devices that people who were blind or partially sighted could use to gain the experience and technical expertise needed to become employed within the fields of science and technology.[1] One of the first assistive devices Swail began working on when he joined the NRC was accessible electronic meters intended to test and measure current and resistance from a variety of electrical devices. He completed his first prototype of such a device in 1948, describing it as “a vacuum-tube voltmeter, which used a mechanical chopper, amplifier and headset as its auditory detector.”[2]

Pictured here, the multimeter consists of grey-painted metal and shaped like a cube measuring twenty centimeters by twenty centimeters by twenty centimeters. A small, round black plastic dial with a slim metal pointer attached rests at the center of the device, over top a clear, sloping plastic plate. This pointer – made of a long bent nail – projects out and down toward a series of raised markings or dots indented onto the plastic plate. The dots are arranged in a semi-circle around the knob and pointer, representing a calibrated linear scale of voltage levels that are divided into ten main divisions (indicated by double dots) and subsequent subdivisions (indicated by single dots).  This scale corresponds to different settings that can be adjusted by turning seven black knobs of varying sizes, positioned at the front lower half of the device. The two larger knobs, positioned side by side at the bottom center of the device, controlled range and voltage or resistance. An operator could plug in earphones in a jack on the bottom right-hand corner. Through the earphones, an operator could hear the indicated voltage level being read by the machine. Alternatively, they could connect a phototube for measuring light intensity through another jack on the bottom left-hand corner.[3]

Swail Ammeter, CSTM artifact no. 1985.0826.001

Swail Ammeter, c.1970

Swail’s approach to construction shifted in 1964 – rather than build meters from scratch, he began modifying existing devices.  One example of this new design is pictured here – an ammeter first manufactured by the company Bach-Simpson c.1970. This device is similarly made of grey-painted metal, but is rectangular in shape with rounded edges. Two round black dials with pointers are positioned side by side on a metallic metal plate at the front of the device. Like the first prototype, each dial is designed to point to a series of dots indented in the metal plate, representing a calibrated linear scale of voltage levels that are divided into ten main divisions and subsequent subdivisions.  This scale corresponds to different settings that can be adjusted by turning black knobs at the back and top of the machine. The knob at the top, intended to adjust voltage or resistance settings, is placed next to a white and black visual display, encased in a small black plastic frame. A round, metal-plated speaker is placed at the left-hand side of the apparatus, through which an operator can hear the voltage being read by the meter. Alternatively, a jack for plugging in earphones is placed at the back of the device, below a pair of matching vents.[4]    

 



[1] Euclid Herie, Journey to Independence: Blindness – The Canadian Story (Toronto: The Dundurn Group, 2005), 118.

[2] James Swail, “Electronics for the Blind,” Report of the National Research Council of Canada, Ottawa, ON, Canada (June 1962), 3.

[3] James C. Swail, “Radio Multimeter for Sightless Operators,” Report no. ERB-160, Laboratories of the National Research Council of Canada, Radio and Electrical Engineering Division, Ottawa, ON, Canada (May 1948); Swail Braille Multimeter, artifact no. 1985.0825.001, Collections Supplementary Report, Canadian Science and Technology Museum, Ottawa, ON, Canada. http://techno-science.ca/en/collection-research/collection-item.php?id=1985.0825.001

[4] Swail Braille Ammeter, artifact no. 1985.0826.001, Collections Supplementary Report, Canadian Science and Technology Museum, Ottawa, ON, Canada.  http://techno-science.ca/en/collection-research/collection-item.php?id=1985.0826.001

 

Measuring Current: Innovations in Electronic Meters, 1948-1970