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In this page you can find pictures and descriptions of typical equipment that has been used or calibrated in BCS approved laboratories.
Larger images are available by right clicking on individual pictures.
Fluke 540B Thermal Transfer Standard
This instrument is used to compare the RMS value of an AC signal with an equivalent DC signal. The comparison is conducted using a thermal element and there are various voltage ranges available, up to 1000 V.
These were standard equipment for many years but have now been largely superseded by multimeter-style devices that offer better accuracy and ease of use.
Cambridge "S-Class" standard resistors
Here is a set of four S Class resistors manufactured by the Cambridge Instrument Company.
General Radio GR900 Precision Fixed Attenuator
The GR900 series of coaxial components was of the highest quality, with extremely low VSWR (usually well under 1.01:1) and with excellent connector repeatability. They were of a hermaphrodite design, thus simplifying calibration set-ups considerably.
The GR900 is a 14 mm 50 Ω connector with an operating frequency range of DC to 8.5 GHz.
ESI Precision Resistance Measuring System
This comprehensive DC resistance measurement system comprises the following sub-assemblies:
Model 801 DC Generator Detector
Model 240C Kelvin Ratio Bridge
Model RS925C Decade Resistance Standard
The system can measure resistance values up to 100 MΩ. The power supply provides up to 600 V DC and the maximum detector sensitivity is 3 μV full scale.
Avometer Model 8
The Avometer was in continuous production for 85 years. The millionth Avometer was manufactured during the 1960s and production continued until the end of 2008. The link at the foot of this page contains an article written by John Hurll for Measurement and Control that provides a brief history of the Avometer.
Fluke 720A Kelvin Varley Divider
This classic 7-decade Kelvin Varley divider includes a built-in Wheatstone bridge for alignment purposes. It features linearity errors of fractions of a part per million. It has numerous applications, including calibration of other dividers, intercomparison of standard resistors and providing low level direct voltages.
Tinsley "Wilkins" 100 Ω standard resistor
The design for this type of resistor originated with F. J. Wilkins of the National Physical Laboratory.
Often simply known as the "Wilkins" resistor, the design features low temperature coefficient and time constant, making them suitable for AC applications, as well as DC.
This one belonged to the British Calibration Service and was used as part of their interlaboratory comparison activities, usually referred to as Measurement Audit.
General Radio Standard Inductors
General Radio (GR) manufactured a range of high quality reference standards and measuring equipment. A range of toroidal inductors was available; two examples are shown below.
An interesting and detailed history of the General Radio Company can be viewed or downloaded at the foot of this page.
GR History.pdfTheLastAvometer.pdfPage updated
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