Case Study: Industrial Measurement
FIC UK Ltd., Penzance. This is a specialist company based in West Cornwall involved in the manufacture of instrumentation and process control equipment for the production of automotive glass (windscreens, car windows etc.)
This is a niche product area, with high capital value and low unit volumes. The equipment is distributed world wide which means that assemblies must be tolerant of significant heat variations. The cost of down time and geographical barriers mean that reliability is of prime importance.
The company had a design that was expensive to manufacture and had already been "stretched" to achieve its performance. Part of the overall cost was based on the labour required to align 6 adjustments on the board. In shipping it was possible for these adjustments to drift out of specification, requiring service or return to base.
FIC sought three quotations, one from a design facility with whom they had worked previously. Hawkshead was asked to quote based on the same basic data provided. In essence it was a measuring device where the temperature to be measured was at a potentially lethal voltage. This temperature had to be displayed on an electrically safe panel and powered from an isolated power supply. This is known as three port isolation.
After due consideration, Hawkshead returned a quotation that was the subject of detailed enquiry from FIC. The quote was less than 50% of either of the others, which were broadly similar. Hawkshead had already considered the "obvious" answer and its implications. The obvious route involved using a twin isolated supplies with circuitry controlled by a microprocessor. The processor would enable a temperature measurement to be turned into pulses which could be conveyed across an isolation device by means of light (opto-coupler). The receiving (safe side) would translate the pulse signal back into a voltage suitable for a temperature display.
Hawkshead proposed to use a single isolated power supply with a device known as an isolation amplifier. An isolation amplifier enables temperature measurement and power of its associated circuitry on the non-safe side. An isolation amplifier by definition boosts the signal and isolates the input from the output. All that remains is to match the output signal electrically to the display equipment.
The resultant quotation was less because it involved less work. There was no processor (and associated software) and the signal was never converted only ever scaled. Alignment was achieved with just two adjustments and about 250 were manufactured over a five year period. The returns and failure rate fell to less than 1% in that period.