Sensors have been with us ever since the days when Watt invented the flyball governor for steam engine speed regulation. While we are seeing an increase in optical encoded outputs suitable for optical-fibre cable use, most sensors we encounter today use electrical signals to transmit their output back to the controlling device. With the increase in microprocessor-controlled signal processing the signal levels in the wiring harnesses have generally dropped to TTL/MOS levels, that is, voltages under 5 volts and with correspondingly low currents.

 

Unfortunately for the reliability of equipment whose operation is controlled by sensors, reliability in connectors used at these voltage and power levels has lagged behind the demands placed upon them. The consequences are, for example, that it is estimated that 10% of all automobiles stalled on the roadside are suffering from an electrical connector failure of some sort.

 

The same conditions exist in many other areas, be it untimely landing-gear retractions caused by "squat switch" failure to unnecessary rejections of IC's during the final acceptance tests caused by improperly functioning test fixture connectors.

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Where "sensor failures" occur, the loss of time and loss of product can be expensive. The cost of replacing perfectly good sensors because of the malfunction of a connector (whose cost is generally only a fraction of the cost of the sensor itself) can really hit a service group in the pocketbook. Normally, reimbursement of the service group for labor and parts costs are dependant upon testing by the manufacturer to verify that the assembly is actually at fault. The problem is that a simple disconnect and reconnect cycle will usually clear up the connector problem (for a short time anyway) and thus the faulty connector may perform flawlessly under the manufacturer's testing conditions. Not only is the customer annoyed by the original down time, but the service group is out of pocket. Another problem is the potential for loss of good relations between the dealer and customer, and between the manufacturer and dealer.

 

Often the long term duty cycle of the equipment can increase the problem. For example, in the agricultural implement field, the situation can be aggravated by the fact that the equipment is usually laid up for the larger part of the year and then is called upon to function perfectly during several weeks of intensive use.

 

It is not unusual for farmers to run their combines on a multiple-shift basis to bring in the crop as soon as the grain ripens. Any serious downtime can increase the potential for a major financial loss to the farmer, who may also be concerned with adverse weather conditions.