Advancements in electronics, especially in digital electronics and communications, have resulted in wide availability and use of mobile instrumentation. Mobile instruments are used in a variety of industrial and business applications. For example, utility companies use data entry terminals to enter utility data, such as readings from gas and electrical meters at points of use. As another example, transportation and wholesale services use handheld terminals to enter data related to services they provide, such as delivery address and customer name and signature.
Another area where mobile instruments and devices are used is industrial and technical fields. Many technical mobile instruments include a sensor of some sort to measure some physical quantity such as voltage, current, pressure, temperature, and humidity. Sensors may include circuits that are embedded within the mobile instrument, such as an ammeter used to measure current and voltage. Other sensors comprise independent devices coupled with the mobile instrument, such as thermistors used to measure temperature.
The mobile nature of such instruments often requires particular ruggedness to cope with various environmental factors, such as impact, abrasion, humidity, and extremes of hot and cold temperatures. For example, an industrial measurement instrument may fall on hard surfaces from a distance of a few inches to a few feet during normal operation. Accordingly, various ruggedized instruments and instrument casings have been devised to cope with the extra wear and tear in the field. Some of the above-noted industrial instruments that have internal sensor devices include probes that extend out from the industrial instrument to make measurements. For example, an ammeter that has current and voltage sensors implemented as internal circuits for measuring current and voltage may include probes that extend outwardly from the ammeter. In such instruments, the sensor device is protected because it is encased within the industrial measurement instrument rather than within the probe. In other industrial measurement instruments, however, the nature of the measurement is such that the sensor device needs to be located outside the confines of the industrial measurement instrument. For example, temperature and humidity sensors need to be in direct contact with air or other gasses, the temperature or humidity of which is being measured. In such instruments, the sensor device often is mounted in a probe and, thus, is particularly vulnerable because it is not encased within the body of the industrial measurement instrument. Such sensors require additional protection against physical impact and other environmental hazards.