Background information
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usbpt104.en r2
Because of the low signal levels, it is important to keep any cables away from electric
cables, motors, switchgear and other devices that may emit electrical noise. Using
screened cable, with the screen grounded at one end, may help to reduce
interference. When using long cables, it is necessary to check that the measuring
equipment is capable of handling the resistance of the cables. Most equipment can
cope with up to 100 per core.
The type of probe and cable should be chosen carefully to suit the application. The
main issues are the temperature range and exposure to fluids (corrosive or
conductive) or metals. Clearly, normal solder junctions on cables should not be used
at temperatures above about 170 °C.
Sensor manufacturers offer a wide range of sensors that comply with BS1904 class B
(DIN 43760). These sensors offer an accuracy of ±0.3 °C at 0 °C. For increased
accuracy, you can use BS1904 class A (±0.15 °C) or tenth-DIN sensors (±0.03 °C).
Companies like Isotech can provide standards with 0.001 °C accuracy. Please note
that these accuracy specifications relate to the SENSOR ONLY. It is necessary to add
on any error in the measuring system as well.
Related standards are IEC751 and JISC1604-1989. IEC751 also defines the colour
coding for PRT sensor cables: the one or two wires attached to one end of the sensor
are red, and the one or two wires at the other end are white.