Laser Tracker Atmospheric Error Fundamentals and Sensor Hardware Selection
Atmospheric refraction errors in laser tracker metrology demand precise temperature, pressure, and humidity compensation to maintain sub-millimeter precision.
Pt100 RTD Sensor
Meaning
Resistance-based temperature detection devices exploit the predictable change in electrical resistance of platinum as a function of thermal variation. In industrial process control and high-performance electronic enclosures, the Pt100 RTD sensor provides a highly stable and linear measurement with a nominal resistance of 100 ohms at zero degrees Celsius. This instrument operates by passing a small, constant excitation current through the platinum element and measuring the resulting voltage drop.
The stability of platinum ensures that the sensor maintains high precision over a broad operating temperature range.
Wiring Configuration
System designers must select multi-wire connections to balance cost and accuracy. A two-wire setup is susceptible to lead-wire resistance errors, which can distort the temperature calculation. Implementing a three-wire or four-wire configuration allows the measurement circuit to compensate for lead-wire resistance.
This compensation is necessary when the sensor is located far from the digitization circuitry.
Excitation Limit
Passing too much current through the platinum element causes self-heating, which raises the sensor temperature above the ambient level. Designers limit the excitation current to avoid this measurement error.
Thermal Assembly
Proper mechanical integration requires placing the sensor in direct thermal contact with the target object or fluid. Thermal paste or conductive mounting brackets are used to minimize the thermal resistance of the interface. This contact ensures rapid response times to sudden temperature changes, allowing the controller to take corrective action before overheating occurs.