What effect do environmental conditions have on the measurement accuracy of the electric contact pressure gauge?

Temperature fluctuation is an important environmental factor affecting measurement accuracy, especially in the application of electric contact pressure gauges. The core sensitive element of the electric contact pressure gauge is the spring tube, and there is a close relationship between its elastic modulus and temperature. When the ambient temperature deviates from the standard operating conditions (usually set to 20°C), the stiffness of the spring tube will change, resulting in a deviation in the conversion coefficient between deformation and pressure. In a high-temperature environment, such as next to a steelmaking furnace, the spring tube material may creep, and its deformation recovery ability will significantly decrease after long-term operation, which will cause hysteresis errors. This error may account for more than 20% of the total error at the lower limit of the pressure measurement range (such as 0-0.6MPa). Low temperature environments also pose a threat to measurement accuracy. When the temperature drops below -20°C, the solidification of grease will cause the transmission mechanism to jam, the response time of the pointer will be prolonged, and the dynamic error will increase significantly.

The presence of humidity and corrosive media also poses a serious threat to electric contact pressure gauges. A high humidity environment will accelerate the oxidation process of the contacts, resulting in increased contact resistance. In the case of low pressure measurement (such as 0-0.1MPa), this oxide layer may introduce an additional error of about 0.2%FS. If there are corrosive gases (such as chlorine, sulfur dioxide) in the environment, the case seals and spring tubes may be corroded, causing medium leakage or pressure transmission distortion. For example, in the chlor-alkali industry, ordinary stainless steel spring tubes can only maintain a service life of about 6 months in chlorine-containing media, while instruments using Hastelloy C-276 can extend their service life to more than 5 years.

Vibration is a common source of interference in industrial sites, and its impact on electric contact pressure gauges is often hidden. When the vibration frequency is close to the natural frequency of the instrument, resonance may be induced, causing the pointer to swing more than 1% of the range. This vibration not only affects the stability of the reading, but also accelerates fatigue damage to mechanical components. In centrifugal compressor units, if the vibration acceleration exceeds 5g, the repeatability error of the instrument may deteriorate from 0.5%FS to 2%FS. Long-term vibration environment may also cause poor contact of contacts, thereby causing false alarms.

Electromagnetic interference poses a severe challenge to the electrical performance of electric contact pressure gauges. In strong electromagnetic field environments such as frequency converters and high-voltage cables, millisecond-level jitter may occur when the contacts are closed, resulting in signal distortion. If effective shielding measures are not taken, surge current on the power line may enter the instrument circuit through capacitive coupling and damage precision components. For example, in wind farms, the failure rate of instruments using ordinary cables can be as high as 30% after being struck by lightning, while the failure rate of instruments using twisted-pair shielded cables can be reduced to less than 5%.

The impact of air pressure changes on sealing performance should not be ignored. In plateau areas (such as the Qinghai-Tibet Plateau), atmospheric pressure is only 60% of sea level pressure. If the instrument seal is not designed properly, it may cause internal pressure imbalance, which in turn changes the preload force of the spring tube. This change is particularly significant in low-pressure measurements and may cause measurement deviations of more than 5% FS. In addition, sudden changes in air pressure may also destroy the elasticity of the sealing rubber ring and cause leakage.

Lighting conditions can also affect the use of instruments in some special scenarios. In strong outdoor light, ordinary dials may be difficult to read due to reflections, and operators may have visual errors of up to 1%FS in order to obtain accurate readings. To solve this problem, meters with anti-reflective coatings or LCD screens can effectively improve the accuracy and readability of readings.