The core of the thermal resistance induction in high and low temperature test chambers also utilizes the physical property that the resistance value of platinum metal changes with temperature. The core logic of the control system is a closed-loop feedback control: measurement → comparison → regulation → stability
Firstly, the thermal resistance sensor senses the current temperature inside the chamber and converts it into a resistance value. The measurement circuit then converts the resistance value into a temperature signal and transmits it to the controller of the test chamber. The controller compares this measured temperature with the target temperature set by the user and calculates the deviation value. Subsequently, the controller outputs instructions to the actuator (such as the heater, compressor, liquid nitrogen valve, etc.) based on the magnitude and direction of the deviation. If the measured temperature is lower than the target temperature, start the heater to heat up; otherwise, start the refrigeration system to cool down. Through such continuous measurement, comparison and adjustment, the temperature inside the box is eventually stabilized at the target temperature set by the user and the required accuracy is maintained.
Due to the fact that high and low temperature test chambers need to simulate extreme and rapidly changing temperature environments (such as cycles from -70°C to +150°C), the requirements for thermal resistance sensors are much higher than those for ordinary industrial temperature measurement.
Meanwhile, there is usually more than one sensor inside the high and low temperature test chamber.
The main control sensor is usually installed in the working space of the test chamber, close to the air outlet or at a representative position. It is the core of temperature control. The controller decides on heating or cooling based on its readings to ensure that the temperature in the working area meets the requirements of the test program.
The monitoring sensors may be installed at other positions inside the box to verify with the main control sensors, thereby enhancing the reliability of the system.
Over-temperature protection is independent of the main control system. When the main control system fails and the temperature exceeds the safety upper limit (or lower limit), the monitoring sensor will trigger an independent over-temperature protection circuit, immediately cutting off the heating (or cooling) power supply to protect the test samples and equipment safety. This is a crucial safety function.
Lab thermal resistance sensor is a precision component that integrates high-precision measurement, robust packaging, and system safety monitoring. It serves as the foundation and "sensory organ" for the entire test chamber to achieve precise and reliable temperature field control.
High and Low Temperature Test Standard of PC Plastic Material
1. High temperature test
After being placed at 80±2℃ for 4 hours and at normal temperature for 2 hours, the dimensions, insulation resistance, voltage resistance, key function, and loop resistance meet the normal requirements, and there are no abnormal phenomena such as deformation, warping, and degumming in appearance. The key convex point collapses at high temperature and the press force becomes smaller without assessment.
2. Low temperature test
After being placed at -30±2℃ for 4 hours and at normal temperature for 2 hours, the dimensions, insulation resistance, voltage resistance, key function, and loop resistance meet normal requirements, and there are no abnormal phenomena such as deformation, warping, and degumming in appearance.
3. Temperature cycle test
Put in 70±2℃ environment for 30 minutes, take out at room temperature for 5 minutes; Leave in -20±2℃ environment for 30 minutes, remove and leave at room temperature for 5 minutes. After such 5 cycles, the dimensions, insulation resistance, voltage resistance, key function, circuit resistance meet the normal requirements, and the appearance of no deformation, warping, degumming and other abnormal phenomena. The key convex point collapses at high temperature and the press force becomes smaller without assessment.
4. Heat resistance
After being placed in an environment with a temperature of 40±2℃ and a relative humidity of 93±2%rh for 48 hours, the dimensions, insulation resistance, voltage resistance, key function, and loop resistance meet normal requirements, and the appearance is not deformed, warped, or degumped. The key convex point collapses at high temperature and the press force becomes smaller without assessment.
National standard value for plastic testing:
Gb1033-86 Plastic density and relative density test method
Gbl636-79 Test method for apparent density of moulding plastics
GB/ T7155.1-87 Thermoplastic pipe and pipe fittings density determination part: polyethylene pipe and pipe fittings reference density determination
GB/ T7155.2-87 Thermoplastic pipes and fittings -- Determination of density -- Part L: Determination of density of polypropylene pipes and fittings
GB/T1039-92 General rules for testing mechanical properties of plastics
GB/ T14234-93 Surface roughness of plastic parts
Gb8807-88 plastic mirror gloss test method
Test method for tensile properties of GBL3022-9L plastic film
GB/ TL040-92 Test method for tensile properties of plastics
Test method for tensile properties of GB/ T8804.1-88 thermoplastic pipes polyvinyl chloride pipes
GB/ T8804.2-88 Test methods for tensile properties of thermoplastic pipes Polyethylene pipes
Hg2-163-65 plastic low temperature elongation test method
GB/ T5471-85 Method for preparing thermosetting molding specimens
HG/ T2-1122-77 thermoplastic sample preparation method
GB/ T9352-88 thermoplastic compression sample preparation
www.oven.cc
labcompanion.cn Lab Companion Chinalabcompanion.com.cn Lab Companion Chinalab-companion.com Lab Companion labcompanion.com.hk Lab Companion Hong Konglabcompanion.hk Lab Companion Hong Konglabcompanion.de Lab Companion Germany labcompanion.it Lab Companion Italy labcompanion.es Lab Companion Spain labcompanion.com.mx Lab Companion Mexico labcompanion.uk Lab Companion United Kingdomlabcompanion.ru Lab Companion Russia labcompanion.jp Lab Companion Japan labcompanion.in Lab Companion India labcompanion.fr Lab Companion Francelabcompanion.kr Lab Companion Korea
Get A Quote
IPv6 network supported