Zhanlin Instrument Science Popularization

Light intensity ≠ Blackboard temperature signal

disassembleQ-SUNControl circuit of xenon lightbox

In the assessment of material weather resistance, some engineers who are new to aging testing have these questions:Is the light intensity of the xenon lamp aging chamber related to the signal data of the blackboard sensor (blackboard thermometer)

Zhan Lin Instrument first announced its conclusion: No.

At Q-SUNXenon lamp aging test chamberIn China, the light intensity and blackboard temperature (BPT/BST) are controlled by two independent measurement and control circuits - the former is closed-loop controlled by an irradiance sensor, and the latter is closed-loop controlled by a blackboard thermometer to regulate the thermal environment.

It is more scientific to separate the control of "light" and "temperature" in accelerated aging testing. The photochemical reactions of materials are mainly driven by spectral composition and irradiation dose, while thermal oxidation and thermal aging depend on temperature levels and thermal history; Only by setting the two independently and implementing closed-loop control can we more clearly identify the failure mechanism and avoid judgment bias caused by variable coupling.

At the same time, industry and national standards usually specify the type/set value of light intensity control points and blackboard temperature simultaneously. Only by controlling them separately according to the standards can the test results be comparable and traceable with historical and cross laboratory data.

Of course, in addition to the blackboard temperature, synchronously controlling the cabin air temperature (CAT) and relative humidity (RH), and adding water spray/condensation programs as needed, can help stabilize the "light heat humidity" three elements within the target window, improving the robustness and reproducibility of the experimental process.

Firstly, light intensity=irradiance closed loop (not blackboard signal)

Q-SUN adopts dedicated technologyIrradiance sensorReal time sampling of light intensity in the target wavelength band (such as 340 nm, 420 nm, or TUV 300-400 nm), and automatic adjustment of lamp power to stabilize the light intensity at the set value (such as 0.35 W/m ²)/ nm@340 Nm, etc.).

That is to say, the "light intensity value" you set on the touch interface is maintained by the optical sensor in a closed loop; Blackboard thermometers do not participate in the light intensity closed-loop.

Secondly, blackboard temperature=representative value of surface temperature (independent temperature control circuit)

The blackboard thermometer reflects the trend of the sample's surface temperature tending towards the highest under strong light, and the device adjusts the thermal balance accordingly to maintain the BPT/BSTsetting So, blackboard thermometers are used for temperature control, not light intensity control; It is two different measuring devices from the irradiance sensor.

In terms of definition and principles, BPT/BPBelonging to an uninsulated blackboard: the back is not insulated and easily exchanges heat with the air inside the cabin; The temperature rises and falls quickly. And BST/IBPBelonging to the insulation blackboard/black standard: adding insulation layer on the back for better insulation; Closer to the highest temperature trend on the sample surface.

Under the same conditions, BST readings are usually higher than BPT (commonly seen in engineering as several ℃ to over ten ℃ higher, affected by wind speed, loading capacity, light intensity, and cabin temperature). BPT is more sensitive and responsive to airflow/heat dissipation; BST has a large thermal inertia and a higher peak value.

In common international standards,ASTMBPT is commonly used for routes, while BST/IBP is commonly used for ISO routes; So the two cannot be directly compared or simply converted. However, generally speaking, samples with thin sheets/high thermal conductivity/metal substrates and easy heat dissipation on the back are preferred for BPT. Samples with thick/insulated/3D structures and difficult to dissipate heat on the back can be prioritized for BST/IBP.

1. Light intensity closed-loop

The Q-SUN xenon lamp test chamber samples the light intensity in real-time at selected control points (such as 340 nm, 420 nm, or TUV 300-400 nm) using an irradiance sensor, and automatically adjusts the lamp power to stabilize the irradiance at the set value. This can eliminate drift caused by factors such as lamp decay and filter changes, ensuring consistent and comparable light doses between different batches and experiments.

2. Temperature closed loop

The Q-SUN xenon lamp test chamber uses the reading of the blackboard thermometer (BPT or BST) as feedback to dynamically adjust the thermal balance to maintain the target blackboard temperature; For some methods or cycles, the cabin air temperature (CAT) can also be controlled simultaneously to further stabilize the overall thermal field beyond the blackboard temperature, making the sample under more reproducible experimental conditions.

3. Humidity and moisture

According to standard or method requirements, relative humidity (RH) control can be enabled, and water programs such as spraying and condensation can be added to create a more outdoor "light heat moisture water" coupling environment in the laboratory. This helps to reveal the failure modes that materials may exhibit in real climates.

4. Data traceability

The Q-SUN xenon lamp test chamber system can record and export key environmental parameters (such as light intensity, blackboard temperature, CAT, RH, and time/cycle program) online, facilitating quality review, method review, and cross laboratory comparison; It also provides a traceable data foundation for anomaly analysis and long-term trend assessment.

Q-SUN series xenon lamp test chamber

·Full spectrum solar simulation:Covering UV visible near-infrared, close to natural sunlight distribution.

·Irradiance closed loop:340/420/TUV control points are optional, with automatic steady-state control to reduce drift caused by lamp decay and filter changes.

·Dual Blackboard Options:Support BPT uninsulated blackboards and BST/IBP insulated blackboards, complying with different standard routes such as ASTM/ISO.

·Multi factor synchronization:It can synchronously control the blackboard temperature, cabin air temperature (CAT), and relative humidity (RH), and support water spraying/condensation and other moisture programs.

·Traceability and Compliance:Real time recording of key parameters facilitates quality system audits and cross laboratory comparisons.

·Multi model coverage:Desktop and floor standing models are available, meeting different scenarios from R&D validation, small batch formula screening to mass production quality control.