Expert in Optical & Thermal Measurement Solutions
Due to the availability of ASTM C518-21, we’ve updated our SAC-SINGLAS accreditation schedule to ASTM C518-21. New test reports will be issued based on ASTM C518-21 accordingly.
Please also refer to the updated sample test report.
The Universal Thermal Climate Index (UTCI) is a measure of the thermal environment that influences human comfort and health. The HD32.3TC thermal comfort data logger for PMV/PPD/WBGT/turbulence measurement can be configured to measure UTCI, without hardware changes.
Shown below are some photos of HD32.3TC in the UTCI measurement mode.
We’ve just released our Q1/2023 OTM Insights newsletter, with the main article “Glass color, color difference & color rendering“.
Please click the image below to read the newsletter. For the past issues, please proceed to our branding & publications page.
We are a Singapore-based third-party test laboratory, providing lab test services of material optical & thermal properties. We use Xiatech TC3000E transient hotwire thermal conductivity meter, with the following key information.
The instrument is equipped with two probes, a thin film probe, and a needle probe.
The thin film probe is mainly for flat plate solid samples:
The thin film probe is mainly for bulk gel or soft soil samples:
UVC disinfection is used in HVAC systems to eliminate germs and viruses, particularly in the current COVID-19 situation. UVC irradiance measurement is required for UVC radiation level control.
Shown below is a handheld data logger for UVC irradiance measurement, with the following components:
At the customer’s request, an ISO 17025 calibration certificate can be provided at an additional cost.
Thermal conductivity, thermal resistance, and thermal transmittance are the 3 commonly used properties related to material or system thermal insulation performance. The 3 properties and their differences are explained below.
Thermal conductivity represents the ability of a material to conduct heat.
Thermal conductivity is also called K-value and its unit is W/(m⋅K). The smaller the thermal conductivity, the better the thermal insulation performance.
Listed in the table below are the typical thermal conductivity ranges of selected building material types.
| Building material type | Typical thermal conductivity range |
|---|---|
| Insulation material (e.g. polyurethane/polystyrene foam, mineral wool) | 0.02 – 0.04 W/(m⋅K) |
| Wood, plywood, and gypsum board | 0.1 – 0.5 W/(m⋅K) |
| Coating (e.g. paint), plastics, and rubber | 0.1 – 0.5 W/(m⋅K) |
| Glass | 1 W/(m⋅K) |
| Concrete (light weight or heavy weight), brick, and tile | 0.5 – 2.5 W/(m⋅K) |
| Metal (e.g. stainless steel or aluminum) | 15 – 200 W/(m⋅K) |
Thermal conductivity is typically for homogeneous materials. For inhomogeneous materials (e.g. concretes or composite panels), their average thermal conductivity is referred to as the apparent thermal conductivity.
Thermal resistance represents the ability of a material layer to resist heat transmission. Thermal resistance is calculated as:
Thermal resistance is also called R-value and its unit is (m2K)/W. The greater the thermal resistance, the better the thermal insulation performance.
Thermal resistance is always in terms of one or multiple material layers with fixed thicknesses:
Thermal transmittance represents the ability of a wall, roof or fenestration system to transmit heat. Thermal transmittance is calculated as:
Thermal transmittance is also called U-value and its unit is W/(m2K). The smaller the thermal transmittance, the better the thermal insulation performance.
Thermal transmittance is always in terms of a complete wall/roof/fenestration system and air-to-air thermal transmission.
OTM provides two online thermal transmittance (U-value) calculators:
The discussions above follow typical engineering practices. In the academic context, the practices could be different.
If we use double glazing unit (DGU) glasses as an example, the engineering practice is to use its thermal transmittance (U-value), instead of the other two, for performance evaluations, though in the academic context it is still correct to calculate the apparent thermal conductivity and thermal resistance of a DGU glass.
After testing, a test sample is retained by the lab for a certain period. The following sample retention periods are implemented at OTM:
| Sample type | Size range | Retention period |
|---|---|---|
| Small samples | Smaller than 10 cm × 10 cm × 3 cm | 3 years |
| Large samples | Larger than 10 cm × 10 cm × 3 cm Smaller than 30 cm × 30 cm × 5 cm | 1 year |
| Oversize samples | Larger than 30 cm × 30 cm × 5 cm | 3 months |
At the end of the retention period, the sample will be disposed of by the lab. The lab may further retain some samples for internal quality control purposes.
Upon the customer’s request (indicated in the test request form or in writing), a test sample can be returned to the customer.
Shown below is a wind speed and wind direction measurement system, with the following components:
For this system, OTM also supplied a 2-meter-long stainless steel pole for mounting and wired/configured all instruments before delivery. The last step mechanical mounting was done by the end user. A USB dongle type base unit (HD35APD) was also included for manual downloading of monitoring data in a scheduled interval.
We are able to measure glass emissivity according to EN 12898:2019, with the PerkinElmer Spectrum Two FTIR spectrometer and PIKE 10Spec 10-degree specular reflection accessory.
The total normal emissivity (εn) result is reported. The corrected emissivity (ε) is calculated and presented in the appendix. For glass U-value calculation, the corrected emissivity should be used.
As defined in ISO 9050 or EN 410, the UV transmittance of glass is calculated with the equation below:
In the equation above:
The wavelength range of interest is 300 nm – 380 nm. The term SλΔλ is the weights used in the weighted average of the spectral transmittance. The standard values of SλΔλ are plotted in the figure below.
The peak of the UV radiation distribution is at 375 nm. Glasses with high spectral transmittance near 375 nm are with high UV transmittance.
There are some small differences between the ISO 9050 and EN 410 UV distributions. The UV transmittances calculated according to the two standards could be slightly different.