RS Korea — TESTO 6681 High-Humidity Temperature/Humidity Transmitter Installation for Concrete CO₂ Curing Research

RS Korea installed a TESTO 6681 environmental transmitter with a 6614 high-humidity probe as the final phase of an ongoing research project studying CO₂-cured concrete strength. Project background: The research institute is investigating how injecting CO₂ during concrete curing affects hardness, and had previously used RS Korea's FIX800 CO₂ detector to monitor gas levels inside the curing chamber. Condensation from the required temperature and humidity conditions initially caused equipment failures, which RS Korea resolved with a custom sampling system. Following that success, the institute built a larger custom chamber requiring a full replacement instrumentation set — CO₂ detector, data logger/controller, and temperature/humidity measurement — which RS Korea supplied and installed. Why a specialized humidity sensor was needed: Most commercially available humidity sensors use exposed capacitive elements that respond quickly and measure accurately, but are vulnerable to moisture damage in high-humidity environments (above roughly 80% RH). The TESTO 6681 transmitter with the 6614 probe addresses this with a heated humidity sensor that prevents condensation from forming directly on the sensing element — a feature not available on combined temperature/humidity sensors, which can lose temperature accuracy while their anti-condensation heating is active. Installation: The TESTO 6681 was configured with 4–20 mA output channels for temperature and humidity, mapped to the receiving data logger, and mounted inside the existing control box using its factory bracket, fitting the pre-cut enclosure opening. During commissioning, raising the chamber temperature to around 65°C caused ambient humidity to drop rather than rise as expected, since latent heat from the standing water in the chamber had not yet activated at that temperature — effectively drying the chamber like a hair dryer. RS Korea recommended maintaining the current temperature range while adding a separate water-boiling unit to generate humidity more directly, rather than relying on ambient evaporation. This project builds on RS Korea's existing CO₂ gas measurement capability, extending its instrumentation and control offering to include temperature, humidity, and (on request) pressure monitoring for safety, production, and R&D environments nationwide.