The Extech RHT30 is a compact USB humidity and temperature datalogger designed to be plugged directly into a PC for setup and data retrieval. The unit integrates an NTC thermistor for temperature measurement and a capacitive humidity sensor in a housing roughly 4.3 x 1.6 x 0.75 inches, weighing about 1 ounce, with a standard USB connector that doubles as the data interface to the host computer.

Dataloggers in this category are deployed where a continuous record of ambient conditions matters more than a real-time readout — environmental monitoring of storage areas, shipping and logistics applications, building science surveys, laboratory and equipment rooms, and any setting where humidity and temperature must be documented over hours, days, or weeks. The RHT30 supports these applications with a programmable sampling interval from 30 seconds to 2 hours, a start delay, and configurable high/low alarms with an alarm delay.

ValueTronics International operates from a 20,000 square foot secure warehouse at 1675 Cambridge Drive in Elgin, Illinois, where every datalogger and instrument we sell is received, inspected, and prepared for shipment by our own team. We have built our reputation on direct hands-on handling of the products we offer — not drop-shipping through third parties — so customers ordering an RHT30 work with people who can answer questions about the unit and stand behind the condition we describe.

Brand Heritage

Extech Instruments is part of FLIR Systems, which placed the Extech brand within its broader portfolio of test and measurement and thermal imaging products. FLIR Systems was subsequently acquired by Teledyne Technologies in 2021, bringing the Extech product line under the Teledyne FLIR umbrella while preserving the Extech brand identity on dataloggers, environmental meters, and related instruments.

Compare Other Models in This Series

The RHT30 and RHT35 share the same compact USB-connected form factor, the same 5-digit LCD with battery life indicator, the same red and green LED status scheme, and the same user-programmable settings for sample rate, start delay, alarm delay, high/low alarm range, language selection, and password-protected security login. Both units use a built-in NTC thermistor for temperature and a capacitive humidity sensor, both ship with two CR2032 batteries, a USB cover that doubles as a stand, a wall mounting screw, and a built-in hanger, and both generate PDF or Excel output on PC connection.

The two models differ in one core capability: the RHT35 adds a built-in MEMS barometric pressure sensor, recording pressure alongside humidity and temperature. This third channel changes both the measurement scope and the way memory is allocated between channels, which in turn affects how each model is best matched to specific applications.

Each new model in this family is listed on its own dedicated product page with condition-matched pricing and availability. Customers comparing the RHT30 against the RHT35 should review both pages to confirm current configuration, included accessories, and delivery details before placing an order.

The RHT30 records humidity and temperature only, with memory allocated as 24,000 humidity points and 24,000 temperature points — the maximum per-channel capacity available in this family because there is no third channel competing for storage. For applications that do not require barometric pressure data, this allocation gives the RHT30 the longest single-session recording duration at any given sample rate.

The comparison table that follows highlights the practical split between the two models. The RHT30 covers humidity at 0.1 to 99.9% RH (±3% RH, 0.1% RH resolution) and temperature at -22 to 158°F (±1.0°F, 0.1° resolution) with 24,000 points stored per channel. The RHT35 covers the same humidity and temperature ranges with the same accuracy and resolution, and adds barometric pressure at 300 to 1100 hPa (8.9 to 32.5 inHg) with ±3 hPa accuracy and 0.1 hPa (0.1 inHg) resolution.

Memory allocation is the other key difference. Because the RHT35 records three channels instead of two, each channel is allocated 16,000 points rather than the 24,000 per channel in the RHT30. Both units share the same overall memory pool and the same 30-second to 2-hour sample rate range; the choice between them comes down to whether barometric pressure is part of the measurement requirement, and how that affects the duration of an unattended recording session at the customer's chosen sample interval.

Additional differences in specifications beyond the few shown above are not listed here — see each model's full specifications below.

Accessories Supplied

• (2) CR2032 batteries
• USB cover (can be used as a stand)
• Wall mounting screw
• Built-in hanger

Product Core & Specifications

Please review the Manufacturer's Data Sheet to verify published specifications. Feedback on this webpage is always welcome — please reach out to your Test Architect at any time for questions or concerns. Thank you, we truly appreciate you being our customer.