The Extech RHT30 and RHT35 are compact USB dataloggers that record relative humidity and temperature, with the RHT35 adding barometric pressure measurement through a built-in MEMS sensor. Each unit houses a built-in NTC thermistor and a capacitive humidity sensor in a small housing fitted with a standard USB connector, so logged data downloads directly to a PC. A large LCD optimizes viewing, and a smart LED provides color-coded humidity, temperature, and barometric pressure reading status.

A datalogger captures measurements at set intervals over time, building a time-stamped record that can be reviewed long after the readings were taken. The RHT-series begins continuous datalogging when the Start button is pressed and continues until memory is full at 48,000 readings or until the Stop button is pressed, transferring up to 48,000 readings to a PC with date/time stamp in PDF or spreadsheet format.

ValueTronics stocks and holds its own inventory in a 20,000 sq ft secure warehouse at 1675 Cambridge Drive in Elgin, Illinois.

Brand Heritage

Extech Instruments is a measurement-instrument brand that operates under FLIR Systems, Inc. FLIR Systems became part of Teledyne Technologies in 2021, placing the Extech line within the Teledyne family of brands.

Compare Other Models in This Series

The RHT30/RHT35 series consists of two USB dataloggers that share the same compact housing, large LCD, color-coded status LED, and direct-to-PC USB download. Both models record relative humidity and temperature and generate a PDF report or Excel spreadsheet with a trending graph once datalogging is complete.

The two models differ in measurement scope and memory allocation: the RHT30 logs humidity and temperature, while the RHT35 adds barometric pressure through a built-in MEMS pressure sensor.

Each model below is its own dedicated product page with new-matched pricing. Select the model that fits your measurement requirements, then open the new listing for that model to see its current availability and price.

The primary difference is barometric pressure: the RHT35 includes a built-in MEMS pressure sensor measuring 300 to 1100 hPa (8.9 to 32.5 inHg), a capability the RHT30 does not provide. Memory is also allocated differently — the RHT30 stores 24,000 humidity points and 24,000 temperature points, while the RHT35 stores 16,000 points each for humidity, temperature, and barometric pressure. Both reach the same 48,000-reading total. See the comparison table below for the per-model breakdown.

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

Important: Adobe Reader is required to view the generated PDF report.

Important: Generating the PDF report or Excel spreadsheet after datalogging requires Adobe® Reader® on the connected PC.

Important: Barometric pressure measurement is available on the RHT35 model only; the RHT30 records Humidity and Temperature only.

About this New unit

This is a brand-new, factory-sealed unit, supplied exactly as it arrives from the manufacturer and backed by the full manufacturer warranty. For the exact configuration, available options, included accessories, or current lead time for your application, our Test Architects can confirm the details before you order.

ValueTronics supplies both new and used test and measurement equipment. New units ship factory-sealed, exactly as received from the manufacturer; every used unit is inspected and functionally verified in-house at our 20,000 sq ft secure facility in Elgin, Illinois before it ships. Our Test Architects can help you select the condition, calibration, and configuration that fit your application.

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.