Extech RHT35 USB Humidity / Temperature / Barometric Pressure Datalogger

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The Extech RHT35 is an easy-to-use USB Datalogger that records Humidity, Temperature and Barometric Pressure with Date/Time Stamp

The RHT35 uses a standard USB connection to transfer up to 48,000 readings to a PC with data/time stamp in PDF or spreadsheet format.

Additional features include an 8-location logger bookmark, 6-language options, programmable sampling interval, adjustable alarm, and password-protected security log-in.

Large LCD optimizes viewing and the smart LED provides color-coded humidity, temperature, and barometric pressure reading status.

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pdf_sml    Extech RHT35 Datasheet

pdf_sml    Extech RHT35 User Manual

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Extech RHT35 USB Humidity / Temperature / Barometric Pressure Datalogger


The Extech RHT35 USB Humidity / Temperature / Barometric Pressure Datalogger is similar in size to  a large key fob, and is designed for everyday use in troubleshooting HVAC/R and indoor air quality (IAQ) issues related to temperature, humidity and barometric pressure.

HVAC/R technicians, commercial facilities managers, IAQ professionals and workplace health managers alike can use the RHT35 to monitor a location for an extended period of time in response to occupant complaints or as part of standard predictive maintenance.

Users can “set and forget” the dataloggers with a customizable recording rate from once every 30 seconds to once every 2 hours and a capacity of up to 48,000 combined, total readings with date and time stamps. For multi-site logging, readings can be associated with up to 8 locations. Technicians and occupants can quickly check current readings on the large, high visibility LCD. The MAX/MIN button allows quick access to the highest and lowest readings recorded. High and low thresholds can also be configured to trigger a red flashing LED alarm indicator. When reporting is required, the dataloggers can be connected to a PC or laptop to easily output readings in a Microsoft Excel or Adobe PDF format.

Extech RHT35 USB Humidity/Temperature/Barometric Pressure Datalogger Features:

  • Compact size housing with built-in NTC thermistor, capacitive humidity sensor, and barometric pressure MEMS sensor designed with standard USB connector for easy data downloading to a PC
  • 5-digit LCD display with battery life indicator
  • User programmable settings: 6 languages, sample rate, start delay time, alarm delay time, high/low alarm range, and security feature
  • Status Indication via Red and Green LEDs
  • Start button begins continuous datalogging, which continues until memory is full at 48,000 readings (16K for each parameter), or when Stop button is pressed
  • Bookmark 8 locations in a data recording log with a press of the Mark button
  • Long battery life (approx. 3 months)
  • Generates a PDF report or Excel® spreadsheet with data and trending graph when plugged into a PC after datalogging is completed (Adobe® Reader® required)
  • Max/Min function
  • Includes 2 CR2032 batteries, USB cover (can be used as a stand), wall mounting screw, and built-in hanger

Extech RHT35 Specifications:

Specifications Range Max Resolution Basic Accuracy
Humidity 0.1 to 99.9% RH 0.1% RH ±3% RH
Temperature (Air) -22 to 158°F (-30 to 70°C) 0.1° ±1.0°F (±0.5°C)
Barometric Pressure 300 to 1100 hPa (8.9 to 32.5 inHg) 0.1 hPa (0.1 inHg) ±3 hPa
Datalogging interval 30 seconds to 2 hours
Memory Relative Humidity: 16,000 points, Temperature: 16,000 points, Barometric Pressure: 16,000 points
Dimensions/Weight 110 x 40 x 19mm / 90g 5