Extech RH300 Digital Psychrometer User Manual

Product Overview

The Extech RH300 is a compact digital psychrometer designed for field applications, providing simultaneous measurements of relative humidity, air temperature, dew point, and wet bulb temperature. Its robust design includes a unique sensor cap for protection during storage.

This device is capable of calculating T1-T2 differential (air temperature minus external probe temperature) when an optional TP890 probe is used, and also T2 minus dew point. Advanced features include Data Hold, selectable Auto Power Off, and MAX/MIN/Average reading capabilities.

Figure 1: Front view of the Extech RH300 Digital Psychrometer, showing the display and control buttons.

Safety Information

Please read and understand all safety precautions before operating the Extech RH300. Failure to follow these instructions may result in injury or damage to the device.

• Do not expose the device to extreme temperatures or direct sunlight for prolonged periods.
• Avoid dropping the device or subjecting it to strong impacts.
• Do not attempt to disassemble or modify the device. Refer all servicing to qualified personnel.
• Ensure proper battery installation and disposal according to local regulations.
• Keep the sensor cap closed when the device is not in use to protect the sensor.

Setup

Battery Installation

The Extech RH300 requires two AAA (1.5V) batteries for operation. Follow these steps to install the batteries:

1. Locate the battery compartment cover on the back of the device.
2. Slide the cover open in the direction indicated by the arrow.
3. Insert two AAA batteries, ensuring correct polarity (+ and -) as marked inside the compartment.
4. Close the battery compartment cover securely until it clicks into place.

Figure 2: Rear view of the Extech RH300, showing the battery compartment and two AAA batteries.

Initial Power On

After installing the batteries, press the ON/OFF button to power on the device. The display will illuminate and show the current humidity and temperature readings.

Operating Instructions

Taking Measurements

To ensure accurate readings, allow the device to stabilize in the measurement environment for a few minutes. Keep the sensor clear of obstructions.

• Relative Humidity (%RH): Displayed on the top line of the LCD.
• Air Temperature: Displayed on the middle line of the LCD.
• Dew Point (DP) / Wet Bulb (WB): Press the T/DP or T2/WB button to cycle between these readings on the bottom line of the LCD.

Unit Selection (°C/°F)

Press the °C/°F button to switch between Celsius and Fahrenheit temperature units.

Data Hold Function

Press the HOLD button to freeze the current readings on the display. Press HOLD again to release and resume live measurements.

MAX/MIN/Average Readings

The RH300 can record maximum, minimum, and average readings. To access these functions:

1. Press the RESET MN/MX button once to display the maximum recorded values.
2. Press it again to display the minimum recorded values.
3. Press it a third time to display the average recorded values.
4. To clear the recorded MAX/MIN/Average values, press and hold the RESET MN/MX button until the display resets.

Auto Power Off

The device features a selectable Auto Power Off function to conserve battery life. Refer to the full manual for details on enabling or disabling this feature.

Maintenance

Cleaning

Wipe the device with a soft, damp cloth. Do not use abrasive cleaners or solvents. Ensure the sensor area remains clean and free of dust or debris.

Storage

When not in use, store the RH300 in a cool, dry place. Always close the sensor cap to protect the humidity sensor from damage and contamination. Remove batteries if storing for extended periods to prevent leakage.

Calibration

The Extech RH300 is factory calibrated. For professional applications requiring periodic recalibration, contact Extech customer support or an authorized service center. Calibration kits (e.g., RH305) may be available for user calibration at specific humidity levels.

Troubleshooting

Specifications

Figure 3: Extech RH300 with approximate dimensions indicated.

Warranty Information

The Extech RH300 Digital Psychrometer comes with a 1-Year Limited Warranty from the date of purchase. This warranty covers defects in materials and workmanship under normal use. It does not cover damage resulting from misuse, abuse, accident, unauthorized alteration or repair, or acts of nature.

For warranty service, please retain your proof of purchase and contact Extech customer support.

Customer Support

For technical assistance, troubleshooting, or service inquiries, please visit the official Extech website or contact their customer support team.

• Extech Website: www.extech.com
• Online Support: Refer to the support section on the Extech website for FAQs, downloads, and contact forms.