Skip to Main Content
  • Instrumart
Instrumart logo
  • Products
  • Brands
  • Applications
  • Lab
  • Blog
  • Account
  • Email Us
  • 1-800-884-4967
  • What can we help you find?

    Can’t find what you’re looking for? Contact one of our engineers today. We’re open Mo-Th 8am to 5:30pm. Fr 8am to 5pm ET.
    • 1-800-884-4967
    • Email Us
    • Live Chat

Instrumart will be having an all company meeting from 9AM to 10AM Eastern time today. 

Phones will be off during this time, please feel free to leave a message, email us at sales@instrumart.com, or call back after 10AM. 

  1. Humidity Meters

Testo 650 Humidity Meter

Reference class humidity measuring instrument with an accuracy of ±0.01 AW.

Testo 650 Humidity Meter
Testo 650 Humidity Meter
  • Testo 650 Humidity Meter
    Testo 650 Humidity Meter
  • Testo 650 Precision Humidity, Temperature and Pressure Meter
    Testo 650 Precision Humidity, Temperature and Pressure Meter
Testo 650 Humidity Meter
Testo 650 Humidity Meter
Testo 650 Humidity Meter
Testo 650 Precision Humidity, Temperature and Pressure Meter
Retired products cannot be ordered
The Testo 645 Humidity Meter is the recommended replacement

View Company Reviewsby Trustpilot
Manufactured
  • By Testo
Includes
  • FREE Ground Shipping
  • FREE Lifetime Tech Support
Questions?
Call 1-800-884-4967 or email sales@instrumart.com. Open Mo-Th 8am to 5:30pm. Fr 8am to 5pm ET.
Trustpilot

Overview

Features

  • Professional users
  • Performs complicated measurements
  • Basic parameters for humidity, temperature and pressure
  • Optional CO2, rpm, current and voltage
  • AW Value (Water Activity)
  • Indicates Moisture Equilbrium
  • Clear graphics display
  • 3 User defined function buttons
  • 45000 LCD, 4 lines memory

Description

The Testo 650 precision humidity measuring instrument is a reference class meter that has everything the professional user needs to complete complicated measurement tasks efficiently, accurately and conveniently. While the Testo 650 is primarily a humidity meter, it also includes the basic parameters temperature and pressure measurments. The meter also has the option of measuring CO2, rpm, current and voltage.

Water activity is one of the most important parameters in respect of product quality in the food production sector. The aw value provides information on chemically non-bonded water. For this reason, it is an important parameter when determining the product quality in many foodstuffs. The water activity in food determines color, stability, taste and shelf life. Potential risks exist if the food has very high water activity and is not adequately refrigerated.

The Testo 650 reference measurement system sets standards in aw value measurement. The 650 has an accuracy ±0.01 aw and reproducibility of ±0.003 aw. The accuracy of the precision sensor has been proven in international inter-laboratory tests.

The trend display in the Testo 650 automatically indicates when the equilibrium moisture has been reached and the measurement is complete. Constant monitoring is therefore not required. The Testo 650 ensures the long-term stability of the measurement for years, i.e. frequent, time-consuming readjustments are no longer necessary.

The Testo 650 measuring system is traceable to national standards. Its supplied with a DKD calibration certificate if required. This also gives assurance in legal questions. Uncomplicated and reliable documentation of the measured results are available via an attachable printer or on a PC.

The Testo 650 meter is available as a meter only or in one of two kit options:

650 Ref. Class 1% RH Accuracy Kit:

  • 650 Reference Meter / Logger
  • 1% RH probe
  • Probe connection cable
  • Service case
  • Comsoft 3 Software
  • RS232 cable

650 Transmitter Field Calibration Kit:

  • 650 Reference Meter / Logger
  • 1% RH probe
  • Probe connection cable
  • Service case
  • 400/650 to Xmitter interface cable

Documents

Documents

  • Testo 650 Precision Humidity, Temperature and Pressure Meter (201 KB)
  • All possible part numbers

Accessories

Probes

Testo Carbon Monoxide Probe
Testo Carbon Monoxide Probe

Carbon monoxide ambient probe for the Testo 400, Testo 650 and Testo 330 meters .

$769.00 $692.10

Cables

Testo RS232 Cable
Testo RS232 Cable

Connects Testo 545/645 light meter to PC for data transfer.

$107.00 $96.30

Need Help? Call a Temperature engineer at 1-800-884-4967

We're open Mo-Th 8am to 5:30pm. Fr 8am to 5pm ET

David S. headshot David S.
Applications Engineer
Dwight M. headshot Dwight M.
Senior Applications Engineer
28 years at Instrumart
Shawn D. headshot Shawn D.
Senior Applications Engineer
20 years at Instrumart
Luke M. headshot Luke M.
Applications Engineer
5 years at Instrumart
Alex A. headshot Alex A.
Senior Applications Engineer
19 years at Instrumart
Ron J. headshot Ron J.
Temperature Engineering Lead
29 years at Instrumart
Rhys D. headshot Rhys D.
Applications Engineer
David S. headshot David S.
Applications Engineer
Dwight M. headshot Dwight M.
Senior Applications Engineer
28 years at Instrumart
Shawn D. headshot Shawn D.
Senior Applications Engineer
20 years at Instrumart
Luke M. headshot Luke M.
Applications Engineer
5 years at Instrumart
Alex A. headshot Alex A.
Senior Applications Engineer
19 years at Instrumart
Ron J. headshot Ron J.
Temperature Engineering Lead
29 years at Instrumart
Rhys D. headshot Rhys D.
Applications Engineer
David S. headshot David S.
Applications Engineer

Recently Viewed

Testo 650 Humidity Meter
Testo 650 Humidity Meter
United States Canada Mexico
Shop
Products
Brands
Applications
Support
Customer Service
Ask a Question
Live Chat
Track Order
Fraud Prevention
Financing
Our Company
Blog
About Us
Contact Us
Jobs
Travel Information
Our Team
Privacy Policy
Accessibility Statement
Connect
1-800-884-4967
sales@instrumart.com
Instrumart
35 Green Mountain Dr
S Burlington, VT 05403 US
Mo-Th 8:00am to 5:30pm ET
Fr 8:00am to 5:00pm ET
Join Us on Facebook
Follow Us on X

Instrumart is a member of a family of industrial stores

Instrumart Compressor World Pump World BioPharm World Filtration World Motion World Qualitrol Engineered Solutions Wholesale Air Pipe
© Instrumart 2025

Family of Industrial Stores

Welcome to our family of stores, your go-to source for a wide selection of commercial and industrial products in the flow control and automation sectors. Each store features a curated range of specialized industrial solutions, with many items designed to complement each other, ensuring you can find everything you need for your specific application. Explore the stores below to discover our extensive product offerings for your business needs.

  • Instrumart

    Shop Industrial and Laboratory Instruments.

    Shop Now!
  • Compressor World

    Shop Compressed Air Equipment.

    Shop Now!
  • Pump World

    Shop Industrial, Water, and Waste Water Pumps.

    Shop Now!
  • BioPharm World

    Shop Sanitary Process Solutions and Products.

    Shop Now!
  • Filtration World

    Shop Industrial Filters.

    Shop Now!
  • Motion World

    Shop Motion Control and Process Automation Systems.

    Shop Now!
  • Qualitrol

    Shop Remanufactured or Repair Automation Products.

    Shop Now!
  • Engineered Solutions

    Shop Custom Engineered and Manufactured Systems.

    Shop Now!
  • Wholesale Air Pipe

    Shop Air Piping.

    Shop Now!