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Moisure Sensor

High Temperature Absolute Humidity Sensor for Humidity Measurement

The MAC 125 Moisture Analyzer is different from other comparable products in that it uses no chemicals, compressed air, wet bulb techniques, optics or mirrors. Instead, its moisture sensor and humidity meter relies on a patented, proprietary solid state humidity measurement process. This product incorporates a humidity sensor that provides a humidity reading based on the partial pressure of water vapor. The probe is protected from particles by a 10-micron ceramic filter element that is cleanable and replaceable.

What this means to you as a user is that you get the most accurate readings even in the most difficult, high-temperature operating environments. This moisture sensor gives users access to an original, innovate method of absolute humidity measurement. This makes it easier for you to improve your moisture control strategy.

Both the sensor and humidity meter have been designed to be exceedingly service-friendly. The moisture/humidity sensor is capable of giving precise readings at nearly any process temperature range.

MAC 125 Overview

  • The MAC125 is the latest, and most advanced variety of Absolute Humidity Meters from MAC Instruments. The MAC125 humidity sensor and its predecessors have produced the trusted Humidity Sensors across the globe since 1990. Accuracy and reliability in high temperature moisture measurement are the hallmarks of all our products.
  • Aware of the installation and mounting difficulties associated with competitors’ products, MAC Instruments has made a concerted effort to provide our moisture sensor with a no-fuss mounting capability. It can be mounted in a matter of minutes to stacks, ducts, flues, ovens, furnaces, calciners, kilns, dryers, fuel cells, etc.
  • An easy-to-read humidity display meter is another highlight of the product. All important figures can be noted at a glance. MAC Instruments offers the MAC 125 in analog as well as digital models.

Here’s more on why the MAC 125 moisture sensor and humidity meter is a prudent investment:

  • Measure Absolute Humidity to Virtually Any Temperature
  • Measure moisture in a flame
  • 2 Voltage Options
    • 120V / 60Hz
    • 230V / 50Hz
  • Jumper Selectable Scales
    • % Moisture by Volume
    • Humidity ratio (lb water vapor / lb dry air) (g water vapor / g dry air)
  • In-Situ Measurement
    • Mounts directly to stacks, ducts, flues, ovens, furnaces, calciners, kilns, dryers, fuel cells, etc.
  • NEMA 4X / IP53 Water Proof Design
    • Suitable for outdoor installation
  • Standard Signal Outputs (Jumper Selectable)
    • 0-20mA ( 0 to 5V with 250 Ohm load )
    • 4-20mA ( 1 to 5V with 250 Ohm load)
  • Severe Duty Industrial Construction
    • Stainless steel barrel
    • Cast aluminum enclosure
  • Automatic Altitude / Pressure Compensation
Model % Moisture By Volume Humidity Ratio
MAC125-100-120V 0 to 100% 0 to 10
MAC125-60-120V 0 to 60% 0 to 1
MAC125-30-120V 0 to 30% 0 to 0.25
MAC125-20-120V 0 to 20% 0 to 0.15
MAC125-10-120V 0 to 10% Not Available

Temperature Range

  • 40° F / 4° C to 1200° F / 650° C – Above 1200° F requires special mounting tube

Pressure Range

  • 1 Atmosphere ± 5 PSI / 35 kP


  • ± 1% of %Mbv Full Scale


  • ± 1 % of %Mbv Full Scale


  • ± 1 % of %Mbv Full Scale

Response Time

  • 120 Seconds or less to reach 90% of final value

Analog Output

  • ± 1 % of %Mbv Full Scale

Power Requirements

  • 120V / 60 Hz or 230V / 50 Hz, 3A max (Specify required voltage when ordering)


  • Digital Display (Built into MAC125)
  • Case Cool Soleniod valve (requires 10 PSI / 69 kPa Clean, Dry Air) for Operation at High Ambient Temperature
  • Filter Blow Back Soleniod valve (requires 10 PSI / 69 kPa Clean, Dry Air) filter can be blown out by closing an external contact or by setting a time for the valve to open for 2 seconds daily (jumper selectable)
  • Various Standard and Custom Mounting Tubes and Adapters

PDFView the MAC125 data sheet in pdf form.