Humidity measurements don’t always happen in a laboratory. The MBW CALIBRATION™ Model 973™ Portable Chilled Mirror Hygrometer brings high-precision dew and frost point measurement directly to the measurement location.
Designed for both spot checks and continuous measurements, the Model 973 combines an integral chilled mirror measuring head with temperature and pressure measurement to provide precise humidity measurement in air and other gases. Its portable design makes it ideal for on-site dew point sensor calibration, compressed air systems, gas quality testing, dryer performance verification and production environments.
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What Is the MBW Model 973?
The MBW Model 973 is a portable chilled mirror hygrometer designed for precise spot and continuous measurement of dew point, frost point and temperature in air and other gases. It uses the chilled mirror condensation principle to directly determine dew or frost point and also measures pressure and temperature for calculating additional humidity parameters.
The Model 973 is designed for applications where users need high-quality humidity measurements outside a permanent laboratory or fixed installation.
The Model 973-SF6 Dew Point Chilled Mirror Analyzer is primarily used in the electrical power industry for the measurement of moisture content in SF6 gas insulated equipment such as gas-insulated switchgear (GIS) and circuit breakers. This is because moisture can cause insulation failure and equipment damage in these applications.
It can also used in other industries that use SF6 gas such as the semiconductor industry, which uses SF6 gas as a dielectric gas for plasma etching, and the magnesium industry, which uses SF6 gas as a cover gas in the casting process.
Spot Checks
Take the Model 973 directly to individual measurement points to check:
- Compressed-air lines
- Dryer outlets
- Gas systems
- Production areas
- Storage environments
- Installed dew-point sensors
Continuous Measurement
Connect the instrument to a sample stream for ongoing measurement when a longer measurement period is required.
Process Insights explicitly states that the 973 supports both spot and continuous measurement of dew/frost point in air and other gases.
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Which Model 973 Do I Need?
| Model | Best For | Positioning |
|---|---|---|
| 973™ | General portable measurement | Spot & continuous dew/frost-point measurement |
| 973S™ | Standard portable applications | Integrated sample pump & external temperature measurement |
| 973L™ | Low-range applications | Optimized response injection system for fast measurements |
| 973CA™ | Compressed air/high-pressure systems | On-site compressed-air measurement & validation |
| 973-SF6™ | Electrical power/GIS | Humidity, SF6 purity & SO2 measurement |
The current Process Insights portfolio identifies the 973L as the low-range version, the 973S as the standard version with integrated sample pump, the 973CA for compressed-air/high-pressure systems, and the 973-SF6 for gas-insulated switchgear applications.
Dew Point or Frost Point?
This is an excellent AEO section because the Model 973 datasheet provides a clear technical explanation.
Below 0°C, Knowing the Condensate Phase Matters.
At temperatures below 0°C, water vapor can condense on the mirror as either liquid water or ice. That distinction matters because dew point and frost point are not necessarily the same temperature. The Model 973 documentation states that the difference can reach up to approximately 3°C, meaning the condensate phase needs to be known for correct calculation or validation of humidity parameters such as relative humidity.
The Model 973 includes ForceFrost™, which helps establish a known frost condition during low-temperature measurements. Below a user-defined temperature, ForceFrost overcools the mirror to encourage the condensed layer to transition to the solid phase. This helps eliminate uncertainty over whether the instrument is measuring dew point or frost point.
The Model 973 includes an integrated Ice-Test function that allows users to check instrument calibration stability.
Customer Challenge – “Below freezing, how do I know whether I’m actually measuring dew point or frost point?”
Model 973 Solution
ForceFrost™ helps establish a known frost condition for greater measurement confidence.
No Routine Humidity Sensor Replacement.
- No routine humidity sensor replacement
- No routine calibration adjustment
- Accessible mirror cleaning
- Integrated Ice-Test verification
Key Customer Challenges
“Can I trust the installed dew point sensor?”
Use the 973 as an independent portable chilled mirror reference for on-site measurement and sensor verification.
“I have multiple measurement locations. Do I need an analyzer at every point?”
The portable 973 can be moved between locations and is supplied with a protective transport case.
“Do I need a spot check or continuous measurement?”
The 973 supports both.
“Below freezing, am I measuring dew or frost?”
ForceFrost helps establish the solid condensate phase and reduce uncertainty.
“How do I know my instrument is still stable?”
Use the integrated Ice-Test function to check calibration stability between formal calibrations.
OUR Dew Point Chilled Mirror Hygrometer Analyzer SOLUTIONS
MODEL 373™
MODEL 473™
MODEL 573™
T12 Thermometer
TempControl™ Software
GECKO R2™ Metrology Software
MODEL 973™
MODEL 973L™
For low range specifications
MODEL 973S™
Standard Version
MODEL 973 SF6™