Since 1993, the Fluke Calibration molbox/molbloc flow calibration system has enabled labs to measure gas flow in a variety of measurement devices. Offering some of the lowest uncertainties in the industry, molbox takes real-time flow measurements so that technicians get an accurate picture of the performance of their device under test (DUT).
Now, the next-generation molbox2 system improves upon this precision and performance and expands uncertainty ratings to more than 30 gases. This application note details the improvements of the new molbox2 system, how it works, and how professionals in the semiconductor, pharmaceutical, and natural gas industries can apply this cutting-edge system to meet their industry’s needs.
How the molbox2 System Works
Like molbox1+, the molbox2 system features a molbox flow terminal with a display that connects to the molbloc-L laminar flow element and the molbloc-S sonic nozzle element. If you already have a set of molbloc elements from your molbox1+ system, you can likely keep using them with molbox2: The upgraded flow terminal is backwards-compatible with almost all molbloc elements.
The molbox2 system measures a continuous flow of gas through the molbloc elements that can be compared to a DUT for real-time measurement. You can also adjust flow output during a test, either manually or with analog control, which is a key advantage of the molbox system. Doing so allows metrologists to capture performance data modeled after real-world conditions. COMPASS® for Flow software is also compatible with molbox2 for test automation, which produces quick, easy, and repeatable measurements.
Functionally, molbox1+ and molbox2 operate the same way. You can set up tests manually or via COMPASS® for Flow, and you can adjust test conditions by adding molbloc elements or changing gas flow. The main difference between molbox1+ and molbox2 is their specifications: Compared to molbox1+, molbox2 offers more gas calibration choices, expanded uncertainty specification options, and decreased calibration time.
More Options, Faster Calibration: New Upgrades With molbox2
Here are the main differences between molbox1+ and molbox2 at a glance. Below, we’ll get into the specifics of everything molbox2 offers.
| Feature | molbox1+ | molbox2 |
| Gases available for calibration | 20 | 30+ (custom mixtures available) |
| Uncertainty rating availability | Nine gases | All 30+ gases |
| Flow response speed | Standard | 3× faster |
| Gas uncertainty specs | Only for gases directly calibrated | All 30+ using N₂ calibration and REFPROP 10 |
| Custom gases | Limited | Available for all gases with available NIST data |
| molbloc-L and molbloc-S compatibility | Yes | Yes, backwards-compatible for most models |
| COMPASS® for Flow compatibility | Yes | Yes |
Faster and More Accurate Flow
When it comes to flow response speed, molbox2 outputs data three times faster than molbox1+, helping you finish calibrations more quickly. But it’s not just speed that molbox2 brings to the table — its calculations are also more accurate than molbox1+: Compared to molbox1+, molbox2 uses an enhanced laminar flow calculation from NIST that provides better precision.
Plus, with molbox2, you can employ most existing molbloc-L and molbloc-S elements for flow calculations. For molbloc-L, there’s an upgrade available to use an enhanced laminar flow calculation from the National Institute of Standards and Technology (NIST) based on the REFPROP 10 database. REFPROP 10 is a detailed repository of industrial fluids that helps create accurate uncertainty predictions for a wide variety of gases.
With the upgrade, molbox2 and molbloc-L can flow any gas in the molbox2 library within a stated uncertainty specification using just an accredited nitrogen gas (N2) calibration.
Bigger Gas Library
Where the molbox1+ gas library featured 20 gas calibration options, molbox2 boosts that offering to 27gases. The seven gas types we’ve added to our database with this update include:
- Propylene
- Acetylene
- Neon
- Krypton
- Isobutane
- Deuterium
- Natural gas
Plus, custom gas mixtures are available upon request, as long as the National Institute of Standards and Technology (NIST) provides gas property information. In fact, our gas library exceeds 60 including custom gases. That said, we cannot produce mixtures that are corrosive or incompatible with molbox/molbloc components.
Tailored mixtures are especially helpful for customers in fields like oil and gas, where natural gas mixtures vary between site locations. You want accurate calibrations every time — and that starts with the right gas mixture for your system. Fluke Calibration customer service is ready to help you build the mixture you need, when you need it.
Uncertainty Ratings for More Gases
With molbox1+, Fluke Calibration provided uncertainty ratings for nine gases: nitrogen, air, argon, helium, hydrogen, nitrous oxide, carbon dioxide, propane, and methane. This was due to the fact that we could only measure uncertainties of gases that we could actually calibrate in our lab.
But with molbox2, we can now offer uncertainty specifications for more than 30 gases based on just a nitrogen gas (N2) calibration and REFPROP10 modeling from NIST. You no longer need to calibrate individual gases to get an uncertainty rating. You just need to calibrate N2, and REFPROP 10 will calculate the rest. This is a great option for customers who need gas calibrations that most calibration labs don’t offer, like sulfur hexafluoride (SF6) calibrations.
Continued Software Support
We updated COMPASS® for Flow for molbox2 compatibility. That means you can continue using our flagship flow calibration software for test automation, report generation, and tracing results over time.
Additionally, you no longer need to run firmware updates in order to add new gases to your library, further simplifying and speeding up your calibration process.
Industry Applications
Many industries rely on gas flow calibration to keep machines running. The precision and added capabilities of molbox2 are flexible and able to meet the needs of various applications. These include:
- Semiconductors: Use molbox2 to calibrate mass flow controllers (MFCs) during production.
- Pharmaceuticals: Calibrate MFCs or bioreactor gases with stock or custom gas mixtures.
- Healthcare: Calibrate custom gases like heliox for hospital equipment like respirators.
- Oil and gas: Calibrate mixtures of natural gas blends and adjust for field-specific ratios. (Note that we do not flow oil and only calibrate gases.)
All that said, manufacturers and customers must supply their own gases for calibration; we do not offer gases for purchase.
Precision Is on Your Side With molbox2
The molbox2 system is ideal for flow applications where minimizing measurement uncertainty is a must. Whether you need to calibrate MFCs or natural gas mixtures after extraction, molbox2 makes it simple and fast to get the precise measurements you need.
With significant performance and capability upgrades from molbox1+, molbox2 will give your lab the boost it needs to improve flow calibration accuracy and speed. It will easily slot into labs already using the molbox/molbloc system. The Fluke Calibration team is ready to assist you with performance information and custom gas mixtures when you’re ready. Contact us to get started.