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Brand: Micro Motion
Micro Motion GDM Gas Density Meter
Description
Fast-response gas density measurement with a vibrating cylinder
The Micro Motion Gas Density Meter (GDM) uses a Ni-Span C vibrating cylinder to measure gas density directly over a wide operating range. The datasheet describes it for high-value gases such as natural gas, fuel gas and hydrogen at up to 257 °F (125 °C) and 2,900 psi (199.95 bar), and states that the measurement is unaffected by changes in gas composition.
Technical specifications
| Parameter | Specification |
|---|---|
| Datasheet | PS-001483, Rev G, February 2024 |
| Model | GDM gas density meter with Viton O-rings; sensor calibration range codes selected at ordering |
| Density range | Up to 400 kg/m3 (25 lb/ft3) |
| Accuracy | Argon and nitrogen ±0.1% of reading; natural gas and ethylene ±0.15% of reading; hydrogen and helium ±0.5% of full scale |
| Repeatability | ±0.02% of reading |
| Maximum operating pressure | 200 barg (2,900 psi) |
| Temperature range | Standard -20 °C to +85 °C; high-temperature model -20 °C to +125 °C |
| Temperature coefficient | 0.001 kg/m3 per °C; integral 100 ohm RTD, DIN 43760 Class A |
| Process gas | Must be dry, dust free and compatible with Ni-Span C 902, 316L stainless steel and Stycast catalyst 11 |
| Outputs | Analog 4-20 mA with HART, discrete, Time Period Signal, fixed output and 2-wire TPS versions; Modbus RS-485; WirelessHART via THUM adapter |
| Enclosure | IP66/67, NEMA 4X, aluminium or stainless steel housing |
| Weight | About 11 lb (5 kg) aluminium; about 17 lb (8 kg) stainless steel; thermowell pocket about 13 lb (6.5 kg) |
| Hazardous area | ATEX II 2G Ex ia IIC T4 (with display) or T6 (without); IECEx Ex ia IIC; CSA C-US Class I Div. 1 Groups A to D; ambient -40 °F to 149 °F (-40 °C to 65 °C) |
| Retrofit | Same form and functionality as the Micro Motion 7812 gas density meter |
Applications, outputs and installation
The datasheet states compliance with AGA 3 and conformity with ISO 5167 and ISO 15970 for use in gas measurement. Derived outputs include density at reference conditions and molecular weight, and with an external flow input the meter can report mass flow and base density through its HART I/O. Known Density Verification and other diagnostics support meter health checks. In hazardous areas the meter needs safety barriers or galvanic isolators between it and the signal processing equipment, and the datasheet lists barrier and isolator kits for the 4-wire and 2-wire versions. The meter pairs naturally with the Coriolis meters on this site, for example the Micro Motion ELITE CMF series.
The sensor calibration range is chosen at ordering. For example, calibration code 1 gives ±0.1 percent of reading accuracy for densities with a low limit of 1.5 kg/m3 and a high limit of 10 kg/m3, so match the code to the gas density window at operating pressure. The sensor uses a class A RTD to correct for temperature, ProLink III software handles configuration and diagnostics, and newly shipped devices carry a QR asset tag that links to serialized documentation.
What to confirm before ordering
- Gas composition, dryness and cleanliness, since the sensor requires dry, dust-free gas
- Calibration range code and accuracy needed for the gas density window
- Temperature rating (standard or high-temperature) and operating pressure
- Output version and the barrier or isolator kit required for the hazardous area
- Housing material and thermowell pocket if one is required
How the Micro Motion GDM works
A thin metal cylinder is set to vibrate at its natural frequency while the gas flows around it. The heavier the gas, the lower the frequency. The electronics read the frequency, correct it for temperature and calculate the density. This gives a direct reading without the need to know the gas composition.
Where the GDM is used
- Natural gas measurement
- Fuel gas lines
- Hydrogen and helium duties
- Ethylene and other process gases
- Retrofit of the earlier 7812 meter
Selection checklist for the GDM
- Gas type and density range
- Operating pressure up to 200 barg
- Temperature, standard or high
- Output type: 4-20 mA with HART, Modbus or period signal
- Housing: aluminium or stainless steel
- Hazardous area rating
- Thermowell pocket need
- Gas cleanliness and dryness
Installation, commissioning and maintenance notes for the GDM
Fit the meter where the gas is dry and free of dust. Wire it through safety barriers in hazardous areas. Check the output against the calibration sheet. Run the density verification at the set interval and look at the diagnostics.
Requesting a quotation for the Micro Motion GDM
Please send the gas, the pressure, the temperature and the output wanted. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.
GDM density range
The meter reads density up to 400 kg/m3.
GDM accuracy
The accuracy is 0.1 percent of reading on argon and nitrogen, and 0.15 percent on natural gas and ethylene.
GDM repeatability
The repeatability is 0.02 percent of reading.
GDM pressure limit
The maximum operating pressure is 200 barg, which is 2,900 psi.
GDM temperature range
The standard model works from minus 20 to 85 degrees C and the high-temperature model to 125 degrees C.
GDM outputs
The outputs include 4-20 mA with HART, Modbus RS-485 and a time period signal.
GDM enclosure
The enclosure is rated IP66/67 and NEMA 4X.
GDM weight
The aluminium housing weighs about 5 kg and the stainless steel housing about 8 kg.
Meter records for the GDM
Record the verification results, the output scaling and the date of each check.
Choosing the right GDM output
Use HART for a loop-powered signal and Modbus where a serial link to the controller is in place.
Documents and quotation
The Micro Motion Gas Density Meters datasheet (PS-001483 Rev G, February 2024) is available from the product documents on this page. Seven Star LLC is an independent supplier in Muscat; send the complete order code from the nameplate or your specification and we will check it against the manufacturer documentation before quoting. Browse more flowmeters in the catalogue.
Datasheets & Documents
- Datasheet Micro Motion Gas Density Meters datasheet PS-001483 Rev G (February 2024) Download
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About brand
Coriolis flow and density meters have carried the Micro Motion name since 1977, when the company started in Boulder, USA. A Coriolis meter measures mass flow directly and reads density from the same tubes. Seven Star LLC, an independent supplier in Oman, lists the Micro Motion ELITE CMF400 Coriolis flow and density meter and the compact G-Series, and sources Micro Motion flow meters by complete model code.
Micro Motion meter families
ELITE is the manufacturer's top performance family for flow and density, and the CMF400 is one of its larger line sizes. The G-Series is a newer, very compact family for general duty. Each sensor is paired with a Coriolis transmitter, and the range also includes density and viscosity meters. Liquids, gases and slurries can all be measured, which is why these meters appear in oil and gas, refining, chemical, food and marine service.
Ordering Micro Motion meters: what we need
A Micro Motion sensor and its transmitter each have their own model code and serial number; send both. For a new meter we need the fluid, flow range, density, viscosity, operating pressure and temperature, line size, process connection and rating, wetted material, hazardous area approval, outputs and protocol. Custody transfer duty in the GCC should be stated up front because it changes the approvals and calibration options requested.
Browse Micro Motion products by category: Flowmeters.
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Frequently Asked Questions
How does the GDM measure gas density?
A Ni-Span C cylinder vibrates at its natural frequency inside the gas; the frequency changes with the density of the surrounding gas.
What accuracy does the GDM have?
±0.1% of reading on argon and nitrogen, ±0.15% on natural gas and ethylene, and ±0.5% of full scale on hydrogen and helium.
What are the pressure and temperature limits?
Up to 200 barg (2,900 psi); -20 °C to +85 °C for the standard model and -20 °C to +125 °C for the high-temperature model.
What gas quality is required?
The gas must be dry and dust free and compatible with Ni-Span C 902, 316L stainless steel and Stycast catalyst 11.
Does it replace the 7812?
The datasheet states full backwards compatibility with the Micro Motion 7812 gas density meter.
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