Real time monitoring data of digital gas mass flowmeter

1、 Basic measurement parameters

measuring mediumSupports measuring gas types such as air, nitrogen, oxygen, argon, carbon dioxide, etc. Some models can measure mixed gases (requiring prior calibration).

Measurement range (range): Refers to the flow range that can be effectively measured, usually expressed in mass flow units (such as 0.1-100 g/h, 1-1000 L/min), with a range ratio (maximum flow/minimum flow) of 10:1 to 100:1 or even higher.

accuracy classThe indicators for measuring accuracy are commonly expressed as "± X% FS (full range)" or "± X% RD (reading)", such as ± 1% FS, ± 0.5% RD+0.2% FS, and high-precision models can reach ± 0.2% RD.

repetitivenessThe consistency of multiple measurements is usually ± 0.1%~± 0.5% RD, and the better the repeatability, the higher the data stability.

2、 Environmental and working condition parameters

Operating Temperature：

Medium temperature: refers to the temperature range of the measured gas, generally from -20 ℃ to 80 ℃, and some high-temperature models can reach above 150 ℃.

Environmental temperature: The ambient temperature at which the flowmeter operates is usually -10 ℃~60 ℃, and exceeding this range may affect accuracy.

work pressureThe gas pressure range that the equipment can withstand is commonly 0~1 MPa, 0~2 MPa, and high-pressure models can reach more than 10 MPa, which needs to be matched with the pressure of the pipeline system.

Humidity and protection levelAdaptation range of environmental humidity (such as 0-95% RH, no condensation), protection level (such as IP65, dust and low-pressure water spray).

3、 Output and display parameters

Display contentThe digital display screen can display real-time parameters, including instantaneous flow rate (units: g/s, L/min, etc.), cumulative flow rate (units: kg, m ³, etc.), medium temperature, pressure, etc.

output signal：

Analog output: 4-20 mA, 0-5 V, 0-10 V, etc., used for connecting with PLC, DCS and other systems.

Digital output: RS485 (Modbus RTU protocol) RS232、 Pulse signals (corresponding to cumulative flow), etc., support data communication and remote monitoring.

response timeAfter the flow rate changes, the time for the output signal to stabilize is usually 100 ms~1 s, and the fast response model can be within 50 ms.

4、 Other parameters

power supplyCommon DC 24V, some support AC 220V or battery power supply (suitable for portable scenarios).

Installation methodPipeline type (flange, threaded connection), plug-in type (suitable for large pipe diameters), panel type, etc., need to match the pipeline size (such as DN10~DN2000).

materialThe material of the contact medium part of the sensor, such as stainless steel (304/316), aluminum alloy, polytetrafluoroethylene (corrosion-resistant scenario), etc.

2、 Two mainstream thermal measurement structures

Hot wire method (constant temperature difference method)

Real time monitoring of gas temperature using reference wire (T ₀);

The heating wire maintains a constant temperature difference with the gas through current (Δ T=T ₕ - T ₀, where T ₕ is the temperature of the heating wire);

When the gas flow rate increases, the amount of heat carried away increases, and the heating current needs to be increased to maintain Δ T constant;

By measuring the change in heating current, the gas mass flow rate can be converted (the current is proportional to the flow rate).

structureInstall two hot wires (usually platinum wires) in the gas flow channel, one serving asheating wire(Maintain a constant high temperature), the other one serves asReference silk(Sensing gas temperature).

working process：

Apply to the hot filmconstant powerMaintain a certain temperature with an electric current;

When gas flows, it carries away heat, causing a decrease in the temperature of the hot film, and the temperature change is related to the flow rate;

Calculate the flow rate by measuring the temperature change (or resistance change, as metal resistance changes with temperature) of the hot film.

structureUsing metal thin film (such as nickel chromium alloy) as the heating element, deposited on a ceramic substrate, with both heating and temperature measurement functions.

working process：

3、 Key advantages and technical points

Directly measure mass flow rateWithout the need for temperature and pressure compensation like volumetric flow meters, it can directly output mass flow rates (units: kg/h, g/s, etc.) with higher accuracy.

wide range ratioThanks to the linear characteristics of the thermal principle, the range ratio can reach 100:1 or even higher, covering small flow rates (such as mL/min level) to medium to large flow rates (such as m ³/h level).

Adaptability to gas typesBy calibrating the thermal properties parameters (such as specific heat capacity) of different gases, multiple gases (air, nitrogen, oxygen, etc.) can be measured, and some models support custom calibration for mixed gases.

Fast response speedThe thermal inertia of hot wire/hot film is small, and the response time to flow fluctuations is usually in the millisecond range, making it suitable for dynamic flow measurement.

Real time monitoring data of digital gas mass flowmeter