Ultra Low Flow Controller - MicroTrak™ 101

Ultra Low Flow Mass Flow Meters & Controllers

As today's science and engineering focus more and more on micro technology, the requirement to be able to measure and control extremely low gas mass flows has become very important. With state-of-the-art sensor technology and highly engineered direct acting valve design, MicroTrak accurately measures and controls micro mass flows of gas previously thought by scientists to be too low for a repeatable reading.

Excellent accuracy (+/- 1.0% of full scale) and reliability (+/- 0.2%) coupled with unsurpassed instrument stability offer customers an instrument they can depend on, month after month, year after year.

 MicroTrak™ 101 Ultra Low Flow Controller

MicroTrak™ 101 Ultra Low Flow Controller




Technical Details

  • Suitable for most gases with flow rates down to 0.1 sccm (smlm)
  • Accuracy of +/- 1.0% of full scale
  • Repeatability of +/- 0.2% of full scale
  • 316 Stainless steel construction
  • Digital performance with maximum flexibility
  • Primary Standard calibration and NIST traceability
  • Dial-A-Gas Technology—10 preprogrammed gases or select your own
  • Unique Pilot Module allows control critical functions.
  • All functions also available via RS-232
  • Multi-drop RS-485
  • Traditional analog controls and outputs also included:
  • 4-20 mA
  • 0-5 VDC
  • 1-5 VDC
  • 0-10 VDC
  • Small footprint makes installation easy
  • 24 VDC power supply
  • CE approval
  • Digital communications solutions include: Foundation Fieldbus, Modbus RTU, and Profibus DP.
  • Add Compod for enhanced Modbus networking, digital relays, analog input, and pulse output

Product Information

As today's science and engineering focus more and more on micro technology, the requirement to be able to measure and control extremely low gas mass flows has become very important. With state-of-the-art sensor technology and highly engineered direct acting valve design, MicroTrak accurately measures and controls micro mass flows of gas previously thought by scientists to be too low for a repeatable reading.

MicroTrak is specifically designed for flow ranges under 4 sccm (smlm) with a minimum controllable mass flow rate of 0.1 sccm (smlm). MicroTrak is a specialized instrument for those who need accurate and reliable micro mass flow control of clean gases including corrosives and toxics. MicroTrak is also available with an innovative and user-friendly Pilot Module, a front-mounted or hand-held control device that allows users to Dial-A-Gas®, change flow rate, modify engineering units or re-configure the instrument. With the Pilot Module, the user can set zero, span and full scale for each of 10 different gases independently to accommodate unexpected application or system design changes.

Our digital communications solutions offer engineers and systems integrators, full system integration and networking capability with Sierra's mass flow controllers and meters. Digital communications solutions include: Foundation Fieldbus, Modbus RTU, and Profibus DP. For enhanced networking capability, including two digital relays, totalization, inputs, and display, add the Compod Control Module™ to easily program a wide veriety of common flow systems and process controls ranging from gas mixing and dilution to leak testing.


Operating Principle

The Capillary Thermal Operating Principle

The principles of capillary thermal mass flow controller technology operation.

The operating principle of the SmartTrak instruments is based on heat transfer and the first law of thermodynamics. During operation process gas enters the instrument’s flow body and divides into two flow paths, one through the sensor tube, and the other through the laminar flow bypass. The laminar flow bypass (often called LFE which stands for “laminar flow element”) generates a pressure drop, P1–P2, forcing a small fraction of the total flow to pass through the sensor tube (m1).

Two resistance temperature detector (RTD) coils around the sensor tube direct a constant amount of heat (H) into the gas stream. During operation, the gas mass flow carries heat from the upstream coil to the downstream coil. The resulting temperature difference (∆T) is measured by the SmartTrak microprocessor. From this, SmartTrak calculates the output signal. Since the molecules of the gas carry away the heat, the output signal is linearly proportional to gas mass flow.

Figures 1-2 and 1-3 show the mass flow through the sensor tube as inversely proportional to the temperature difference of the coils. The coils are legs of a bridge circuit with an output voltage in direct proportion to the difference in the coils’ resistance; the result is the temperature difference (∆T). Two other parameters, heat input (H) and coefficient of specific heat (Cp) are both constant. Through careful design and attention to these parameters, this output signal is made linear over the transducer’s normal operating range (Figure 1-4). As a result, the measured flow through the sensor tube is directly proportional to the gas flow in the main body.

In the SmartTrak mass flow controllers, the gas which flows through the monitoring section is precisely regulated by the built-in electromagnetic valve. The normally closed valve is similar to an on/off solenoid valve, except that the current to the valve coil, and hence the magnetic field, is modulated so that the ferromagnetic valve armature, or valve plug, assumes the exact height above the valve’s orifice required to maintain the valve’s command flow (set point). The result is excellent resolution.