Mass Air Flow Sensor                                                                  home

Quality / Development

DESCRIPTION

An Automotive OEM Parts Supplier required a complete system designed for conducting quality airflow calibrations or measurements on Throttle Chamber and Mass Air Flow Units. The Test System had to be flexible in design to accommodate both the different types of units to be tested, as well as the ability to perform a wide variety of types of tests on each Unit Under Test (UUT). This included the ability to interface and interact with each UUT beyond the basic requirement of “flowing” the UUT. The workstation would need to power, communicate and/or control each Unit-Under-Test (UUT) while concurrently setting mass flow points. Accuracy and repeatability were also critical elements in the design of the Test System.
SYSTEM REQUIREMENTS

» Vacuum Flow at Nominal Flow Rates ranging from .5 to 1540 kgs/hr.
» Unit Under Test (UUT) Control, Power Cycling, Communication and Programming Capabilities
» Part Fixturing, including air flow inlet and exit tubes
» Mechanical/Electrical/Pneumatic mating connector(s) and UUT actuators
» Expandable and Flexible Data Acquisition and Control sub-system
» Expandable Air-Flow metering system and Instrumentation
» User-friendly Test System Controller Software for Operator, Maintenance and Engineering personnel
SOLUTION

This workstation presented several challenges to the FLOW SYSTEMS Design Team. The “Flexibility” needed to test completely different UUTs over a wide variety of tests required that a modular Test Stand be designed that could be reconfigured quickly and easily by the operating personnel. FLOW SYSTEMS responded by designing a general-purpose flow stand with modular UUT fixturing to cover the wide range of functional testing required of this workstation.

FLOW SYSTEMS designed and manufactured a Test System that was built around a stand-alone airflow metering sonic nozzle chamber. The Sonic Nozzle Chamber is actually two chambers connected along a common plenum. The larger chamber houses a binary set of thirteen (13) Sonic Nozzles (Critical Flow Venturis). Three additional smaller nozzles are housed in a separate, smaller chamber. The smaller chamber greatly reduces the system volume allowing for finer flow control in very low flow testing. The Test System controller uses the current ambient conditions and a desired flow rate as inputs to compute the required nozzle pattern to set and then to open the nozzles. 

A series of functionally modular carts were designed and manufactured that either attach directly to the stand-alone flow meter, or work in conjunction with other carts. Each cart contains the necessary fixturing and electrical/mechanical/pneumatic connections required for assembly into a fully functional test system. A series of custom UUT hardware actuators were developed for each cart using Commercial Off-The-Shelf (COTS) equipment. Software was used to fully integrate each of the hardware components into a fully functional test system. Each cart is described below.

Mass Air Flow Sensors (MAFS) Carts: The MAFS come directly off the manufacturing line for QA checks or are units in pre-production development. One cart is designed to flow the MAFS at ambient (room) conditions at mass flows from .5 to 1540 kgs/hr. The second cart is designed to flow the MAFS at temperatures ranging from ambient to 80 C (176 F), and flow rates up to 250 kg/hr. The heated air is cooled immediately prior to entering the QAW airflow chamber to avoid measurement errors. The QAW test stand includes the necessary communication, programming and instrumentation hardware necessary to perform all UUT functional test requirements. The workstation included a Precision Dual Output Power Supply for powering the UUT. An 8½ digit multimeter was also integrated into the test system for reading output voltages from the UUT at various flowrates.

Throttle Chamber (T/C) Cart: This cart is used to perform a variety of functional tests on Throttle Chambers. One test is the Shaft Torque Test. This test measures the torque required to open and close the butterfly valve from zero valve angle to wide open throttle and closed again. The cart also allows for measuring flow rates through a throttle chamber by flowing a temperature-controlled mixture of ethylene-glycol and water through the UUT. The ethylene- glycol mixture temperature is typically set at –30, 25 or 65 degrees Celsius during testing. The cart also is capable of performing a variety of general flow tests on each UUT.

As with all FLOW SYSTEMS' Test System designs, the Test System controller, data acquisition and control subsystems, and all instrumentation are standard, readily available Commercial Off-The-Shelf (COTS) items. This ensures that servicing or replacement of any item can be achieved in a timely manner, providing for a high-availability for the Test System. This includes all of the UUT related instrumentation that was explicitly specified by the customer

SOFTWARE OPERATOR INTERFACE 

The following image illustrates one of the operator interfaces of the test system.

 

SPECIFICATIONS

» Flow Elements: Sixteen (16) Critical Flow Venturis (Sonic Nozzles) arrays in two separate chambers
» Flow Range:     .5 to 1540 kgs/hr. @ 14.2 psia, 70°F
» Accuracy:        +/- 0.17 % of reading, traceable to NIST standards
» Repeatability:   +/-0.08 % or better 


SYSTEM LAYOUT

The following diagram illustrates the physical layout of the test system.

Click to view enlarged image

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