Microtechnology Project Report

Report for Laboratory work on: OMRON D6F Flow Sensor Name: Dylan Hughes EGT-280: Introduction to Microtechnology

Cover Page

Report #1

Name of Report: MEMS Project Report

Your Name: Dylan Hughes

Submitted to:

Dr. S.M. Allameh

In partial fulfillment of the requirements for

EGT-280: Introduction to Microtechnology

Department of Physics and Geology Northern Kentucky University

June 2017

Report for Laboratory work on: OMRON D6F Flow Sensor Name: Dylan Hughes EGT-280: Introduction to Microtechnology

Name of Report: MEMS Project Report By: Dylan Hughes

Abstract:

This project report discusses the MEMS selection process, initial setup and wiring of the MEMS device, problems/difficulties encountered, and internal inspection and functionality of an OMRON D6F-P0010A2 MEMS Mass Flow Sensor. The internal inspection reveals the functionality, principles, and theories that govern operation of a thermal mass flow sensor. Selection criteria for the MEMS device is also discussed, as well as the importance of having the correct connections and equipment to power and communicate with a micro device.

Introduction:

The OMRON D6F-P series of flow sensors offers compact size, excellent accuracy, and a dust segregation system that allows the flow sensor to be used in dirty, dusty environments. Because of the micro device’s size, it can be used in very tight, space-critical applications. Mass flow sensors similar to the D6F-P line are being used in many applications today. The most common use for flow sensors is within the automotive industry. Flow sensors are used to monitor the amount of air flowing through the intake system and into the combustion chamber. The onboard computer then uses that data, along with several other sensor’s data, to calculate the proper air-to-fuel ratio for the current running conditions. Flow sensors are also used to control engine idle, monitor recirculatory exhaust systems, and keep the interior of the vehicle cool and comfortable. Flow sensors have also seen an increase use within the HVAC industry. Because of OMRON’s dust segregation system, the D6F line of MEMS flow sensors can be used to monitor air in nasty environments. Micro flow sensors typically have a maximum flow rate of 1.0 LPM. The low flow rate allows the sensor to be placed within a bypass system. The flow rate of the bypass air is then proportional to the flow rate for the entire system.

Selection Process:

The OMRON D6F-P0010A2 sensor was selected for several reasons. Firstly, because of my experience with various flow sensors on-the-job and in automotive repair work. I have worked with several different flow sensors but have never had the opportunity to open one and discover how it works. Being so familiar with their functionality and importance, especially within the automotive industry, I was very excited to see the internal workings. The second reason for choosing the D6F flow sensor was cost and proper documentation. OMRON was easy to contact and provided several datasheets with specifications for input voltage, output voltage, operating pressure, and detailed wiring schematics. I have never purchased from OMRON in the past, but because of their customer support and eagerness to help, I will consider their products in the future. The final reason for choosing the D6F-P flow sensor was ease of setup and availability of an appropriate power supply.

Report for Laboratory work on: OMRON D6F Flow Sensor Name: Dylan Hughes EGT-280: Introduction to Microtechnology

Initial Setup:

The initial setup of the MEMS device was challenging because the device was not purchased with the appropriate connector. Because of the device’s size it was impossible to establish a firm connection without the correct plug. After purchasing and receiving the correct connector, along with OMRON’s provided wiring diagram, setup of the MEMS device was very straight forward. An Acopian regulated power supply was used to provide 6.0 vDC to the MEMS device. A digital volt meter was connected to the output terminal and ground terminal of the MEMS device to provide voltage monitoring proportional to the mass flow rate. Air was supplied to the MEMS device using a small air compressor and inline pressure regulator. The air outlet was vented to the atmosphere. Below is a picture of the initial setup of the MEMS device.

Problems: As mentioned before, the OMRON sensor did not come with a connection cable – it was an additional accessory that I chose not to order. I have never worked with a micro device before and did not expect the connection terminals to be so small. Once I was able to successfully power the device, I then ran into problems with the accuracy of the air pressure regulator. At pressures below 10 PSI the pressure regulator did not display reasonable measurements. D6F-P flow sensors are rated to withstand pressures of 7 PSI, so voltage-to-

Report for Laboratory work on: OMRON D6F Flow Sensor Name: Dylan Hughes EGT-280: Introduction to Microtechnology

pressure correlations were not possible. However, the output voltage characteristics of the D6F-P0010A2 were found on the D6F-P datasheet provided by OMRON, and the results are shown in the following chart:

Internal Inspection: I found the internal workings of the MEMS device to be very intriguing and “relatively” easy to understand after watching OMRON’s MEMS Sensor Product Technology Module. The module discussed and explained every aspect of the MEMS Flow Chip, the internal flow path and dust segregation system, and the concept behind using thermopiles and heaters to measure the mass flow rate. After cutting the security sticker along the top of the device, I was able to remove the back cover using a small flathead screwdriver. The top of the micro device was then visible. Below is a picture with the back cover removed.

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D6F-P0010A2 Voltage Characteristics

Flow Rate (L/min)

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Report for Laboratory work on: OMRON D6F Flow Sensor Name: Dylan Hughes EGT-280: Introduction to Microtechnology

I was then able to remove the circuit module, which revealed the upper air flow path and the MEMS Flow Chip. The upper flow path is the only path monitored by the flow chip.

Report for Laboratory work on: OMRON D6F Flow Sensor Name: Dylan Hughes EGT-280: Introduction to Microtechnology

The dust segregation component in the middle of the housing was then removed to reveal the lower flow path. The air flow through the lower path is not monitored by the MEMS flow chip, but the measurement through the upper flow path is proportional to the total mass flow rate. Centrifugal force keeps dust and particles in the lower flow path and out of the upper flow path. This design ensures air through the micro flow chip is clean and particle free.

Report for Laboratory work on: OMRON D6F Flow Sensor Name: Dylan Hughes EGT-280: Introduction to Microtechnology

I then used a strong magnifying glass to examine the MEMS Flow Chip. The D6F-P flow sensor operates under the principle of a temperature differential. Two thermopiles are used to monitor the air temperature of incoming and outgoing air through the flow chip. A heating element placed between the thermopiles creates a temperature difference that can be seen between the two thermopiles. This temperature differential creates a voltage that is proportional to the mass flow rate of the air flowing through the flow chip. Below is a close-up image of the MEMS Flow Chip.

Conclusion: MEMS Mass Flow Sensors are being used in more and more applications because of their durability, repeatability, and affordability. Micro flow sensors can be used to monitor a proportional amount of air flow which allows them to be installed in small, out-of-the-way areas. After purchasing, experimenting with, and inspecting the micro device, I now have a greater understanding of the complexities of MEMS devices, as well as the operating principles governing a thermal flow sensor.

Report for Laboratory work on: OMRON D6F Flow Sensor Name: Dylan Hughes EGT-280: Introduction to Microtechnology

Student ID and disassembled MEMS device for reference and credibility.