MPXM2102AS datasheet(541/670 Pages) MOTOROLA

541 / 670 page

3–395

Motorola Sensor Device Data

www.motorola.com/semiconductors

AN1950

Water Level Monitoring

By Michelle Clifford

Applications Engineer

Sensor Products Division

Tempe, AZ

INTRODUCTION

Many washing machines that are currently in production

use a mechanical sensor for water level detection.

Mechanical sensors work with discrete trip points that enable

water level detection only at those points. The purpose for this

reference design is to allow the user to evaluate a pressure

sensor for not only water level sensing to replace a

mechanical switch, but also for water flow measurement, leak

detection, and other solutions for smart appliances. This

system continuously monitors water level and water flow

using the temperature compensated MPXM2010GS pressure

sensor in the low cost MPAK package, a dual op–amp, and the

MC68HC908QT4, 8–pin microcontroller.

SYSTEM DESIGN

PRESSURE SENSOR

The Motorola Pressure sensor family has three levels of

integration – Uncompensated, Compensated and Integrated.

For this design, the MPXM2010GS compensated pressure

sensor was selected because it has both temperature

compensation and calibration circuitry on the silicon, allowing

a simpler yet more robust system circuit design. An integrated

pressure sensor, such as the MPXV5004G, is also a good

choice for the design eliminating the need for the amplification

circuitry.

The height of most washing machine tubs is 40cm,

therefore the water height range that this system will be

measuring is between 0–40cm.

This corresponds to a

pressure range of 0 – 4 kPa. Therefore, the MPXM2010GS

was selected for this system.

The sensor sensitivity is

2.5mV/kPa, with a full–scale span of 25mV at the supply

voltage of 10 Vdc. The full–scale output of the sensor changes

linearly with supply voltage, so a supply voltage of 5V will

return a full–scale span of 12.5 mV.

(Vs actual / Vs spec) x Vout full–scale spec = Vout full–scale

(5 V/ 10 V) x 25 mV = 12.5 mV

Since this application will only be utilizing 40% of the

pressure range, 0–4kPa, our maximum output voltage will be

40% of the full–scale span.

Vout FS x (Percent FS Range) = Vout max

12.5 mV x 40% = 5.0 mV

The package of the pressure sensor is a ported MPAK

package. This allows a tube to be connected to the sensor;

the tube is connected to the bottom of the tub. This isolates

the sensor from direct contact with the water. The small size,

and low cost are additional features that make this package a

perfect fit for this application.

Figure 1. MPXM2010GS/GST1

Case 1320A

MOTOROLA

SEMICONDUCTOR APPLICATION NOTE

REV 0

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

MPXM2102AS Datasheet(PDF) 541 Page - Motorola, Inc

MPXM2102AS Datasheet(HTML) 541 Page - Motorola, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL