MICS-5914 - AMPHENOL - Datasheet.Live

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This datasheet describes the use of the MiCS-5914. The

package and the mode of operation illustrated in this

document target the detection of ammonia (NH3).

FEATURES

• Low heater current

• Wide detection range

• Wide temperature range

• High sensitivit y

• Miniature dimensions

• High resistance to shocks and vibrations

OPERATING MODE

The recommended mode of operation is constant power.

The nominal power is PH = 66 mW. The resulting

temperature of the sensing layer is about 320 °C, in air at

approximately 20 °C.

Detection of the pollution gases is achieved by measuring

the sensing resistance of the sensor. The resistance

decreases in the presence of NH3.

SENSOR CONFIGURATION

The silicon gas sensor structure consists of an accurately

micro machined diaphragm with an embedded heating

resistor and the sensing layer on top.

The internal connections are shown below.

Pin Connection

A

B

C Rh1

D Rs1

E

F Rh2

G Rs2

H

J

K

Figure 1: MiCS-5914 configuration (bottom view)

MiCS-5914

NH3 Sensor

Rs: sensor resistance

Rh: heater resistance

POWER CIRCUIT EXAMPLE

As shown below, one external load resistor can be used to

power the heater with a single 5 V power supply.

Figure 2: MiCS-5914 with recommended supply circuit

(top view)

R1 is typically a E96 resistor at 93.1 Ω. This resistor is

necessary to obtain the right temperature on the heater

while using a single 5 V power supply. The resulting

voltages is typically VH = 2.2 V.

SENSOR CHARACTERISTICS

0.01

0.1

1

10

0.1 1 10

NH3 concentrat ion [ppm]

R

s

/R

0

Figure 4: Rs/R0 as a function of NH3 concentration at

40% RH and 25 °C, measured on an engineering test

bench

MEASUREMENT CIRCUIT EXAMPLE

As shown below, the sensitive resistance shall be read by

using a load resistor.

Figure 3: MiCS-5914 with measurement circuit (top

view)

The voltage measured on the load resistor is directly linked

to the resistance of the sensor. RLOAD must be 820 Ω at

the lowest in order not to damage the sensitive la yer.

ELECTRICAL CHARACTERISTICS

Rating Symbol Value/Range Unit

Maximum heater power dissip ation PH 88 mW

Maximum sensitive layer power dissipation PS 8 mW

Voltage supply Vsupply 4.9 / 5.1 V

Relative humidity range RH 5 / 95 %RH

Ambient operating temperature Tamb -30 / 85 °C

Storage temperature range Tsto -40 / 120 °C

Storage humidity range RHsto 5 / 95 %RH

OPERATING CONDITIONS

Parameter Symbol Typ Min Max Unit

Heating power PH 66 60 73 mW

Heating voltage VH 2.2 - - V

Heating current IH 30 - - mA

Heating resistance at nominal power RH 72 64 80 Ω

SENSITIVITY CHARACTERISTICS

Characteristic Symbol Typ Min Max Unit

NH3 detection range FS 0.1 100 ppm

Sensing resistance in air (see note 1) R0 - 10 1500

kΩ

Sensitivity NH3 1 ppm (see no te 2) S1 - 1.5 15 -

Notes:

1. Sensing resistance in air R0 is measured under c ontrolled ambient conditions, i.e. synth etic air at 23 ± 5 °C and 50 ± 10 %.

Sampling test.

2. Sensitiv ity NH3 1 ppm is defined as R S in air (R0) divided by RS at 1 ppm NH3. Test conditions are 2 3 ± 5 °C and 50 ± 10%

RH. Indicative values only, sampling test.

IMPORTANT PRECAUTIONS

Read the following instructions carefully before using the MiCS-5914 described in this document to avoid erroneous

readings and to prevent the device from permanent damage.

• The sensor must be reflow soldered in a neutral atmosphere, without soldering flux vapours.

• The sensor must not be exposed to high concentrations of organic solvents, silicone vapour or cigarette-smoke in order to

avoid poisoning the sensitive layer.

• Heater voltages above the specifie d maximum rating will destroy the sensor due to overheating.

• This sensor is to be placed in a filtered p acka ge that protects it against water and dust projections.

• e2v strongly recommends using ESD protect ion equipment to handle the sensor.

• For any additional questions, contact e2v.

PACKAGE OUTLINE DIMENSIONS

The package is compatible with SMD assembly process.

SOLDERING PADS GEOMETRY

PACKAGING TAPE AND REEL FOR EXPEDITION

The sensors are placed in a carrier tape. The dimensions of the cavity are 5.5 x 7.5 x 2.55 mm (the tolerance is +/- 0.2 mm).

The outside diameter of t he r eel is either 178 + /- 1 mm (for a ma ximum of 700 se nsors) or 330 + 0.25 / -4 mm (for a m aximum of

2000 sensors).

e2v semiconductor gas sensors are well suited for leak detection and applications requiring limited accuracy. Their use for absolute gas concentration detection is

more complicated because they typically require temperature compensation, calibration, and sometimes as well, humidity compensation. Their base resistance in

clean air and their sensitivity can vary overtime depending on the environment they are in. This effect must be taken into account for any application development

(1108-1.0).