ZTP315 datasheet(2/4 Pages) ETC2

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Application

Considerations

Specific Detectivity

The NEP is convenient for predicting the maximum

power a given system can detect, but it has some

undesirable features:

•

A good thermopile detector will have a small

NEP.

•

The thermopile detectors of different sizes will

have different NEPs.

So we cannot say, in general, what a good NEP

should be, unless we specify the size of thermopile

detector.

Detectivity has been introduced to include device

noise and sensitivity simultaneously. It is usually

normalized with respect to detector size and noise

bandwidth, and the resulting specific detectivity,

D*, is defined by:

A large D* is good, and for a given environment all

good detectors should have almost the same D*.

Noise

The thermopile detector noise is another important

factor determining the detector performance.

There are many noise sources in a thermopile

detector. A fundamental noise is caused by actual

temperature fluctuations.

A theoretical limit of thermopile sensitivity will be

determined when this noise is at its minimum.

In this thermopile detector, Johnson noise of these

many noise sources is a predominant electrical

noise source. Since the device impedance for a

typical thermopile detector is mainly resistive,

the Johnson noise for a detector having a device

resistance R is:

where B is the noise bandwidth. At low frequency,

flicker noise originating from contacts or other

sources may be dominants, and, depending

upon the sensing materials, shot noise may also

be involved. Typically, Johnson noise is the most

important of these electrical noise sources for

most thermopile detectors.

Package

Our thermopile detector is packaged with silicon

filter and thermistor as shown below. We are

supplying TO-5 package and TO-46 package as

the standard type , but on request, other package

types are also available.

(1) Thermistor for the compensation of

an environment temperature

According to the variation of an environment

temperature, the output of thermopile

detector is also varying. It is therefore

need to compensate this temperature

performance of thermopile detector. Our

thermopile detectors are using a thermistor

for the compensation of an environment

temperature, and we have also a variety of

thermistors enough for pursuing customer`s

need.

(2) Windows Filter

In order to improve the thermopile detector

performance, it isalso a very important

factor to select suitable filter for a given

application. We are basically using a

broadband-silicon filter of which the

transmittance is 6-13um.

But when there is an application for

an optical system, the preparation of

proper filter specifications is also of prime

importance for the optimum performance.

Therefore we are available for many typical

infrared filters -not only a broad band pass

filters (BBP) but also a narrow band pass

filters (NBP).

The following specifications will assist an

engineer who designs the optical system.

Detector Packaging

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