QSI 520c Guía de usuario descargar pdf (Pagina 18)

QSI 500 SERIES USER GUIDE

will rise by only a few degrees after a full

Liquid Heat Exchanger, see the Acce

night of imaging. For additional details on the

ssories section below.

Note: The Fans can usually be turned off when using the LHX. In fact, the fans

may actually decrease the cooling ability if the air is warmer than the liquid.

Caution: It is generally advised that only water be used in the LHX. Coolants

such as ethylene glycol and some solvents may damage the seals and gaskets.

How Much Cooling Is Enough

Good results can be obtained with the CCD cooled to -10ºC when taking modest length

exposures. This is easy to achieve with forced air cooling when the ambient air is at 25ºC

in QSI 500 Series cameras, dark current is reduced by half for

st 0.4% of the dark current at 26C. Cooling below -30ºC results in a

diminishing improvement as the noise from the dark current is outweighed by the intrinsic

(77ºF). For most CCDs used

every 6ºC drop in the temperature of the CCD. Cooling from 26C to -10ºC results in a 64-

fold decrease in CCD dark current. For more demanding imaging and longer exposures,

lower temperatures are desirable. Cooling the CCD another 12ºC to -22ºC lowers the dark

current further to ju

read noise of the CCD itself. The camera will actively prevent the CCD from being cooled

below -40ºC.

Fahrenheit -40F -20F 0F 20F 32F 40F 60F 80F

Celsius -40C -29C -18C -7C 0C 4C 16C 27C

Note: Refer to the specification sheets at the end of this Guide for the exact

cooling specifications for your particular camera model. Keep in mind that

ambient temperature changes, air movement, and even relative humidity can

affect the temperature that the camera can reach and maintain.

Note: The cooler is not designed to raise the temperature of the CCD above the

temperature of the camera body, i.e. it can not heat the CCD. If the ambient

temperature is -10ºC, the cooler can not bring the CCD temperature up to 0ºC.

When using forced-air cooling the body of

can be up to 12ºC warmer than the surrou

the camera and the window of the CCD chamber

nding ambient air temperature. By definition, the

camera will be above the dew point (or frost point) and condensation will not form. Whe

using the LHX there is the opportunity to drive the enclosure of the camera and the CCD

chamber window significantly below ambient temperature if the recirculating water is colder

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QSI 520c Guía de usuario Pagina 18