Amptek PC5 사용자 설명서 - 페이지 11

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filter is compensated for – in other words, the output HV should be independent of load

that the output of the filter, at the J2 or J5 connector, cannot be measured with a conventional DVM

(input impedance 10 M). A high impedance probe is required.

5.3

Thermoelectric Cooler Discussion

The control circuit for the thermoelectric cooler is shown in the schematic below. This circuit

maintains a fixed temperature rather than a fixed output voltage. A temperature sensor is located in

the detector hybrid. The conditioning circuitry generates an output of 10 mV/K (2.2 V at 220 K). This is

compared to the set point to generate the error signal.

Figure 7. Schematic for thermoelectric cooler supply circuit.

For use with a DP5, VR3 is not installed and the DAC controls the value. For use without a DP5, VR3

is installed (along with other components) and the DAC is disconnected. There exists a maximum

temperature differential which a given cooler can achieve. If the set point is lower than this, then the

supply will provide maximal cooling (with an output current limit) but the detector temperature is no

longer regulated. It will change as the system temperature changes.

A typical two‐stage cooler can generate an 85 °C ∆T. Example: If room temperature is 20 °C, then

the maximum cold temperature is ‐65 °C. It is vital that the detector temperature remain constant.

Therefore the set point must be set such that no matter what the ambient temperature reaches, the

detector temperature stay constant. Example: If room temperature is 40 °C the temperature set point

must be set such that this is regulated, so the coldest the detector can be set to is ‐45 °C. This means

that even at 20 °C room temperature the detector will be at ‐45 °C, but it will be constant from 20 to 40

°C.

The temperature sensor, inside the detector, is a 1N914. The forward voltage, at a fixed current, is

a function of temperature and is used to regulate the detector temperature. A typical calibration curve

can be found at www.amptek.com.

Note that PC5s earlier than Rev D0 (early 2013) take the feedback from before the output filter, so that

there will be some voltage drop across the 2.5Mfilterdepending on current.

Your

Products for

Supply

TEMPMON

TP17

Error

TP16

Amplifier

TEMPSET

Imagination

TEC

RC Filter

Power

Temperature

Conditioning

VR3

DAC

. Also note

Sensor