PAS 9739/AI : 39 Channel Photodiode
and Dual ADC VME Analog Input Card
Links to printable product info:
The PAS 9739/AI is a VME based, thirty-nine channel, photodetector
and dual ADC, Analog Input Card. Each channel consists of a photodiode
driving the inputs of a pair of current to voltage conversion amplifiers.
The amplifiers have different gains and provide high and low sensitivity
outputs. The amplified outputs are digitized by a pair of twelve
bit, 500 KHz, Analog to Digital Converters (ADCs) and stored in
a memory array that is accessible by the VME bus.
Each ADC chip consists of two, 500KHz, twelve bit ADCs with a three
channel multiplexer connected to the input of each ADC. In normal
operation, the card simultaneously samples and converts the high
and low sensitivity signals associated with a given photodetector,
and stores the digitized data in the memory array. After completion
of the conversion, the card increments to the next channel and performs
a pair of conversions. This repeats continuously for the three channels
connected to each ADC.
Thirteen ADC chips are provided on this card, and they synchronously
scan their three input channels. The converted data is stored in
an array that is accessible by the VME bus while the card is scanning.
Data from the high and low sensitivity channels can be read with
a single 32 bit VME transfer. This approach provides data for all
channels with a maximum latency of six microseconds plus the VME
bus access time.
Calibration circuitry is provided that will inject known currents
into the front end amplifiers, when enabled with a control instruction.
The calibration feature is useful for verifying the functionality
of the input amplifiers and A to D converters.
Key Features
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Thirty-nine channel, photodetector and dual gain analog input card
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Dual gain amplifiers provide high and low sensitivity outputs for each photodiode
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Thirteen synchronously scanning ADC chips
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High and low sensitivity outputs of each channel are converted simultaneously
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High and low sensitivity data is available in a single 32 bit VME read
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Calibration signals are provided on every channel
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Thirty-two bit test register provided to verify the VME bus
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