Doc: UM0520
Issue: 3.0
Date: 07/01/2002
Page: 2/9
Author: PJM
1. INTRODUCTION
This unit is a high speed Analogue to Digital converter module with up to four
inputs, each with its own 12 Bit ADC chip and all capable of performing concurrent
conversions in as little as 10 microseconds. Each input is fitted with a sample-
and-hold amplifier with a settling time of one microsecond, whose gain can be
switched under Dataway control (to special order - see ADC521 below) to cater for
input ranges down to 500mV without significant drift errors. A comparator can also
be fitted as an optional extra, which when loaded with a 12 bit binary value from
the dataway performs a comparison with the output of channel 1 (Subaddress 0)
every time a conversion is completed, whereupon it can stop, or carry on
performing conversions depending on the state of "Greater than" or "Less than"
flags, allowing experiments like stress/strain plotting to be achieved very
easily. The "Fast" version of this unit, the ADC520F has a conversion time of 15
microseconds, a slightly slower standard version is available, with a maximum
conversion time of 25uS, as well as an even faster version ("EF" type) with a
conversion time of 10uS.
The ADC 521 is a variant of the ADC 520 which has analogue switches for each
channel to permit the gain of the Sample-and-Hold amplifier to be changed in a
"times 1" "times N" fashion, the value of N being chosen by the customer up to a
value of 50. See also section 6.
A Differential Input variant is also offered, where the input sample-and-hold
amplifiers are modified to take the difference between the two input lines from
two-pole front panel LEMO sockets. This type is selected by a suffix 'M'.
