Product Description

The ADC 1232-2 is a single-width, differential 32-channel, 12-bit ADC module with programmable gain and a wide capability of input voltage, filtering and scanning speed. It can operate stand-alone or as part of our Flying Capacitor Scanning System. Other units in the series (-1, -8) are very similar but have different ranges.

Introduction

Operation of this unit in 'High Range' or 'Low Range' (typically 'volts' or 'tens of mV' full scale) is selected by on-board plug-socket links: within each range one of 3 sub-ranges is selected either by link or by software. Other ranges than standard may be chosen by simply changing some precision resistors.

Technical Details

This versatile module has 32 operational plus-socket links, as shown below. Thus, for example, these links can be used to select the ranges given in the table below, where the effect of adding on-board wire link or changing 5 R-values is also shown. The arrangement of the sub-range differential amplifier, linkset High/Low gain and 0.8/8.0 kHz filter amplifiers is shown in Fig. 1 together with a schematic of the first of these, which has a gain of 1 + 2 x/y. For the standard resistor value of A = R24, R25 = 2K; B = R22, R23 = 250; C =500; closing contracts 1, 2 or 3 by link (link 1, 1 + 2 or 1+ 3) or software (see below) gives gains of 1, 5 or 10, leading to High-range full-scale inputs of 10V, 2V or 1V respectively.

Operation

The unit selects each point in turn, closes the MOS switcher and waits the settling time: a 'Start' command is then sent to the ADC chip. When conversion is done the value is places in the 32-chan store, MOS address incremented and the sequence continued. Any point can be read via CAMAC at any time during scanning, which can be continuous updating or one scan of all 32 channels: data is in 2's complement. The unit has a 4-pin LEMO trigger/busy connector, which accepts a 100mS TTL 'low' pulse to initiate a full 32-channel single scan if Link 4 is open, and which puts out a TTL 'low' ' busy' level while scanning is in progress, for hand-shaking with mux units such as the MXD5121.

Performance

The basic ADC chip, DATEL HY112 BC or equivalent, has a conversion time of about 11 microseconds, but because of settling time needed for 12-bit accuracy, the four link-set scanning rates for this unit are much slower at 800Hz (essential for Low range), 1.6Hz, 3.2Hz and 8kHz.

Mechanical

Single-width CAMAC unit fitted with hard-anodised side-screens, designed to operate in ambient temperature range of 10?C to 45?C. Power consumption typically:

The two 16-channel differential inputs each come in via a normal 37-way 'D' series connector.

The other characteristics are:

Instruction Set

Reading 2's complement data on bits 1-12 by F(0) or F(1) shows the sign bit (12) repeated on bits 13 - 16, and if the sub-range is set by links 1, 2 or 3 then the chosen one is chosen by 1, 2, 3 = 00,01,10 on bits 24, 23. Sub-range may be software set with links 1, 2, 3 open by writing to the sub-range register for each channel by F(17) A(0) with the word:

X = don't care

Z clears internal lock-up possibly caused by serious disturbance of backplane volts.
C, I No Effect.

Other Units

The original unit in this, the ADC 1232, is no longer available, but the next one, ADC 1232-1, is: it is much like the -2 but only has a coax LEMO front panel-trigger (TTL pulled up via 4k7) with no 'ADC busy' signal, and the main high range unipolar values at 1V, 5V, 10V rather than the 1V, 2V, 10V of the -2.

A current unit in the series particularly designed for Power Station use is even closer to the -2 than is the -1, the only difference being the corresponding range values are; 1V, 1.5V, 10V: the middle range used with our Flying Capacitor Scanner, which had a built-in gain of 50, gives a low range of 0-30mV which was wanted for their thermocouples.

The trigger/busy connector on the front panel is a 4-pin LEMO:

Two red LEDs are provided: one 'N' line, stretched to 25mS, and one 'Scanner running'.

Our policy is one of continuous product development and the right is reserved to supply equipment which may vary slightly from that described.