CAMAC 24-Bit Sigma-Delta ADC Module

The 3596 is a single-width CAMAC module that functions as either a single-scan or continuously active 16-channel Sigma-Delta ADC.

Sigma-Delta conversion is a technique which attains its very high accuracy by digitally decimating/filtering the output of a fast, single-bit converter. This eliminates the need for expensive tracking filter, sample/hold, and gain functions allowing a simple ADC-per-channel structure. This further eliminates the need to multiplex inputs to a common ADC and thereby reduces crosstalk effects to negligible levels.

Another important consequence of the digital filtering is that filter notches are produced which can be made to coincide with 60 Hz (or 50 Hz) power line frequencies and their harmonics. Thus, even in environments with severe signal corruption due to power line noise, very good results are possible.

CAMAC 24-Bit Sigma-Delta ADC Module: 3596

3596 Data Sheet

Supporting Chassis

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The 3596 module provides for independently selectable post-gains of 1 to 128 on differentially-received inputs which accept up to 10 volts fullscale. A common sampling rate should be chosen for all channels and may range from 9.76 Hz to 1.028 kHz. These frequencies also define the first notch in the build-in lowpass tracking filters. The -3dB bandwidth is consequently always 0.262 times the selected sampling rate. The effective resolution of each channel is derated by increased gain and sampling rate, and ranges from 19-bits at a gain of one and a 10 Hz rate to 8-bits at a gain of 128 and a 1 kHz rate. For all gains at rates of 100 Hz and below, resolution is at least 15-bits. In addition, a channel-by-channel programmable pre-gain of 100 may be selected with only minimal reduction of effective resolution.

When a Single-Scan operation is triggered, a single conversion cycle takes place and one sample point for each channel recoded. The channels are first synchronized so that these samples correspond to the same point in time. This synchronization process causes the data to remain invalid for four sample intervals of the selected sample rate. When all 16 channel samples have been recorded after this interval, a LAM Request signal, if enabled, is issued to indicate that the channels are ready for read-out. Alternatively, the LAM Status condition may be polled by waiting for a valid "Q" response to an F(27)•A(0) CAMAC command to indicate that data is available. In addition to LAM, a TTL "DATA RDY" trigger output is provided on the front panel which may be used to trigger a CAMAC list-processing device like the KineticSystems Model 3982 module.

The 3596 module provides for two mechanisms of offset and gain calibration. A self-calibration mode uses a mid-scale (0 volts) and positive full-scale reference internal to each channel's Sigma-Delta converter to calculate offset and gain for that converter. Alternatively, a system calibration mode may be selected which connects mid and full-scale voltages through the entire front-end circuitry of each channel for greater absolute accuracy. This method uses the module's analog ground as the mid-scale voltage and an external full-scale reference through the REF IN front-panel, two-conductor LEMO connector.

The LAM and Overwrite Status commands may be used to avoid rereading "stale" data and to indicate if samples were missed (overwritten before being read). A full complement of clock and trigger inputs and outputs are available to allow synchronous data-taking over multiple 3596 modules.

CAMAC Module Features

  • 16 Channels 24-Bit Data Fields
  • Up to 19-Bits Single-Shot Resolution or More with
    Sampling Averaging
  • Automatic Tracking Filtering
    (-3dB at 0.262 Sample Rate)
  • Channel-by-Channel Programmable Pre-Gain (1 or 100)
  • Channel-by-Channel Programmable Post-Gain (1 through 128)
  • Continuous Scan Mode at 9.76 Hz to 1.028 kHz Sampling Rates
    per Channel
  • Single-Scan Mode Through Synchronizing Front-Panel
    Trigger In & Out or CAMAC Command F(25)•A(0) or
    CAMAC "C" Clear Operation
  • Two Calibration Modes: Internal Zero/Full-Scale References
    or External (Front-Panel LEMO) Full-Scale Reference

CAMAC Module Ordering Information

3596 Products and Part Numbers
16 Channels, 24-bit Sigma-Delta ADC 3596-Z1A
16 Channels, 24-bit Sigma-Delta ADC,
with Sensor Power