The Microlink 3000 Series offers a full range of analogue-to-digital converters for general purpose data acquisition.
One of the 304x modules is used within the Microlink 3000 frame whenever analogue signals are to be digitised. They are always used with one or more of the analogue input modules. These pre-condition and scale the input, and control which of the multiple inputs is connected to the A-D converter.
There are 4 modules in the 304x range. Which you choose depends on the speed and precision you require.
The 3042 gives 16-bit A-D conversion, dividing the full scale range into 64 K steps. (For more details of resolution and dividing the full scale range, see our A-D tutorial.) Because the analogue input modules of the Microlink system all have adjustable gain ranges, the 3042 is normally specified only when the signal to be captured has a very wide dynamic range, or the purpose of the measurement is to examine very small fluctuations in the value of a large DC signal.
The 16-bit number represents a signed integer, ie a number in the range -32768 to +32767. It makes sense then to use the analogue input modules in bipolar mode so that 0 V gives a 0 A-D reading. Don't use the higher gain ranges of the analogue input module with the 3042, as it will then attempt to resolve the internal noise of the amplifier giving fluctuating readings.
A-D resolution 16-bits Samples per second 40 000 Max linearity error ±0.006% Sample and hold acquisition time <10 usec Conversion time 15 usec
This module is similar to the 3041 in that it is a buffered A-D converter. It has greater resolution however, being a 16-bit converter like the 3042.
A-D resolution 16-bits Samples per second 40 000 Max linearity error ±0.006% Sample and hold acquisition time <10 usec Conversion time 15 usec FIFO buffer memory size 16 K
The 3044 uses a dual-slope integrating converter, which means the module is suitable for relatively slow sampling. The throughput of the 3044 is up to 12.5 samples per second, each sample being based on an integration of the signal over a period of 20 msec. This covers one complete 50 Hz cycle, so the 3044 is particularly useful when signals are contaminated with mains (or line) frequency pick-up, or higher frequency noise. The 3044 is the converter of choice for slow data logging from transducers such as thermocouples, or in electrically noisy environments.
A-D resolution 13-bits Samples per second 12.5 Max linearity error ±0.0122% Conversion time 80 msec
This module is similar to the 3044 but has 16-bit resolution and can digitise signals at up to 40 samples per second.
A-D resolution 13-bits Samples per second 40 Max linearity error ±0.002% Conversion time 23 msec
The analogue input facilities of the Microlink can be used in 2 modes. Systems without a 3070 module, or with the 3070 disabled, take single samples on demand. The computer addresses one of the analogue input modules, which then connects its signal to the 304x. A single conversion is performed and the digitised data passed to the computer. In this mode, sampling is controlled directly by software. When a 3070 module is used, the channels which are to be digitised are selected before data collection begins. The 3070 is then programmed to multiplex the selected inputs and take samples at precise time intervals. When collection begins the selected inputs are connected in turn to a 304x which digitises the signals. All the 304x modules can be used in high speed mode, apart from the 3044 and 3045.
For more details on analogue-to-digital converters and the Microlink 3000 system: