Analogue and digital measurements in compact DIN rail module
Frequency and period measurements
Quadrature phase decoder channel pairs
Isolated 15/16 bit analogue channels
Relay output channels
High speed RS485 to 230KB (460KB)
Second local diagnostic serial interface
The 934S module provides three pairs of digital inputs for three quadrature phase decoder channels each with two phase inputs.
Four independently isolated analogue channels are included, with input range options. Each of these analogue channels has it’s own ADC running continuously. The technique used is continuous integration, which offers the best noise performance in real world conditions by using all the available signal instead of sampling the signal at discrete intervals. The primary integration period is 3.3mS. Typically, three measurements are averaged to present 100 samples per second per channel for example. Other Integration times can be programmed enabling measurements to be made with 50 or 60Hz mains rejection. These measurements then derive from a continuous integration over one mains period offering fast update rates but high mains based noise rejection. Different integration times can be programmed for each analogue channel.
Each analogue channel is fully independently isolated from all digital inputs and other analogue channels using solid-state transformer isolation. This eliminates ground loop effects and provides protection to the equipment in the event of faults or incorrect wiring of input connections. It also makes a fault on one channel much less likely to affect other channels.
Ten additional opto-isolated channels are provided for medium speed counting, low frequency, period, interval, RPM and digital status measurement are included. These channels support counting and frequency measurements to 1KHz .
The 934A also includes four fused relay outputs are provided as general purpose auxiliary outputs.
Complete measurement scans of all channels are typically completed at 100 scans per second. To maintain exact measurement intervals and to allow a host computer some variability in communication times, the measurements are efficiently packed into a First In First Out (FIFO) measurement buffer within each 936 module.
The 934 standard firmware supports normal use of the I/O facilities returning measurements efficiently to a host computer using a RS485 communications port.. The firmware has also been designed to be easily customised to specific application requirements.
As with other modules in the Alpha series, a local serial interface can be used to program and monitor operation locally independent of the communications on the RS485 network. This can be very convenient during installation or used later to diagnose application problems at the measurement site. Alternatively it could be used with a permanent local process display. Customised display output can be provided. All configuration settings are stored in secure non-volatile flash memory. .