Alpha 934S Isolated Digital and Analogue I/P Processor

€ - POA


What is the Alpha 934S Isolated Digital and Analogue I/P Processor?
The Alpha 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 op-to-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 636 module.

The Alpha 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 customized to specific application requirements.


  • 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 auxiliary channels (934A)
  • Second local diagnostic serial interface
  • High speed comms 230KB (460KB)


Alpha 934S Specification Details

Phase decoder channels:

Number of phase decoder inputs: 3 pairs

Input threshold: 3.5V

Input operating range: 3.5V – 12V

Resolution: The 2 pairs offer discrimination of each edge resolving 4 counts per pulse pair.

Input count rate: 15Khz

Minimum pulse width/gap: 10uS

Isolation: Each channel is individually isolated.

Time base accuracy Typically: 0.02%

Analogue Input Channel

Number of channels per unit: 4

Input ranges: 0-2V (standard) 4-20mA (build option) 0-10V(build option)

Each channel can be specified separately:

Isolation: Each channel is individually isolated.

Resolution: 15bits (300/sec) – 16 bits (slower rates)

Programmable measurement rates: 300, 150, 100, 50-60, 10/sec for each channel – individually.

Status LED’s

Colour: Red



RS485 Communications

RS232 Communications

Channel 1-6,11-14

Status level status of output channels.


2 part high quality rising cage clamp screw terminal.

Module Dimensions

Dimensions: 180 x 120 x 65mm, DIN rail mounting.

Weight: 0.6Kg


Software: No internet access required.


-20 to 60°C ambient.

0 – 90% RH

Analogue Input Channels

Number of status channels per unit: 4

Input ranges: 0-2V(standard), 4-20mA (build option), 0-10V (build option).

Isolation: Each channel is individually isolated.

Resolution: 15 bits(300/sec) – 16 bits (slower rates)

Programmable measurement rates: 300, 150, 100, 50-60, 10/sec for each channel- individually.

Base integration time – each measurement: 3.3mS

Selectable true integration times: 3.3mS, 10mS, 16.67-20mS, 100mS

Mains rejection – Can be achieved by averaging consecutive measurements:

50Hz: 6 measurements – 20mS integration time.

60Hz: 5 measurements – 16.67mS integration time

Accuracy: 2V range +/- 0.02% reading +/- 0.02% of range at 23°C

Temperature coefficient: Typically 25ppm/°C

Power Requirements

12 – 36V DC or 24V AC: 934A Power < 4W, 934S Power <3W

Specifications subject to change without notice – correct at time of publication

Issue 1.02 DS934A01 Refers to 0.52 firmware release.

Status, Counter, Low Frequency, Period Channels

Number of status channels per module: 10

Number of period measuring channels: 6 or above 10

Measurement functions: Status, counting, frequency period, interval RPM

Max count rate: 100/sec each channel (All 4 channels)

Input threshold: 4V

Input operating range: 4 – 24V

Isolation: Each channel is individually isolated

Update rate – counters or status function: 100/sec 4 channels

Period resolution: 1mS-Single Period

Multiple period measurements: Up to 100 periods (60 secs total)

Effective resolution: Down to 10uS


Alpha Server Brochure: [Brochure]

Alpha OPC Brochure: [OPC Brochure]

Alpha 934S  Datasheet: [Datasheet]