Alpha 636 Isolated Digital and Analogue I/P Processor

€ - POA


What is the Alpha 636 Isolated Digital and Analogue I/P Processor?
The Alpha 636 module provides six digital input channels for counting, frequency or status measurements. Counting and frequency measurements on these channels support input rates 15Khz.

The first four channels can also be configured in pairs as one or two quadrature phase decoder channels for rotary and linear and displacement sensors. 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. Other integration times can be programmed for each channel, enabling measurements to be made with high 50 or 60Hz mains interference rejection and fast update rates.

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 an overload of on one channel much less likely to affect other channels.

Four additional lower speed op-to-isolated channels are provided for count, low frequency, period interval, rpm and digital status measurement. These channels support counting and frequency measurements to 1KHz, and period measurement to a resolution of 1mS. Multiple period measurements can provided a resolution down to 10uS.

Six isolated and fused relay outputs are provided as general purpose outputs. Complete measurement scans of all channels are typically completed at 100 scans per second or higher.

To maintain accurate 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 with each 636 module.

The Alpha 636 standard firmware supports normal use of the I/O facilities returning measurements efficiently to a host computer using a RS485 communications port.

Up to 99 modules can be connected to a single RS485 network. The firmware can be easily customized for specific application requirements.

As with other modules in the Alpha series, a local serial interface can be used to program and monitor operating locally independent of the communications on the RS485 network.

This can be very convenient during installation or sued later to diagnose application problems at the measurement site.

Alternatively, it could be used with a permanent local process display. Customized display output can be provided. All configuration settings are stored in secure non-volatile flash memory.


  • 20 Channels of 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.


Frequency, Counter, Status Channels

Number of channels: 6

Input threshold: 3.5V

Input operating range: 3.5 – 12V

Input count rate: 15KHz

Isolation: Each channel is individually isolated.

Relay Output Channels

Number of relay outputs: 6

Relay output rating: 48V 2A Fused

Minimum output load (wetting): 12V/10mA

Isolation: Each channel is an isolated contact pair.

Phase Decoder Channels

Number of phase decoder inputs: 2 Pairs (using the 4 freq channels)

Input threshold: 3.5V

Input operating range: 3.5 – 12V

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

Input count rate: 15KHz

Minimum pulse width/gap: 20uS

Isolation: Each channel is individually isolated

Time base accuracy: Typically 0.02%

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: 60dB

50Hz: 20mS integration time.

60Hz: 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

636 – Power < 4.5W


RS485 Communications Interface: Baud rates 38K4 to 230KB supported (460KB is available for some applications)

Number of Alphamet modules per link: 99

Measurement throughput of link: 10,000/sec (depends on application) 2000-4000/module type

Local RS232 Interface: Baud rates to 38K4 supported.

Status, Counter, Low Frequency, Period Channels


Alpha Server Brochure: [Brochure]

Alpha OPC Brochure: [OPC Brochure]

Alpha 636 Datasheet: [Datasheet]