Alpha 631 Counter, Phase, Status Input and Digital Output Module

€ - POA



What is the Alpha 631 Counter, Phase, Status Input and Digital Output Module?
The Alpha 631 module provides six digital inputs for counting, frequency or status measurements. Counting and frequency measurements on these channels support inputs to 15Khz. These six channels can also be configured as three quadrature phase decoder channels, each with two-phase inputs.

Four additional op-to-isolated channels for medium speed counting, low frequency and digital status measurements are included. Contact de-bounce filters can be enabled on these channels.

Counting rates up to 1000 per second on each channel are available. Ten isolated and fused relay outputs are provided as general purpose outputs. Specific autonomous operation can be programmed by Alpha Metrology for custom applications.

An RS485 multi-drop interface is provided for normal operation with other Alpha series modules and a host computer. It can operate at speeds up to 230KB, with cable lengths of up to 1.2Km.

As with most 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. Customized display output can be provided. All programming can be stored in secure non-volatile flash memory.



  • Counting, Phase, Status and frequency in compact DIN rail module.
  • Frequency measurements
  • Phase decoder channel pairs.
  • Isolated Relay output channels.
  • Second local diagnostic serial interfaces.
  • High speed comms 230KB (460KB)


Frequency Counter Status Channels

Number of channels: 6

Input threshold: 3.5V

Isolation: Each channel is individually isolated.

Input operating range: 3.5 – 12V

Input count rate: 15Khz

Time base accuracy typically: 0.03%

Status Led’s

Colour: Red

Function: Power, RS485 Communications, RS232 communications

Channel 1-20 input-status level present.

Phase Decoder Channel’s

Number of phase decoder inputs: 3 pairs (using 6 frequency channels)

Input threshold: 3.5V

Input operating range: 3.5 – 12V

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

Third channel operates at 1 count per two pulses.

Input count rate: 15Khz

Minimum pulse width/gap: 10uS

Isolation: Each channel is individually isolated.

Module Dimensions

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

Weight: 0.6Kg

Status Counter Channels 

Number of status channels per module: Additional 4

Measurement functions: Status counting

Max count rate: 1000/sec each channel (4 channels)

Input threshold: 4V

Input operating range: 4-24V

Isolation: Each channel is individually isolated.

Update rate-counters or status function: 1000/sec 4 channels, 100/sec 6 channels.


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

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

Local RS232 Interface: Baud rates to 38K4 supported.


Software: no internet access required.


-20°C to 60°C ambient.

0 – 90%RH

Relay Output Channels

Number of relay outputs: 10

Relay output rating: 48V 2A Fused.

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

Isolation: Each channel is an isolated contact pair.

Power Requirements

12 – 36V DC OR 24V AC

631 – Power < 6V



Alpha Server Brochure: [Brochure]

Alpha OPC Brochure: [OPC Brochure]

Alpha 631 Datasheet: [Datasheet]