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Alpha 614

Alpha 614 Strain Gauge Module

What is the Alpha 614 Strain Gauge Module?

The 614 and 614A provide 16 three-pole channels, which can be used for voltage or current measurement at up to 19 bit resolution and 1uV integrity. Pairs of these channels can be combined to make strain gauge measurements with six poles. Full, half and quarter bridge strain measurements are supported. The measurement resolution of a 350 bridge with two active gauges can be as high as 0.1uE. Strain energisation is by constant voltage with full remote sensing to eliminate lead and connector resistance errors. The bridge supply is directly derived from the A-D reference so that the effect of drift in these circuits does not affect measurement accuracy. Initial bridge unbalance can be compensated for. High quality cage clamp two part screw terminals are used for all connections.

The 614\614A can be programmed to integrate signals to be measured over one or more complete mains cycles (50 - 60 Hz) allowing measurements to reject large levels of mains borne interference super imposed on micro-volt signals. During a measurement an auto-ranging facility ensures an input channel is measured on the best range to maintain maximum measurement resolution. A choice of measurement conversion resolution and speed is provided. These features together with a digital filter function and precision hardware design achieve excellent noise performance in strain gauge applications and general voltage measurements.

Measurements, measurement linearisation, measurement processing and communications are concurrent tasks for optimum performance. Calibration is performed by applying reference inputs and issuing commands to the module. No internal access is required. 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. Customised display output can be provided.

LOCAL OUTPUT FACILITIES ( 614A )

The 614A can be used with an auxiliary output termination panel. This connects to the 914 with a 10-way ribbon connector. A number of digital outputs and digital inputs can be provided on this panel. These can be controlled directly using commands sent on either serial interface. Alternatively the standard firmware can be configured to utilise this auxiliary I/O in a particular way for an application. Such a function can run independently of any communications from a host computer. For example they could be used to drive a local status panel, or provide synchronisation to external equipment or events.

 

Features

• Strain, Voltage and Current inputs in compact DIN rail module.

• Up to 16 Voltage or 8 Strain channels

• 13 to 19 bit resolution.

• 200 to 10 measurements per second

• Programmable Measurement Types

• Full, half and quarter strain bridge support

• 120R to 1000R Gauges

• Auxiliary I/O expansion (614A option)

• Scaling, alarm levels, filter functions

• Second local diagnostic serial interface

• High speed communications

 Specification Details

Number of channels / module: 16

Number of 6 pole channel:up to 8

Number of 3 pole channels: up to 16

Connector type input channel: 2 part screw terminal high quality cage clamp

Measurement modes: Voltage - uV DC, mV DC, 4-20mA, ¼ bridge strain, ½ bridge strain, Full bridge strain

 

 A-D Converter

5 Measurement resolutions are supported:

19 bits at 10 measurements/s

18 bits at 20 measurements/s

17 bits at 40 measurements/s

15 bits at 100 measurements/s

13 bits at 200 measurements/s

In addition a channel filter function can be applied to any channel.

 

Voltage Measurement

Input voltage ranges: +10V to-10V,  +1.5V to-1.5V,  +180mV to-180mV,  +23mV to-23mV

Automatic range selection is supported.

DC measurement accuracy: +/- 0.015% of reading + 0.01% of range + 6uV

Temperature coefficients DC voltage: 25ppm rdg + 0.1uV/ ° C

Measurement sensitivity: -23mV range at 18bits

Note: Displayed sensitivity depends on reporting format.

Additional error at 200/sec mode of 0.05% of range. 

 

Strain Measurements

Bridge Configurations:

Full>=350R

Half>=350R

Full 120R (option)

Half 120R (option)

Quarter External Dummy

Bridge Supply: Voltage remote sensed

Bridge Voltage: 1.7V to 5.0V depending on mode of resistance

Accuracy:

350R Full: 0.05%rdg+3uE

350R Half: 0.05%rdg+5uE

120R Full: 0.05%rdg+6uE

120R Half: 0.05%rdg+5uE

Measurement repeatability 24Hrs: 2uE

Sensitivity:

350R Half, Full, 120R Half

0-7000uE: 0.1uE

7000-12000uE: 0.8uE

120R full bridge

0-10000uE: 0.2uE

Temperature coefficient:

350R Full: 0.003%rdg/°C

350R Half: 0.003%rdg+2uE/°C

120R Full: 0.003%rdg/°C

120R Half: 0.003%rdg+2uE/°C

(Accuracies are stated for gauge factor 2, 2 active gauges, 18 bit ADC, at 23°C for 1 Yr) All specifications subject to change without notice; correct at time of publication. Issue 5.01 DS914A04 refers to 1.05 firmware.

Interference Rejection

AC Common mode rejection ratio channel group: <0.1uV/V

AC Single channel common mode rejection ratio: <1uV/V

DC channel common mode rejection ratio: <5uV.V

AC series mode rejection ratio 50 or 60 Hz +/- 0.05%: <1mV/V

(Applies to 17,18,19 bit measurements)

Maximum voltages operating:

Max. voltage between any (+) and (-) inputs: 12V

Max. voltage between any two (-) input terminals: 11V

 Max. voltage between any two terminals: 22V

 

Overload Protection

Channel Overload Protection:

Passive

50V continuous

150V for short periods

 

Auxiliary Channel Expansion (614A)

Connector type: 10 Way IDC

Compatible termination panels: Contact supplier

 

Power Requirement

Connector: 2-pole screw terminal

Voltage: 24V AC I,  12 to 28V

DC Current: 200mA at 12V,  120mA at 24V

 

General

RS485 INTERFACE: See Manual,  Baud rates to 153KB

Local series interface: RX TX 0 to 5V levels Compatible with most RS232 peripherals

STATUS LED’s: 2

Function: Power / Fault comms

Size: 180*100*40mm

Weight: 400g

Mounting: DIN rail,  Stackable

Operating Temperature Range: -20 to 70°C

Relative Humidity (noncondensing): <90% 0 to 40°C

Vibration:  3g 0hz to 400Hz in 3 planes

Programming storage: Secure flash memory

Stated Accuracy’s are at 23° C

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