Friday 2 August 2013

Monitor strain gauges over the internet!

Windmill Software have launched the Microlink 851-SG Strain Data Logger, which logs data from strain gauges over internet or Ethernet. It can be used as a stand-alone data logger, or for real-time data acquisition on a PC.

As well as strain, the data logger can monitor pressure transducers, voltage signals and digital inputs, count; control digital outputs and count up to 1 million events. With extra hardware it can also measure temperature, flow, level, and other signals.

Windmill software makes the package very easy-to-use: no programming is required. Automatic ranging lets the software match the strain signal as closely as possible. Users can also select the resolution of the A-D converter from 12- to 18-bits: choose between high resolution and high speed.

Two alarms can be set on each signal input, again through the Windmill software.

Strain measurements are returned in microstrain, or in the engineering units of your choice.

They offer free technical support for life and money-back guarantee if not satisfied.

The 851-SG package can monitor strain gauge bridges and balanced bridges such as pressure transducers. It enables configuring individual channels to accept any of these inputs:
    - voltage - quarter bridge: single strain gauge
    - half bridge: tensile + compressive strain gauge
    - half bridge: normal + transverse strain gauge
    - full bridge: 2 tensile + 2 compressive gauges
    - full bridge: 2 normal + 2 transverse gauges
    - full bridge: tensile normal + compressive normal + tensile transverse + compressive transverse gauge

Strain gauges need an external excitation voltage to supply sufficient current to keep all the bridge circuits energised. The 851-SG package provides four sets of 16 screw terminals giving + and - excitation and signals for each of 16 bridges. Two 1 kOhm termination resistors are mounted in half bridge configuration whilst high quality 350 and 120 Ohm resistors can be provided for the completion of quarter bridges.

When a bridge input is selected the Windmill software monitors excitation voltage and performs the bridge calculation to produce a reading in microstrain. This eliminates errors due to changes in excitation voltage.

The initial unstrained bridge measurement is often much larger than the change in signal due to strain. If this initial value is not accounted for, it restricts the resolution you can obtain - i.e. the smallest signal you can measure. Windmill software can zero or balance the bridge, nulling the offset of the initial voltage. So instead of measuring over a wide range, 0 to 0.5 V for example, you can choose a narrow range such as 0 to 0.01 V.

Each range is divided into a fixed number of steps: the resolution. The smaller the range and the larger the resolution, the more precise the reading. The 751-SG offers a choice of resolutions from 12-bit for fast sampling to 18-bit for greater precision.

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