Windmill 751-SG - Strain Monitoring and ControlThe 751-SG package comprises Windmill 6 Software for Windows, a USB unit providing differential inputs to monitor 16 strain gauges or voltage signals and a strain gauge connection card. Connect 8 USB units to 1 PC to monitor up to 128 strain gauges. The units also provide digital input and output and counting. When a bridge input is selected the Windmill 6 Software automatically monitors excitation voltage and performs the bridge calculation to produce a reading in microstrain. This eliminates errors due to changes in excitation voltage. You can also set a zero reference level and monitor changes relative to that level.
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Features
- Monitor strain gauges, or voltage signals, through 16 differential input channels
- Switch up to 32 digital outputs
- Monitor up to 32 digital inputs
- Count events with up to 8 counters
- Options to also monitor temperature, pressure and current
- Includes the powerful yet easy-to-use Windmill 6 Software for Windows: no programming required
- Portable, laptop, desktop and networked data acquisition
- Powered from the PC
- Low power consumption
- Connect up to 8 USB units to one PC, giving 128 strain or voltage inputs and 256 digital inputs and outputs
- Choice of four analogue input ranges, selected with Windmill software individually for each channel
- Alternatively, choose automatic ranging and let the software match the input signal as closely as possible
- Integrating analogue-to-digital converter reduces electrical noise
- Use Windmill to select the resolution of the A-D converter (from 12- to 18-bits): choose high throughput or high resolution
- Automatic recalibration
- Comprehensive User Manual
- Free technical support for life
What is the USB?
USB, or universal serial bus, ports are found on most new computers. They are gradually replacing the serial and parallel interfaces we're used to. As well as using the USB port for strain measurement, you can connect peripherals like printers, scanners, digital cameras and telephones. You can unplug USB devices then plug them back as you wish, with no need to restart Windows inbetween.
Strain Measurement
The Windmill 751-SG package lets you monitor strain gauge bridges and balanced bridges such as pressure transducers. You can configure 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 751-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. The auxiliary channel of the 751 USB unit is used to monitor the excitation voltage. The analogue-to-digital converter on the 751 can directly measure voltage imbalance.
When a bridge input is selected the Windmill software automatically monitors excitation voltage and performs the bridge calculation to produce a reading in microstrain. This eliminates errors due to changes in excitation voltage. You can also set a zero reference level (point 5 above) and monitor changes relative to that level.
For more information on computerised strain measurement see our corporate site.
Digital Inputs and Outputs
The 751-SG provides 32 digital I/O lines, arranged in four groups of 8. Use Windmill to choose whether each group is an input or an output. You can read or set the state of each line individually. Alternatively, you can switch several channels at the same time.
Counters
The USB unit has eight 16-bit totalling counters. Each counter starts at zero and counts pulses to a maximum of 65535. You can reset a counter at any time from Windmill software. You can use the counters in two modes: accumulating count and resetting count. In accumulating count the counter keeps counting until you reset it. In resetting count the counter shows the number of pulses since the last reading.
You can set a scale and offset factor to the count from software. For example if the pulses came from a flow meter which produced one pulse for every 50 millilitres, a scale factor of 0.05 would give a reading in litres.
The counters are found on 8 of the digital input and output lines. You can use any of these you don't need for counting as normal digital inputs: the counts are always maintained even if you don't plan to use them.
Software
Windmill 6 Software is included in the 751-SG package! This modular suite offers data logging, charting, alarm indication, output control and DDE links to other applications like Excel. You can also add process mimic generators, sequence control and many other modules. Should you wish to program the hardware yourself, you can use the IML Tools to do so.
USB Unit Specifications
Dimensions (mm) 180 x 120 x 40
Maximum length of cable 5 m
Maximum distance from PC can be increased by
use of USB hubs
ANALOGUE INPUTS
Maximum safe input voltage:
Power supply on ±48 V
Power supply off ±33 V
Transient ±300 V
Amplifier:
Ranges (V) ±0.01, ±0.1, ±1, ±10
Common mode range ±13 V
Relative accuracy of ranges:
gain = 1000 ±0.1%
gain = 1, 10, 100 ±0.05%
Analogue to Digital Converter:
Maximum linearity error ±0.02%
Resolution Integration Time Samples/Second
12 bits 2.5 msec 80
13 bits 5 msec 64
14 bits 10 msec 48
15 bits 20 msec 32
16 bits 40 msec 16
18 bits 160 msec 6
DIGITAL INPUTS/OUTPUTS
Maximum # inputs 32
Maximum # outputs 32
(selected through Windmill in ports of 8 lines)
Power-up state all inputs
Compatibility TTL and 5 V CMOS, can be made
contact closure compatible
Range 0 to 5 V
Output capability 15 LSTLL loads
Maximum I/O speed 160 channels per second
COUNTERS
Resolution 16 bits
Compatibility TTL, 5 V CMOS, can be made
contact closure compatible
Input voltage range 0 to 5 V
Maximum count speed 160 counts per second
Ordering
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