Monitor Newsletter 179: Strain Measurement over Internet; Excel, Saving Files Every Day

-------------------------Monitor------------------------
The Newsletter for PC-Based Data Acquisition and Control
Issue 179         www.windmill.co.uk           June 2013
--------------------ISSN 1472-0221----------------------

Welcome to the June issue of Monitor: I hope you find 
it useful. We've a new strain measurement package 
detailed below, example macros in Excel to save files 
every day and a new section answering some questions 
you've asked recently on using Windmill.  

For more measurement and control discussion and tips 
see the Windmill web site and join us at Google+.

Should you wish to remove yourself from our mailing 
list please go to 
Monitor Newsletter

CONTENTS
========
* Monitor Strain Gauges over the Internet
* Excel Corner: Saving to a new File Every Day
* We Answer your Windmill Questions
* DAQ News Round-up

  
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Monitor Strain Gauges over the Internet
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A new strain data logging package is now available from 
our on-line shop at 
https://www.windmillsoft.com/daqshop/strain-data-logger.html. 
It lets you log data over Internet or Ethernet networks.


Monitor strain gauges, pressure transducers or 
voltage signals, through 16 differential input channels
Can also monitor digital inputs, count, control 
digital outputs and measure temperature, pressure, flow, 
level, etc (extra hardware may be needed)
Includes Windmill Software: no programming required
Automatic ranging lets the software match the strain 
signal as closely as possible
Integrating analogue-to-digital converter reduces 
electrical noise
Use software to select the resolution of the A-D converter 
from 12- to 18-bits: choose between high resolution and 
high speed
Automatic recalibration
Set two alarms on each strain gauge
Measurements returned in microstrain, or engineering 
units of your choice
Use for real-time data acquisition on your PC or for 
stand-alone data logging
Free technical support for life and money-back guarantee 
if not satisfied

Measuring Strain

The 851-SG package comprises an 851 data logger, a strain 
connection box and Windmill data acquisition software. Just 
connect your strain gauges to the strain box, plug the box 
into the 851 Data Logger and away you go. This method of 
connection means you can use the 851 Data Logger to monitor, 
for example, temperature at the same time as strain.

With the 851-SG package you can 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 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.

More information:
https://www.windmillsoft.com/daqshop/strain-data-logger.html
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Excel Corner: Saving Logged Data to a New File Every Day
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After last month's article on automatically saving an 
Excel file, a reader got in touch to ask how he could 
save data in a new file every day. He was using Excel 
to continually log data every 5 seconds. 

To save in a new file daily you need to add just a few 
lines of code to your logging macro. We give details 
below, and an example at 
https://www.windmill.co.uk/excel/data-logging.xls

1. Add: 
   Application.OnTime TimeValue("00:00:00"), "SaveNow"
   Where: 
   TimeValue specifies the time of day to save the file. 
   In our example at midnight.
   SaveNow is the name of a subroutine containing the 
   instructions to save the file.

2. Create a new subroutine to save a copy of the current 
   worksheet in a new file. We do it this way, rather than 
   saving a copy of the current workbook (which would take 
   less code), as we don't want to also save the data 
   logging macros with each file. The subroutine should:
   a. Check whether the new filename exists (so as not 
   to overwrite any existing file)
   b. Copy the worksheet and save it as a new file.
   c. Close the new file.

For example

  Private Sub SaveNow()
  Dim Fname As String
   Fname = "Data" & Format(Now(), "yyyymmdd") & ".xls"
   If Dir(Fname) = "" Then
    ScreenUpdating = False
    Dim wb As Workbook
    Worksheets("Sheet1").Copy
    Set wb = ActiveWorkbook
    wb.SaveAs Fname
    wb.Close
    ScreenUpdating = True
  End Sub

Notes:
ScreenUpdating = False stops Excel redrawing the screen 
which may speed up the Save operation
The file will be saved in the format Data20130620.xls, 
where 20130620 represents today's date
ScreenUpdating = True re-enables the screen updates.



The code saves a series of files every day. However, 
it doesn't delete the data once saved. So each file 
will contain all the previous days' data as well as its own.

To save just that day's data, you will need to delete 
the contents of the main file after each save. Add this 
code to your SaveNow subroutine after changing 
data-logging.xls to your worksheet name, and Range("a2") 
to reference the cell holding the first data value:
Workbooks("data-logging.xls").Sheets("Sheet1").Range("a2").Select
    Range(Selection, ActiveCell.SpecialCells(xlLastCell)).Select
    Selection.ClearContents
		
It will select and delete everything below the first row, 
so each file will contain just that day's data.

If you are nervous about automatically deleting data, you 
can use Windmill Logger to save data at the same time as 
Excel. That way you can be confident that you have a 
back-up that can later be imported into Excel if necessary.

More Excel data logging macros are on our website at 
https://www.windmill.co.uk/excel/excel-tips.html

Have an Excel question or tip? Want more details on 
logging with Excel? Contact monitor@windmillsoft.com.
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Questions on Using Windmill
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Welcome to our new, occasional, slot answering questions 
we've been asked this month about using Windmill. If you 
have a question e-mail techsupport@windmill.co.uk.

Question:
  We have an request for data logging via Modbus TCP/IP 
  and we are evaluating your software Windmill 7 Data 
  Acquisition Software. The customer wants us to generate 
  a text file on a PC. This should work with your product, 
  right? The additional requirement is that the software 
  has to generate a new file every day. Is the software 
  able to do that as well?

Answer:
  The short answers are yes and yes. Windmill Logger saves 
  data in text format, and can save to a new file every day. 
  Subscribers can download a trial of Logger, and the rest 
  of Windmill. 
  The trial contains a software signal generator, which you 
  can use to experiment with the Windmill programs without 
  worrying about any hardware settings.

Question:
  I have been working with ComDebug and gotten for the 
  most part the results that I have wanted. I was able to 
  parse the data correctly received from the scale, but I 
  am not sure how to get an actual 'Real-Time' display from 
  the scale.

  I don't know if its on the scale end or settings on the 
  computer/software end to get the scale to read exatly 
  what it says when told to. Right now it waits for the 
  reading to balance out, and I miss quite a bit of readings.

  I will keep doing some research, but any additional 
  help would be greatly appreciated! 

Answer:
  On most scales you can choose either to wait until a 
  reading is stable, or to take a reading right away. 
  How you do this depends on the scale. For example, 
  with a Mettler scale you would use an S command to 
  request a stable reading and SI to tell the scale 
  to send the reading immediately. Other scales, like 
  those from Sartorius, let you choose from four options 
  covering Very Stable to Very Unstable. So change the 
  settings on the scale to prevent missed readings. More 
  details for how to do this on different balances are at 
  https://www.windmill.co.uk/serial_driver.html
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DAQ News Round-up
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Welcome to our round-up of the data acquisition and 
control news.  If you would like to receive more 
timely DAQ news updates then grab our RSS newsfeed 
at https://www.windmillsoft.com/monitor.xml.  Read 
https://www.windmill.co.uk/newsfeed.php for notes
on how to display the news on your own web site or 
automatically tweet it.

Better design tests needed for medical devices
   The medical technology sector needs better ways of 
   demonstrating the safety, effectiveness and 
   performance of its products, says a new report.
   Source: MIT Technology Review
   https://www.theengineer.co.uk/
	
Snow sensing helps predict water shortages 
   Precisely measuring supplies of meltwater could help 
   farmers in the US plan what they plant in order to 
   battle a changing climate.
   Source: New Scientist
   http://www.newscientist.com/
	 
Materials Scientists Build Chlorophyll-Based Phototransistor
   Coat a layer of graphene with chlorophyll and you 
   get a remarkably sensitive light-activated switch, 
   say researchers at the Institute of Atomic and 
   Molecular Sciences in Taiwan.
   Source: MIT Technology Review
   http://www.technologyreview.com/

Intrinsic Safety Drives Process I/O Module Market
   According to a study by ARC Advisory Group, the global 
   process automation I/O module market grew in 2012, but 
   not by as much as in the previous two years. They 
   predict that the process I/O module market will resume 
   growth at an above average rate during the next 
   five years.
   Source: ARC Advisory Group
   http://www.arcweb.com/
	 
NIST Researchers Offer Tool to Aid Standards Implementation
   The nice thing about standards, it's been said, is 
   that there are so many to choose from. Now comes a 
   serious effort by National Institute of Standards 
   and Technology (NIST) researchers to develop a 
   computer-aided method for analyzing, comparing and 
   testing standards, from the conceptual stage all 
   the way through to implementation and beyond to rounds 
   of updating and revising.
   Source: NIST
   https://www.nist.gov/
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* Copyright Windmill Software Ltd
* Reprinting permitted with this notice included
* For more articles see https://www.windmill.co.uk

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Windmill Software Ltd, PO Box 58, North District Office,
Manchester, M8 8QR, UK
Telephone: +44 (0)161 834 6688
Facsimile: +44 (0)161 833 2190
E-mail: monitor@windmillsoft.com

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