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BUG: Running OFDA on fast Pentium computers
Coefficient of Variation (CV) of diameter
Video Frame Grabber card upgrade
DIAM: Latest version and list of recent changes
Slide Scratches
New Spreader

BUG: Running OFDA on fast Pentium computers

We have found a bug in the diam.exe program that causes intermittent "bad light" errors during measurement. It occurs only on computers that are Pentium 133 or faster. On very fast computers such as PentiumII-233, diam may not measure at all ("can't set light" error at beginning of measurement).

The bug has been fixed and all diam.exe versions dated after 29 April 1998 are OK. The bug did not cause measurement errors, and there is no need to recalibrate when updating to this version from any diam version 2.00 or later.

Coefficient of Variation (CV) of diameter: the effect of excessive maximum diameter

OFDA can measure diameter up to 300µm. This can cause problems for measuring certain fleece samples that contain fibrous vegetable matter. We have seen an example of a fine fleece sample that contained a single piece of fibre-like VM at 130µm and the effect on the CV of diameter is much greater than one might imagine.

For example: 4000 fibre snippets are measured from a fleece sample

Sample Mean Diameter SD Diameter CV Diameter
Clean 16.81µm 3.53µm 21.0 %
With one 150µm fibre added 16.84µm 4.11µm

24.4 %

The solution is to set the max diam in the calibration menu for the calibration used to as low as possible for the type of fibres you are measuring. For typical fleece measurement in the 18-30µm mean diameter, a max diam of 80µm is recommended. Fibres wider than this diameter will then be ignored.

Video Frame Grabber card upgrade

The card that plugs into the PC and captures the images is known as the Vdig card. Earlier OFDAs were shipped with the Vdig1 card, but in 1993 a new card known as Vdig2 was developed and all OFDAs after early 1993 were equipped with this card. The two cards are compatible; the advantage of the Vdig2 card is that it will run the medullation measurement (with extra components required) and will run the normal diameter measurements about 50% faster.

To detect which Vdig card you have:

  • If you are running software version 1.xx, then you will be using Vdig1.
  • If you are running software version 2.xx, then select Vdig status under the Technical menu. It will display a line saying Vdig1 detected or Vdig2 detected.

The benefits of the Vdig2 card are only obtained after upgrading to version 2 of the software. Vdig2 is simple to install: just remove the Vdig1 from the PC, plug in the Vdig2, install the software 2.xx (if not already installed) and the software will automatically detect the version of the Vdig card.

DIAM: Latest version

The latest version of Diam (OFDA operating software) is 2.09
If you would like to upgrade your version of DIAM, please contact us or go to our download page.

Recent changes to OFDA software
17 July 97 Release 2.08, changes from 2.05


Diameter Whole slide scanning
If doing whole slide measurement, OFDA will continue doing whole slide scans until the sample limit is reached (to comply with OFDA IWTO Test Method 47).
Medullation In medullation measurement, pressing F3 key will toggle display of opaque fibres in 50um diameter groups.
Curve Removed need for licence file to enable curve or blob factor. All diam programs have these options included. Licence number in licence file still required for medullation measurement.

Blob factor and along fibre

Added capablility to measure blob factor and along fibre segment diameter.
Mes file Blob factor and along diameter added to mes file, and also exported in .sp2 spreadsheet format from Meswork. Calibration data has been added to each mes file record to allow retrieval of the calibration used for each measurement.
File Menu /
Mes file directory
Option has been added to allow selection of a different directory to store mes files in, rather than just saving them in the current directory.

1 Oct 95 Release 2.05, changes from 2.03


Help Added online help. Help has the same or more recent content as chapter 4 (Software Reference) of the OFDA Reference Manual. Press F1 key for help at any time.
Measure menu selection Now pops up a window showing current file name, client, operator,sample ID and description. Allows operator to check and alter these before measuring. A warning flashes at the screen bottom if the operator has not selected a mes file to save data.
Curve Increased curve measurement accuracy for fibres with curve near 0. Increased maximum size of curve histogram from 360 deg/mm to 500 deg/mm.

Altered definition of flat fibre. See online help. Increased maximum light width from 99 to 200um, and reduced resolution of light width histogram from 1um to 2um steps. Added print of dark flash length to calibration line in print header.

Install new light option Added Setup/Install/LED option to assist in installing or adjusting the LED (light emitting diode) that is the OFDA light source.
Mes file If medullation option is installed, mes file header now has opacity calibration data when a new mes file is created.



Protected mode MesWork.exe is now a protected mode program which means it can access the computer's full memory, allowing files of up to 5000 measurements to be handled. It will only run on a 286 or higher PC. If called from within DIAM, it must have the files RTM.EXE and DPMI16BI.OVL in the current directory or path. RUNDIAM must be typed to provide access to the extra RAM that will allow MesWork to be called from within DIAM (File/Read mes file option).
Sorting Sorting order has been improved to better handle identical sample ID and description fields.
Curve and opacity Curve and opacity measurements can now be read back from mes files if those options were specified at time of measurement.
Output formats Spreadsheet format .sp2 has been greatly extended to contain all measurement data.

Slide Scratches NOT a Problem

There is some recent concern that the OFDA is measuring scratches. This is a very minor problem: it is possible for the OFDA to measure a scratch if it appears to be like a fibre, but the chances of hitting on the part of the slide with a scratch in-focus are small:

• the scratch must be on the inside surfaces of the slide. Scratches on the outside of the slide are too far from the point of focus to even be seen by the OFDA.

• scratches are optically different to fibres.

• one experiment involved scratching a slide over the FULL width 50 times with a screwdriver and obtained only one measurement on wholeslide*2.

• scratches must be appear in the video image to be like a fibre. For instance, the scratch must be less than the cutoff value (usually 150 microns) in diameter, must have parallel sides and must appear completely black like the fibres in the image.

• we have known for several years that severe scratches can be measured, but only 1 laboratory out of 100 has reported the problem due to a metal vacuum cleaner nozzle. It took years of using the same slides for thousands of measurements before the scratches appeared in some results.

• a test house in New Zealand measured all their 5 year old slides after thousands of measurements and found an average of less than 2 measurable scratches per slide. This is insignificant for a measurement result from 2000 fibres or more.

• the IWTO OFDA Test Method, TM-47-95 is to be amended to include a statement about not using slides with scratches.

Anyway, the best way to avoid this problem is to ensure that you don't use slides with scratches on them! Therefore:

• Keep your slides clean and free from scratches. Do not use metal cleaning nozzles on the slide. Be vigilant if you are measuring samples with a lot of sand or grit; note however that sand scratches are unlikely to be measured because they are short and and lack the "fibre-like" characteristics.

• Test your slides for scratches. This is simple: just measure your empty slides.

1. Adjust your focus on a slide with some fibres in it

2. Brush the inside of the slide clean

3. Measure the slide on "whole slide * 2"

4. If you get more than, eg. 4 or 5 measurements then discard the slide

5.Repeat steps 2 to 4 for all your slides.

• Check your slides regularly (every couple of months).

• Contact us to purchase replacement slides.

• Just use a brush or cleaning device with a plastic nozzle to remove fibres.

New Spreader

The Spreader Mk2 is now available. The advantages over the old spreader are:


Faster, more uniform spread


Less fibres thrown out


More compact: control box is fixed to spreader


Simpler to use: push green button to start, push red button to stop.


More reliable: steel geared motor with microprocessor control.

It is recommended that all customers upgrade to the new spreader. For maximum accuracy, the OFDA must be calibrated with the same spreader type that day-to-day measurements are made (ie. the old and new spreader can not be used together)

Design by Arno Münzer