Graticule (reticle) for Velleman HPS140 Digital Oscilloscope
by nwlaurie in Circuits > Tools
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Graticule (reticle) for Velleman HPS140 Digital Oscilloscope
The Velleman HPS140 digital oscilloscope at around £100 ($150) is a great little instrument but suffers from only having edge-scales rather than a full graticule. Since the device is good enough for rough 'n ready measurements of fairly high standard, and given that my old eyes can struggle a bit with tiny things I turned to the interweb for an answer.
Found just one on the Velleman site where a chap said he'd drawn marker-pen lines on a slice of screensaver. I wanted just a little bit better than this and in spite of endless searching came to the conclusion that I was going to have to do it myself.
More searching found nothing very useful in the way of grid-drawing software so I turned to Microsoft Publisher (running in Parallels on a Mac - don't worry if that means nothing to you) and half by calculation and half by empirical 'bit-bigger-that-way' twiddling ended up with the attached file.
I printed half a dozen copies on a single sheet of acetate because the acetate was patchy and I also knew it would take several attempts to cut it to fit. It did!
I'm NOT a perfectionist and good enough was near enough for me - you may want to do better...
The sums:
Vertical 0.7mm for each of 24 on-screen dots = 16.9mm@ 3 divs per 'dash'
Horizontal 0.7mm for each of 58 on-screen dots = 40.9mm @ 5 divs per dash
Offset from origin is arbitrary and done by eye with scissors later.
Found just one on the Velleman site where a chap said he'd drawn marker-pen lines on a slice of screensaver. I wanted just a little bit better than this and in spite of endless searching came to the conclusion that I was going to have to do it myself.
More searching found nothing very useful in the way of grid-drawing software so I turned to Microsoft Publisher (running in Parallels on a Mac - don't worry if that means nothing to you) and half by calculation and half by empirical 'bit-bigger-that-way' twiddling ended up with the attached file.
I printed half a dozen copies on a single sheet of acetate because the acetate was patchy and I also knew it would take several attempts to cut it to fit. It did!
I'm NOT a perfectionist and good enough was near enough for me - you may want to do better...
The sums:
Vertical 0.7mm for each of 24 on-screen dots = 16.9mm@ 3 divs per 'dash'
Horizontal 0.7mm for each of 58 on-screen dots = 40.9mm @ 5 divs per dash
Offset from origin is arbitrary and done by eye with scissors later.
Laser printed - the actetate curled badly (old, damp?) but fortunately I'd done many copies per sheet; then roughly cut out.
I tried using the ink-jet with a pale blue grid but it smudged too easily.
Make sure you put the printed side facing inwards.
With the final version I left the bottom-most line un-printed since the alignment discrepancy didn't show so much that way.
(like I said: 'near enough is...')
I tried using the ink-jet with a pale blue grid but it smudged too easily.
Make sure you put the printed side facing inwards.
With the final version I left the bottom-most line un-printed since the alignment discrepancy didn't show so much that way.
(like I said: 'near enough is...')
Now to cutting. I settled on four attempts before reminding myself that 'good e...' - you know the rest!
Used a scalpel tip to roughly mark the corners then trimmed down bit by bit until it (near enough) fitted.
Voila!
Used a scalpel tip to roughly mark the corners then trimmed down bit by bit until it (near enough) fitted.
Voila!
Final step is making it stay in place. At the moment it's a push-fit and seems to hold fairly well; I don't want to spray glue it because the device's front screen seems pretty flimsy (and prone to scratches) as it is.
The loose fit lets me jiggle it around when I need better alignment but is only half an answer (and a whole excuse).
So it's over to the massed ranks of Instructable geniuses (genii?) to come up with an idea for final fixing.
Over to you!
(oh, and as soon as I can work out where to put the Publisher file, you can have a copy! Meanwhile email me at nwlaurie@me.com if you want a copy)
The loose fit lets me jiggle it around when I need better alignment but is only half an answer (and a whole excuse).
So it's over to the massed ranks of Instructable geniuses (genii?) to come up with an idea for final fixing.
Over to you!
(oh, and as soon as I can work out where to put the Publisher file, you can have a copy! Meanwhile email me at nwlaurie@me.com if you want a copy)