Calibrating a NuArc integrator... Sandy King?
I've read on one of the forums somewhere.. maybe here, a post from
Sandy King describing how he calibrated his NuArc exposure unit so
that one "unit" equaled 1 second. I've been trying to do the same,
but am having a hard time getting it to work. My unit has an "eye"
mounted on top of the brackets that hold the lamp in place. The
eye is in a cylindrical black housing that can be tilted at different
angles. It also has a disk mounted over the eye... this disk can be
rotated, and as it's rotated, the eye is totally exposed, then gradually
the eye is blocked more and more by black paint on the back of the
disk. I assume this is for adjusting the sensitivity of the eye, and
therefore, the value of one exposure unit.
I hope Sandy sees this thread because it's all his fault I've opened
up this particular can of worms! :o)
Can anyone shed some light (har har) on this little gadget and how
to adjust it? Sandy just talked about aiming the eye more or less
toward the lamp, but with my unit, the eye seems aimed at the
metal brackets above the lamp, and I can't see where it can... "see"
the lamp at all, no matter how it's adjusted.
Susan, I wonder why it is so important to have it match seconds. I ususally print by units just fine. I am a little puzzled there.
I have not done that but I suppose you could adjust the distance of the UV sensor so that it will count faster or slower according to your needs.
Originally Posted by suvo
I have a 26-1K and have been in the dark all day and just noticed your post taking a break. The integrator has a dial that you can turn. If I recall correctly I set mine on the lower number,possibly 2 or 3. I tried to set the dial then turned it on to time it to seconds but it is really not that necessary to have them equal. Just time the units with a watch and write on the front what 100 units is and 200 is etc..You never will have the units stay at the same seconds anyway due to the degredation of the lamp over time. My units are 100=2 min, 200=5min and 300=8 min. Don't worry about having 1000 units=1000 minutes. It ain't gonna happin. Leave the integrator pointing where it was when you took the top off. Hope this helps.
I meant to say that 1000 units will not have to equal 1000 seconds. Sorry for the confusion.
Originally Posted by Brickbird
Hi all, and thanks for the responses!
You're right of course, that it isn't absolutely necessary to have each unit = 1 second, but it just seemed to make sense to me to start off with mine that way. I just got it, and am still finding my exposure times for polymer gravure plates. Sandy's original post made it sound like such an easy adjustment, that I thought I'd do it with mine too.
Another thing... my exposures (there have to be 2 exposures per plate), are going to be in the 30 to 40 second range. What I've found is that the bulb takes that long to come up to full brilliance. That wouldn't be a problem for long exposure times, because the integrator does it's job... but what happens with a shorter exposure time? That's one reason I'm interested in having my "units" well calibrated.
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Susan....My suggestion would be to find some rubylith material or just use a large piece of mounting board to cover up your polymer and wait for the light to come up to full lumens and then remove it. Start your unit timing from that point. If you are only doing that process for a while then you might want to turn your integrator wheel to a different number to slow the "unit per second" timing. Any printing company that had a NuArc might still have some ruby material laying around. It is a dark red masking material used to block UV light while making plates "in the old days". I sent you a pm with my numbers if you would like to call.
Originally Posted by suvo
Hi Tav, and thanks for the help! I got swamped today after I wrote the posts above, and didn't have time to get back to it. Tonight is busy, too... I"ll be back here tomorrow and and we'll get this thing figured out! Thank you very much for the help... see ya
Of course you can make one unit on the NuArc equal whatever length of time you like, but I personally like to calibrate so that one second of time equals one unit of exposure. If nothing else establishing the rough equivalence makes it easier to exchange exposure data with other people.
How to do it? First, unplug the NuArc and then remove all of the screws on the top. Then, carefully lift the top and move it back out of the way. Be careful when doing this to avoid damage to the power cord of the fan.
You can adjust exposure by two different mechanisms. At the very front of the unit, in the middle, is the light sensor. You can adjust it by moving it up and down so that it sees more or less of the hole that looks down to the bulb, or you can adjust it by opening or closing the filter on the front of the sensor. If you want to adjust to one second of time equal one unit of exposure, first turn on the unit and allow the bulb to warm up for about a minute. Then open (or close) the filter (or adjust the sensor away from or toward the opening to the bulb) until time and units match. There is no point in perfect eqjuivalence so don't obsess too much about perfection in carring out this operation.
Which model nuArc are you working with?
Originally Posted by suvo
I designed the SM2100 and EZ-1 integrators for nuArc and am familiar with some of their lower-end integrators.
It is customary to initially have the integrator work at 1unit = 1second. The integrator and sensor are designed for optimum performance at this calibration. If the unit is counting too fast the pre-amplifier may be saturating - too much light is getting to the photocell and the integrator can't handle the signal.
If you set the unit to 1:1 with a new lamp it is easier to monitor the fall off in light output as the lamp ages. When it slows to 1/2 speed it is a good idea to replace the lamp.
OK life slowed down enough for me to get back here...
Hi Sandy, and thanks for the information. The past few days
I've become pretty familiar with the inside of the Nuarc as I've
tried to get it adjusted as you'd suggested.
Nicholas, thanks for checking in on this. I have the 26-1K.
I'm happy to hear that you are so familiar with these integrators.
I just got it last week, and have had trouble with the light
flickering, then going out occasionally. The bulb looked old
and was quite blackened so I got a new one and installed it
last night. Then while trying to adjust the sensor early this
morning, the new light stopped working. ugh. I checked the
fuses, and one was blown. Tomorrow I have to try to find
new fuses for it ( I plan to just replace them both). Now I'm
wondering why the fuse blew, and if this thing really has some
serious problem. It's on it's own dedicated circuit that's getting
112 volts (I checked that at the receptacle), and the input
and output leads on the transformer are set correctly for that
voltage. I have learned way more about electricity and the inner
workings of this thing than I really want to know :o) I just want
to expose my plates and make some nice images.
So... Sunday I will try to get fuses and hope that fixes the bulb
situation, then maybe I can get back to calibrating it, and I
welcome help with that. Maybe the reason I had trouble getting
a repeatable result before was the old bulb.
Thanks... please stay tuned while I try to work through this the
next few days. I appreciate the help!