Fun thoughts about Ludlums.

[James Luck]

So for sometime I had the thought that it would be cool to modify a Ludlum 14c to use a different internal probe. Rather this was a large tube deck or a gamma scintillator instead of its higher range GM tube.

This would of course require a deeper can. Well I received the other day my newest instrument, a beautiful model 9 ion. Seller refurbished the instrument to factor quality, and she's still within margin of calibration. off topic now my idea to set a model 14c into a deep can wont work. The size of the can tops for the larger model 9 are not the same. shame although I could've seen this one coming.

I should add yes Ludlum makes a meter that has a internal scint and external port. The model 3-97 Norm. Mor designed for lower range, versus high range scintillation counting.

Well now my idea shifts towards the Ludlum micro R meter, specifically the model 12s or 19. In a new pace modifying the meter to have a external port. With the idea of using a alpha beta sensitive external detector, and a moderate range internal for gamma.
Ofcourse I wont be taking parts from high quality meters, mostly beat up and damaged ones.

Have anyone here experimented with modifying meters to fit parameters you wish the meter had? Just thought this might be a cool topic to pick some minds.

On a side note I'm happy to say two of my meters will be off to Ludlum Measurements for work & calibration. A vary well kept 17-1 ion and a somewhat beat up 14c. Both need a good look threw, especially the 14c who's response is far from what it should be.

[Sparky]

James,
I think your taste is definitely for the fancier Models. I like the Model 2 because they can be obtained for very little money (often less than $100), but the front end is the same as the Model 3. The Model 2 has one less range setting than the Model 3, which reads up to 500,000 CPM. I have seldom needed to go over the 50,000 CPM limit of the Model 2. I have one that is about a 1983 vintage and another which I believe is a 1990. I like these older versions because the electronics is simpler and the case is roomier and they are cheap enough to modify without too much concern.

I have installed meter cards into both meters for CPM only. I have a large variety of probes and dosimetry is not really my thing, so CPM is better for me. Both are kept in tune with my homemade pulse calibrator, but they rarely need adjustment.

I modified both of them by JB Welding a small aluminum plate to the case that had been drilled and tapped to fit a clamp for my end window GM probe. The same clamp will also fit my homemade “sidecar” digital counter. Both meters tops have been drilled for a 3mm mono audio connector to provide the signal to the counter from the first trigger IC of the Ludlums. This arrangement allows me to remove the counter and go back to normal analog operation, which is how I use it 99% of the time. The digital counter provides CPM and CPS rate meter functions. In CPM mode it displays two lines, one for a 6 second average, the second for a 1 minute average, updated every 6 seconds. This is similar to the slow/fast feature of the analog meter. CPS is a single line, 3 second average. The CPS feature provides the high rate capability missing on the Model 2 and is well suited for scintillator operation. Other features are pre-set 10 minute and 20 minute scaler periods and a small data-logging capability. The backlight has been pretty handy a few times also.

I also added a 10 turn pot to the HV adjustment of the older M2. It allows very precise adjustment of the voltage and in conjunction with the Digital counter is very good for GM plateau testing or voltage characterization of scintillator probes.

The photo in the desert is at the Trinity site in New Mexico. That homemade plastic scint usually reads about 1500 CPM in my house.

[James Luck]

Yes sparky my taste is better suited for the fancier models, that Ludlum and also Eberline produces. That's probably why I own three Eberline ESP-1's, a model 9 and two 17-1 ions, and many more.

I usually dont need more than 500kcpm for my normal usage, and honestly if I needed one the Esp-1's will go up to 1 million cpm and higher.

Although on occasion I may be known to be doing super fine background measurements for the physics department of high school I graduated from. In such cases large sensitive instruments with high count rates, that most meters wont hit.
-One such example was seeing what percentage without approximation, so exact decimals was the new sand for their baseball feilds. Fun exparement to say the least.

I dont usually have a use for dosage, but that's what the ion chambers, and a Ludlum 14c with a proportional tube is for. On occasion it's kinda nice to have a rough estimate on what I may expect dose wise.
I do have a Ludlum model 2, main boards manufacturer's date says 95, And compared to my Esp-1's which still fit factory data sheets, I have a rough idea that its within range.
A pulser is in the works
The model two peaks its scale out at 50Kcpm, not a bad instrument. Probably will be leaving my hands soon to be a gift to a past teacher, who is in the market for one.

More or less it's the moding thats caught my attention as of recently. Sorta watching people make new instruments from old and true ones. Not to mention the occasional ones made from matched parts that a engineer at a lab or plant put together on his spare time.
The drive to find a meter that is as best of a kill all, than just one purpose. If time and money allows.

-james.
Ps: sorry for the long response back. Sort and sweet isnt my thing usually.

[James Luck]

Yes sparky my taste is better suited for the fancier models, that Ludlum and also Eberline produces. That's probably why I own three Eberline ESP-1's, a model 9 and two 17-1 ions, and many more.

I usually dont need more than 500kcpm for my normal usage, and honestly if I needed one the Esp-1's will go up to 1 million cpm and higher.

Although on occasion I may be known to be doing super fine background measurements for the physics department of high school I graduated from. In such cases large sensitive instruments with high count rates, that most meters wont hit.
-One such example was seeing what percentage without approximation, so exact decimals was the new sand for their baseball feilds. Fun exparement to say the least.

I dont usually have a use for dosage, but that's what the ion chambers, and a Ludlum 14c with a proportional tube is for. On occasion it's kinda nice to have a rough estimate on what I may expect dose wise.
I do have a Ludlum model 2, main boards manufacturer's date says 95, And compared to my Esp-1's which still fit factory data sheets, I have a rough idea that its within range.
A pulser is in the works
The model two peaks its scale out at 50Kcpm, not a bad instrument. Probably will be leaving my hands soon to be a gift to a past teacher, who is in the market for one.

More or less it's the moding thats caught my attention as of recently. Sorta watching people make new instruments from old and true ones. Not to mention the occasional ones made from matched parts that a engineer at a lab or plant put together on his spare time.
The drive to find a meter that is as best of a kill all, than just one purpose. If time and money allows.

-james.
Ps: sorry for the long response back. Sort and sweet isnt my thing usually.