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Author Topic: Sodium Iodide probe reading greatly affected by ambient temperature?  (Read 9170 times)

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Offline kernkraft

I went to do my inst. checks today and my probe is reading way less than its historical readings. It is kept on a loading dock and today when I came in the loading ramp door was open causing the dock to be about 45F. The last time the check was done it was a lot warmer, but I didn't do those checks so I'm unsure of the reliability of the last person's reading. Battery check sat, and I verified it is the same instrument as checked before.

So is it probable that it's the temperature change or  a bad instrument/bad operator/bad ethics?

Offline GLW

I went to do my inst. checks today and my probe is reading way less than its historical readings. It is kept on a loading dock and today when I came in the loading ramp door was open causing the dock to be about 45F. The last time the check was done it was a lot warmer, but I didn't do those checks so I'm unsure of the reliability of the last person's reading. Battery check sat, and I verified it is the same instrument as checked before.

So is it probable that it's the temperature change or  a bad instrument/bad operator/bad ethics?

Temperature,....

been there, dun that,... the doormat to hell does not read "welcome", the doormat to hell reads "it's just business"

Offline Rennhack

Cracked crystal?

Offline Marlin

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   Check the Tech Manual, many have energy dependence, temprature curves, and troubleshooting table. Not all, but a good place to start. I assume you have OOS procedure so you can tag it out and hand it over to insturmentation, unless you work for a small company with limited resources.

Offline gerald.rood

Hello,
Qualitatively I have found that exposing the detector to a constant temperature for a period of time (e.g., 12 hours) prior to counting the series of measurements to define acceptable response tolerances following calibration, can be beneficial if performed at a temperature that "simulates" the actual temperature expected during field measurement.  This is because the response of this detector is somewhat temperature-dependent - to some "degree". (LOL)
For example in a rugged environment, I place the electronics box (instrument) in an enclosure that does not fall below 40 degrees F (to prevent battery issues), and leave the cables and the detector "out in the cold" from start to finish (initial acceptance and daily source checks) for the duration of the calibration cycle.
If your environmental conditions change (change of temperature/seasons), you may need to consider revising your range to tolerance - but please, NOT without due consideration of defensible results.
Regards, Gerry

Offline GLW

Cracked crystal?

Maybe, if the unit was unsecured and somebody fumbled it to the ground or smacked it without knowing or without informing anybody,...

If the temperature change was a gradual change which coincides with the environmental cycle the crystal should not crack (sudden, extreme temperature changes are the likely culprit for that),...

If the unit was happy camper warm and then the door was opened at say 4AM that might do it, or shock the PMT, or both,...

A little neoprene insulation and a 500 ml lab bottle with the top cutaway is a crude but effective mitigator of these vagaries,...

Soda can coozies and cutaway water bottles are better than nothing for that matter,...

There is a recovery protocol for adjusting the meter response but I get paid for that level of insight, anybody who wants to give it away for free is welcome to,...

 8)

been there, dun that,... the doormat to hell does not read "welcome", the doormat to hell reads "it's just business"

Offline retread

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Maybe, if the unit was unsecured and somebody fumbled it to the ground or smacked it without knowing or without informing anybody,...

If the temperature change was a gradual change which coincides with the environmental cycle the crystal should not crack (sudden, extreme temperature changes are the likely culprit for that),...

If the unit was happy camper warm and then the door was opened at say 4AM that might do it, or shock the PMT, or both,...

A little neoprene insulation and a 500 ml lab bottle with the top cutaway is a crude but effective mitigator of these vagaries,...

Soda can coozies and cutaway water bottles are better than nothing for that matter,...

There is a recovery protocol for adjusting the meter response but I get paid for that level of insight, anybody who wants to give it away for free is welcome to,...

 8)
And not paid nearly enough, I may add! :-X
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Offline SloGlo

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I went to do my inst. checks today and my probe is reading way less than its historical readings. It is kept on a loading dock and today when I came in the loading ramp door was open causing the dock to be about 45F. The last time the check was done it was a lot warmer, but I didn't do those checks so I'm unsure of the reliability of the last person's reading. Battery check sat, and I verified it is the same instrument as checked before.

So is it probable that it's the temperature change or  a bad instrument/bad operator/bad ethics?

is this probe/instrument maintained in a fixed position on the loading dock, or is the probe fixed there and the instrument inside, or is it a totally portable combo which is simply kept on the dock? 
warm temps to 45 degrees isn't a fluctuation that would give unsat readings.  was your reading out of spec or simply less than historical and how much difference are you discussing?
quando omni flunkus moritati

dubble eye, dubble yew, dubble aye!

dew the best ya kin, wit watt ya have, ware yinze are!

Offline Rennhack

is this probe/instrument maintained in a fixed position on the loading dock, or is the probe fixed there and the instrument inside, or is it a totally portable combo which is simply kept on the dock? 
warm temps to 45 degrees isn't a fluctuation that would give unsat readings.  was your reading out of spec or simply less than historical and how much difference are you discussing?

I can't understand a word you say without your accent.

Offline GLW

is this probe/instrument maintained in a fixed position on the loading dock, or is the probe fixed there and the instrument inside, or is it a totally portable combo which is simply kept on the dock? 
warm temps to 45 degrees isn't a fluctuation that would give unsat readings.  was your reading out of spec or simply less than historical and how much difference are you discussing?

I can't understand a word you say without your accent.

seen this before,...


been there, dun that,... the doormat to hell does not read "welcome", the doormat to hell reads "it's just business"

Offline SloGlo

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I can't understand a word you say without your accent.
aye no.  eye whanted two tale alla dem teechers dat itt woodent work wail, butt yew noe watt teachars arr like.  sum sayed i hadda git rid off my ax sent, udders thaught their was know problem.  udders had scene my kind bee four.  sew, eye rolled da dice.  ;)
quando omni flunkus moritati

dubble eye, dubble yew, dubble aye!

dew the best ya kin, wit watt ya have, ware yinze are!

Offline kernkraft

Hey guys, OP here, sorry for not checking back, busy week.

I'm a dumbass, I was using the wrong side of the plastic Cs-137 source. Normally is 10k cpm, reading the wrong side made it 2000 cpm. I've only been in this job for 8 months, and just changed site locations. At the old location the guy was doing the checks from the wrong side too, so when I first started working there I used the side that agreed with the historical data. I've corrected my check and noted why it was changed. Also I have made sure everyone I work with is on the same page.

Thanks!

Offline GLW

Hey guys, OP here, sorry for not checking back, busy week.

I'm a dumbass, I was using the wrong side of the plastic Cs-137 source. Normally is 10k cpm, reading the wrong side made it 2000 cpm. I've only been in this job for 8 months, and just changed site locations. At the old location the guy was doing the checks from the wrong side too, so when I first started working there I used the side that agreed with the historical data. I've corrected my check and noted why it was changed. Also I have made sure everyone I work with is on the same page.

Thanks!

Your welcome!!! and thanks for making me chortle my lunch all over my monitor,...  ROFL ROFL ROFL ROFL

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Offline retired nuke

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Hey guys, OP here, sorry for not checking back, busy week.

I'm a dumbass, I was using the wrong side of the plastic Cs-137 source. Normally is 10k cpm, reading the wrong side made it 2000 cpm. I've only been in this job for 8 months, and just changed site locations. At the old location the guy was doing the checks from the wrong side too, so when I first started working there I used the side that agreed with the historical data. I've corrected my check and noted why it was changed. Also I have made sure everyone I work with is on the same page.

Thanks!

Been there, done that - at one site, we actually marked wit "this side up" stickers on the edge... :o

I'll bet it never happens to you again..... ;D
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Offline SpyCat

ambient temperature
« Reply #14 on: Nov 20, 2013, 08:39 »
Good posts, good info here.  Yup, it's good a legacy to label/mark the response check geometry on the source or jig/holder.

Another thing to consider...For most styles of detector or meter, when the batteries get cold this will effect meter performance.  "If it's too cold for you, it's too cold for the meter."

For cold weather surveying, I advise techs to simply keep the meter indoors/warm until survey.  Here's my safety tip: If you're keeping extra batteries warm in your pocket, remove other items like keys or loose change.
 8)

atomicarcheologist

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Re: ambient temperature
« Reply #15 on: Nov 21, 2013, 08:46 »
Good posts, good info here.  Yup, it's good a legacy to label/mark the response check geometry on the source or jig/holder.

Another thing to consider...For most styles of detector or meter, when the batteries get cold this will effect meter performance.  "If it's too cold for you, it's too cold for the meter."

For cold weather surveying, I advise techs to simply keep the meter indoors/warm until survey.  Here's my safety tip: If you're keeping extra batteries warm in your pocket, remove other items like keys or loose change.
 8)
If you are working outside eight hours a day, you are going to lose significant time removing/replacing battteries. 

"If it's too cold for you...." is a great way to stay in the office, but will not get the job done. 

Us a VΩ meter to asssess batteries if you are concerned about the charge.  Using a professional grade battery will enhance your meter's functionality.

 


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