Reasons for DistoX going out of calibration

Duncan S

New member
At the EuroSpeleo surveying workshops there was discussion about how DistoX units occasionally go out of calibration.
Andrew Atkinson reported that although his does occasionally do this (so does mine), he'd not found any way to produce the problem under controlled conditions.

After one workshop, a Frenchman asked if I would mind my unit going out of calibration and he showed me how to do it.
The test was simple. Hold the Distox firmly down on the table and if the readings changed then the calibration had been upset.
What did he do?
Nothing more than rotate the springs in the base of the unit using a ball point pen  :eek:

Here's a photo showing the springs on my unit.
i-pXqFVNd-M.jpg


Note how the lanyard is wrapped around the spring.
If the lanyard causes rotation of the spring then the unit will go out of calibration!!!!!!!!!!

Also, I've just been washing my DistoX under the tap using a brush and I'm pretty sure the springs were moved while getting mud out from the springs. I've not re-checked the calibration but I won't be surprised if I find I need to re-calibrate at the start of my next surveying session.

Does anyone know if removing the springs with needle nose pliers is a good idea, or am I missing their purpose?
 

andrew

Member
Reasonably sure I do not have the springs on mine, but I have lent them out so cannot immediately check.

So if you leave the rotatable plate on, moving that would also take it out of calibration, unfortunately you need to do this to charge it. Although if it is not moved the springs should be held in the same position
 

Duncan S

New member
So you reckon it is a good idea to remove those springs?
Wanting a second opinion before I attack the unit  :)
 

maxf

New member
I removed the pins and the springs when I made mine, used silicon sealant to fill in the holes left behind
 

Benfool

Member
Hi Duncan

The springs are part of the end piece, which I removed when I made your distox - they serve no purpose now and I must of forgot to remove them! I'll make sure I remove them in the future if its screwing up the calibration!

B
 

ferret

New member
The springs are in indeed part of the end bracket, this i have removed along with its springs and sealed with outdoor grade silicon which seems to be the favoured method.
 

Goydenman

Well-known member
Even if you remove the springs there are still other reasons the Disto can go out of calibration. We calibrate it afresh before each trip. At first it was a pain to do this but now we are used to it and do it quickly.
 

Duncan S

New member
Thanks everyone!

@Goydenman - have you identified any causes for them going out of calibration?
Mine travelled to Spain and endured two long carries, 600m of SRT with many tight pitch heads and three nasty crawls and I was stunned to find the calibration check was OK. Going out of calibration seems rather random!
 

Goydenman

Well-known member
Duncan S said:
Thanks everyone!

@Goydenman - have you identified any causes for them going out of calibration?
Mine travelled to Spain and endured two long carries, 600m of SRT with many tight pitch heads and three nasty crawls and I was stunned to find the calibration check was OK. Going out of calibration seems rather random!

Yes seems quite random....not sure of why. Others have said when it gets banged about, batteries are moved (if the non-magnetic)..... but we have no evidence of what is really happening but on occasions found the calibration to be off
 
Duncan, as Goydenman has said above we calibrate every trip now as we have found to our cost that you can get a bit blase regarding calibration. It is so easy to assume you are okay which sometimes is true but then 3 hours into a survey trip is not the time to find out the calibration is off. As it is so easy to do at the start of each trip then why not do it and be sure. We tend to have certain spots in the caves we are currently resurveying to do the calibration and frequent use of these spots acctually makes it quicker still as you get to know your targets. Even in a tight grotty passage if you have a system it is still pretty quick to do.
You can of course do a rotation test to check your calibration at the start of the trip which should be the absolute minimum you do and you can of course do an occasional shot with rotation which will set calibration alarm bell ringing if the shot dosnt work. That was a good idea picked up at Eurospeleo.
I suspect we are telling our granny how to suck eggs here but as you talk to more people about this you here about lots of different theories and methods as to how things should be done. I like nice and simple, what we do works well.
As to why the calibration drops off then like others I can only speculate, maybe knocking the unit, local magnetic influence when storing the disto, geographic magnetic variations who knows, all I do know is that it does wander so to sure we calibrate and check every trip and now do not have to undergo those "I want to smash the disto to smithereens" moments when you realise the last several hours work is rubbish. Now if we could sort the occasional random Bluetooth conection, life would be stress free and perfect.

Nick
 

Rob

Well-known member
Swallowneck said:
...Now if we could sort the occasional random Bluetooth conection, life would be stress free and perfect...
Off topic slightly, but do you use TopoDroid instead of Pocket Topo? I find it more stable with the Bluetooth connection, and infinitely faster to reconnect if it is lost.
 

Duncan S

New member
I only have experience of TopoDroid on a Jeep Phone and have never had connection issues.
When my laser monkey has taken the Disto off up some nasty crawl I lose connection, but as soon as I regain line of sight within 20ft or less I thump download and it always has just worked.
 
Pocket Topo.
Usually fine once connected but for some reason it can be difficult to connect at start.
Now use this method which we fine works best.
Turn on PDA, let everything settle down then turn on BT. Then and only then turn on disto, waft it around a bit and hey presto connected.
Sometimes struggles with reconnect in body size tubes and round bends but a bit of swearing generally sorts this out.
 
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