In view of our damp issue we are seriously considering buying a good damp meter preferably the Protimeter but at £132 it is difficult to justify the purchase. Not really interested in purchasing a cheapo B& Q special as wouyld prefer something more acceptable. Any suggestions? Thanks.
Alternative to Protimeter
- Thread starter Surfer
- Start date
We have found a no contact moisture meter CEM DT 128 which seems to be able to detect damp below the surface.
Hello Surfer,
I have reviewed the operating instructions for the CEM DT 128 which are published on line.
The first point of concern I have about the instruments suitability for testing the moisture content in caravan construction, relates the the instruments stated method of measurement. It uses a high frequency pulse to excite the material under test. It then listens to the materials response and interprets the 'echo' in some way. Its rather like an ultra sound (US) scanner used in hospitals, but far less sophisticated.
Essentially the moisture content of a material will increase the materials US conductivity. Air pockets diminish the US conductivity.
They go on to tell us the device will project US and interrogate materials at a depth of between 20 to 40mm. That is substantially deeper than the thickness of caravan wall boarding. I suspect it will not handle thin materials very well as the distance and thus the time between the emission and the reflected energy being received by the ball will be too short for it to resolve the signal.
They tell us to avoid materials with metal foils. Some caravan wall baoding has metal foils.
They tell us the results it produces will vary dependant on the material being tested, thus it seems a true 15% moisture content will give different readings for different materials.
It makes no mention of whether it can adequately resolve moisture content of composite constructions. Caravan walls are composites, with layers of very different materials.
They state that the values the instrument produces are "indicative and not binding"
It goes on to tell you that "The conclusions to be drawn from the results of measurements made by each user depend on the individual circumstances and his experience gained from professional practice"
On the basis of what I know and have read, I cannot conclude this device will provide any real confidence in looking for moisture in a caravan. There are too many variables affecting its operation.
It may have a place on a large building site, where a competent user needs to check large quantities, but for infrequent use on thin materials I can see its results being open too much inconclusive debate.
I have reviewed the operating instructions for the CEM DT 128 which are published on line.
The first point of concern I have about the instruments suitability for testing the moisture content in caravan construction, relates the the instruments stated method of measurement. It uses a high frequency pulse to excite the material under test. It then listens to the materials response and interprets the 'echo' in some way. Its rather like an ultra sound (US) scanner used in hospitals, but far less sophisticated.
Essentially the moisture content of a material will increase the materials US conductivity. Air pockets diminish the US conductivity.
They go on to tell us the device will project US and interrogate materials at a depth of between 20 to 40mm. That is substantially deeper than the thickness of caravan wall boarding. I suspect it will not handle thin materials very well as the distance and thus the time between the emission and the reflected energy being received by the ball will be too short for it to resolve the signal.
They tell us to avoid materials with metal foils. Some caravan wall baoding has metal foils.
They tell us the results it produces will vary dependant on the material being tested, thus it seems a true 15% moisture content will give different readings for different materials.
It makes no mention of whether it can adequately resolve moisture content of composite constructions. Caravan walls are composites, with layers of very different materials.
They state that the values the instrument produces are "indicative and not binding"
It goes on to tell you that "The conclusions to be drawn from the results of measurements made by each user depend on the individual circumstances and his experience gained from professional practice"
On the basis of what I know and have read, I cannot conclude this device will provide any real confidence in looking for moisture in a caravan. There are too many variables affecting its operation.
It may have a place on a large building site, where a competent user needs to check large quantities, but for infrequent use on thin materials I can see its results being open too much inconclusive debate.
Thanks John for the valued input as it makes sense to me for a change. I have been watching Protimeters on eBay and second hand they are going for over £100 although a brand new one delivered costs £132.
As per our damp episode I want a damp meter that is as good as the dealer's damp meter so they cannot argue the toss as I cannot see how there can be a difference of 17% difference between the mobile tech's and the dealers readings.
Either way "anything of 30% may involved structutal damage or invariably deterioration" and those are the words printed on the dealer's damp check sheet. The workshop foreman was trying to make out as if 43% is not that serious!
As per our damp episode I want a damp meter that is as good as the dealer's damp meter so they cannot argue the toss as I cannot see how there can be a difference of 17% difference between the mobile tech's and the dealers readings.
Either way "anything of 30% may involved structutal damage or invariably deterioration" and those are the words printed on the dealer's damp check sheet. The workshop foreman was trying to make out as if 43% is not that serious!
Hello Surfer,
If you need to challenge a result of a measurement in cases like yours, then its much simpler to provide like for like measurement methods to minimise variables that could be used to frustrate the claim processes.
Protometers are expensive to buy, :- They need to be calibrated regularly to ensure reliable results For evidence in the evnt of a court case, the meter may need to be calibrated against national standards which is likley to cost at least £25 per calibration..
I'm guessing that it will be cheaper to have your mobile caravan mechanic do a regular check when he services your van, than for you to buy a Protometer, and to keep it calibrated.
If you need to challenge a result of a measurement in cases like yours, then its much simpler to provide like for like measurement methods to minimise variables that could be used to frustrate the claim processes.
Protometers are expensive to buy, :- They need to be calibrated regularly to ensure reliable results For evidence in the evnt of a court case, the meter may need to be calibrated against national standards which is likley to cost at least £25 per calibration..
I'm guessing that it will be cheaper to have your mobile caravan mechanic do a regular check when he services your van, than for you to buy a Protometer, and to keep it calibrated.
Prof John L said:
The Protimeters are self calibrated each use, they come with a tool to carry the calibration out.
Page 8 Protimeter Surveymaster
8 Instrument Calibration Check
A calibration check device (Calcheck) is supplied with the
Surveymaster for checking the Measure mode calibration.
Perform the calibration check as follows:
1.Hold the Calcheck across the electrode pins as shown at the right.
A correctly calibrated Surveymaster will read18.2±1.0
.
2.If the instrument reading is incorrect, contact
your supplier for further instructions.
3.Check the Search mode operation by holding
the instrument against a reference wall that is
assumed to be in a stable condition and that
does not have any pipes or wires running
through it.
4.Note and record the relative value that is displayed.
5.Check the instrument at the same position on the reference
wall at regular intervals.
6.Contact your supplier if the reading varies by more than
±50 from the original reference value.
Thanks. Our mobile technician uses the Survey version but it would be a bit of an overkill for us. The cost to get the caravan damp checked is about £35 - £60 so if you want it done twice a year, it works out cheaper to buy the Protimeter Mini.
If we had done this in the past year, maybe the damp damage would not have been so bad and we would have been able to show that the dealer never carried out a proper damp check as it was probably left to an "appy".
As said front panel can be changed, but floor???
If we had done this in the past year, maybe the damp damage would not have been so bad and we would have been able to show that the dealer never carried out a proper damp check as it was probably left to an "appy".
As said front panel can be changed, but floor???
Thanks, Proff for doing all the research on this device and publishing it so clearly. I was working my way down the thread and immediatly made a note to dig it all out.
I also agree with your comments about the probably utility of the device. I can see a good use for the technique for monitoring material being produced say a board or powder where you could do an off-line calibration at the start of the run and use this device or similar to show variation, but not for absolute measurement.
I am also a little suspicious of the calibration check device for the Protimeter; in my experience (admittedly a few years old) the only reliable way was to weigh, dry and reweigh a sample.
I also agree with your comments about the probably utility of the device. I can see a good use for the technique for monitoring material being produced say a board or powder where you could do an off-line calibration at the start of the run and use this device or similar to show variation, but not for absolute measurement.
I am also a little suspicious of the calibration check device for the Protimeter; in my experience (admittedly a few years old) the only reliable way was to weigh, dry and reweigh a sample.
Martin_E said:
Hello Martin,
I am aware of Protometers self calibration check. And despite what you have reproduced, my statement still stands for the following reason:- How do you know the proving ('calibration') piece is accurate?
I can think of no practical (i.e. usable in the field) proving device that is absolutely incorruptible. Consequently calibration under controlled conditions is the only way of establishing the known error of any device.
For example engineers will often use a gauge or proving device for confirming the consistency of products, but these have to be periodically calibrated to ensure conformity. Evidence of calibration will usually require a calibration record produced by a UKAS or equivalent test house.
UKAS or equivalent test houses will have systems with determined accuracy traceable to National or International standards.
OK the chances are the local proving device is within specification, but there is also a chance its not, Perhaps its been damaged, or worn out or even tampered with. The point is how can you show its withing manufactures specifications? That's what true calibration determines, it describes the degree of uncertainty a device has.
In addition and especially with moisture content meters, any difference or errors in the technique used to make the measurement will create differences in the outcome.
Where a comparison between measurements of the same measureand is being made, it is imperative the accuracy of two measurement devices and the methods used is known. Readings from un-calibrated test gear would be torn to shreds by any good barrister.
Prof, you've done it again ! As a past President of the Institute of Measurement and Control, please accept my warmest congratulations.
Thank you Ray,
As you will know I have only described and explained basic quality assurance procedures as required by ISO9000 etc and any self respecting engineer.
I could have expanded about the unreliability of only using a single value as a method of calibration, which only established the error at that value, it does not prove the linearity, bias, or skew across the range of the instrument, or any other sources of uncertainty factors.
Any Jobs going?
I'm still of the opinion that its not worth an individual caravanner purchasing and maintaining a moisture meter of the same class as a professional to only make two or three surveys a year with the intention of trying to challenge the accuracy of dealer measurement values.
Being slight more helpful, the purchase of a very low cost model which hopefully will alert the owner to any readings of concern, which then prompts getting a professional survey carried out to accurately assess the situation will almost certainly be more cost effective.
As you will know I have only described and explained basic quality assurance procedures as required by ISO9000 etc and any self respecting engineer.
I could have expanded about the unreliability of only using a single value as a method of calibration, which only established the error at that value, it does not prove the linearity, bias, or skew across the range of the instrument, or any other sources of uncertainty factors.
Any Jobs going?
I'm still of the opinion that its not worth an individual caravanner purchasing and maintaining a moisture meter of the same class as a professional to only make two or three surveys a year with the intention of trying to challenge the accuracy of dealer measurement values.
Being slight more helpful, the purchase of a very low cost model which hopefully will alert the owner to any readings of concern, which then prompts getting a professional survey carried out to accurately assess the situation will almost certainly be more cost effective.
Not sure how any damp issue can be cost effective, but understand what you are saying? As I no longer trust the dealer when we eventually collect the caravan, we will have another damp test done and if it proves negative, we will reject the caravan and claim the cost of the test from the dealer.Prof John L said:
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