Power Supply Units to GATSO cameras - update
Discussion
Following an allegation of 57mph on a 50mph dual carriageway, I have challenged my local constabulary on the basis of a complete lack of any maintenance schedule for the power supply unit within the GATSO cabinet.
Remember, that it is the camera module, that is moved from cabinet to cabinet, that is calibrated (in the Netherlands). Despite the fact that any other standards body would fall about laughing at the suggestion that a calibrated unit could be shipped across the North Sea, and then moved from site to site, and remain 'calibrated', you can't question GATSO calibration due to an earlier court ruling.
However, GATSO power supply units are not calibrated by my local constabulary - EVER (in over 10 years). The expert witness, who also works for the National Physical Laboratory setting standards for electronic measuring equipment, is under no doubt that it doesn't matter how well calibrated the camera module is, its accuracy cannot be guaranteed if the power supply hasn't been regularly checked.
Better still, it appears that the Constabulary is in breach of Health & Safety legislation (Electrical Equipment at Work). With officers routinely connecting camera modules into untested cabinets, it's only a matter of time before someone is electrocuted... the Police federation hasn't yet made a comment.
Any coppers out there know if their force's cabinet power supplies are tested?
Remember, that it is the camera module, that is moved from cabinet to cabinet, that is calibrated (in the Netherlands). Despite the fact that any other standards body would fall about laughing at the suggestion that a calibrated unit could be shipped across the North Sea, and then moved from site to site, and remain 'calibrated', you can't question GATSO calibration due to an earlier court ruling.
However, GATSO power supply units are not calibrated by my local constabulary - EVER (in over 10 years). The expert witness, who also works for the National Physical Laboratory setting standards for electronic measuring equipment, is under no doubt that it doesn't matter how well calibrated the camera module is, its accuracy cannot be guaranteed if the power supply hasn't been regularly checked.
Better still, it appears that the Constabulary is in breach of Health & Safety legislation (Electrical Equipment at Work). With officers routinely connecting camera modules into untested cabinets, it's only a matter of time before someone is electrocuted... the Police federation hasn't yet made a comment.
Any coppers out there know if their force's cabinet power supplies are tested?
Iused to have a bit of a sideline calibrating electrical and electronic equipment, and it is normal to specify that mains powered equipment is calibrated within mains power limits. It's quite common to find that the measurement precision of such equimpment varies considerably if the main supply varies by say +/- 10%.
Such equipment can be designed to minimize precision variations as a result of power supply changes, but another huge factor is temperature variation. Just think of the good old gatso stood on the end of a pole, in all weather.
I think it's highly unlikely that the precision of such equipment is good given all of the variables, but it is very much dependent on the equipment. The true way to sort this issue is to buy a standard gatso, and perform some proper testing.
A key way to establish if you're on to something here, is to ask the home office to show you the results of the scientific trials that have been done on such equipment, and demonstrate to you that they can scientifically vouch for the precision of their equipment to absolute standards given the wide variety of variables to which it is subjected.
Given the way the equipment works, I would predict that the biggest single source of error is within the frequency standard that the unit must use. Temperature and power supply quality, will have a significant effect on that. The actual measurement process will likely be quite robust within the constraints of the frequency standard. Once the measurement has been made, it's thresholding, will also be subject to temperature and power supply variations, unless the unit makes digital cmparisons.
Such equipment can be designed to minimize precision variations as a result of power supply changes, but another huge factor is temperature variation. Just think of the good old gatso stood on the end of a pole, in all weather.
I think it's highly unlikely that the precision of such equipment is good given all of the variables, but it is very much dependent on the equipment. The true way to sort this issue is to buy a standard gatso, and perform some proper testing.
A key way to establish if you're on to something here, is to ask the home office to show you the results of the scientific trials that have been done on such equipment, and demonstrate to you that they can scientifically vouch for the precision of their equipment to absolute standards given the wide variety of variables to which it is subjected.
Given the way the equipment works, I would predict that the biggest single source of error is within the frequency standard that the unit must use. Temperature and power supply quality, will have a significant effect on that. The actual measurement process will likely be quite robust within the constraints of the frequency standard. Once the measurement has been made, it's thresholding, will also be subject to temperature and power supply variations, unless the unit makes digital cmparisons.
Edited by dilbert on Monday 24th September 19:51
This from an earlier post by another contributor:
"gatso equipment uses SMPSU's - switch mode power suply units.
SMPSU's couldn't give a flying s***e what the input voltage is like, as long as it's somewhere between 55v and 400v, with a brown out tollerence interval of (I think) at least 2 seconds. Loop resistance is also irrelevent, as long as it can supply the required VA, which is only about 200. Basically the loop resistance would have to be greater than about 40-50 ohms to affect the operation of the camera.
the output will be an absolutely rock solid 5v, 12v and -12v. Similar to a computer power supply."
What this misses is that if the power supply unit is never tested, there is no way of substantiating that the unit's output is within the specified range of tolerance. There is also the matter of reliability of these units. Some would have you believe that they are rock-solid. My own experience in corporate I.T. tells me that the output, even with carefully monitored input, can vary substantially. Indeed, there is an entire industry in I.T. monitoring power supply output, particularly to expensive server processor boards. Hot redundant power supplies exist not just for back-up on total failure, but to switch, if the output strays outside of its prescribed range.
Remember too that GATSO camera modules are calibrated on a stable, laboratory power supply.
Whilst I'm sure that the Crown can rely upon DCA to lean heavily on the Judge in a preliminary hearing to decide whether or not the expert evidence is admissible, the fact remains that CPS and the constabulary don't have an answer to this. In response to a disclosure request, CPS have declined to provide any Home Office specifications, and have even refused to forward the 'Speedmeter Handbook' referred to in the calibration certificate.
In the words of the Head of the Saftey Camera Unit, "No, we've never tested them. Nobody's ever asked that question before..."
"gatso equipment uses SMPSU's - switch mode power suply units.
SMPSU's couldn't give a flying s***e what the input voltage is like, as long as it's somewhere between 55v and 400v, with a brown out tollerence interval of (I think) at least 2 seconds. Loop resistance is also irrelevent, as long as it can supply the required VA, which is only about 200. Basically the loop resistance would have to be greater than about 40-50 ohms to affect the operation of the camera.
the output will be an absolutely rock solid 5v, 12v and -12v. Similar to a computer power supply."
What this misses is that if the power supply unit is never tested, there is no way of substantiating that the unit's output is within the specified range of tolerance. There is also the matter of reliability of these units. Some would have you believe that they are rock-solid. My own experience in corporate I.T. tells me that the output, even with carefully monitored input, can vary substantially. Indeed, there is an entire industry in I.T. monitoring power supply output, particularly to expensive server processor boards. Hot redundant power supplies exist not just for back-up on total failure, but to switch, if the output strays outside of its prescribed range.
Remember too that GATSO camera modules are calibrated on a stable, laboratory power supply.
Whilst I'm sure that the Crown can rely upon DCA to lean heavily on the Judge in a preliminary hearing to decide whether or not the expert evidence is admissible, the fact remains that CPS and the constabulary don't have an answer to this. In response to a disclosure request, CPS have declined to provide any Home Office specifications, and have even refused to forward the 'Speedmeter Handbook' referred to in the calibration certificate.
In the words of the Head of the Saftey Camera Unit, "No, we've never tested them. Nobody's ever asked that question before..."
ramtec said:
Unchecked power = reasonable doubt...
You are forgetting than in the case of speed enforcement the notion of reasonable doubt is tossed out of the window like a soggy tissue. While we have a criminal justice system for most offences we have a farce for speed enforcement that has no basis in the corner stones of justice or evidence. 
ramtec said:
"did you do the speed or not?"
Absolutely not.
I was driving a particularly short wheel-based, high-backed vehicle,so my suspicions were immediately aroused by the GATSO reading. However, because of a previous judgement, the GATSO calibration is 'unchallengable'.
That seems a bit unreasonable. It's almost like saying that, legally, the camera is unable to fall out of calibration. The thing is that scientifically, that's wrong. Absolutely not.
I was driving a particularly short wheel-based, high-backed vehicle,so my suspicions were immediately aroused by the GATSO reading. However, because of a previous judgement, the GATSO calibration is 'unchallengable'.
Pragmatically even, it's wrong.....
There is a whole industry (although admittedly the accountants are trying to sell it to china) based around the regular calibration of well looked after scientific equipment. For Brown's sake, industry looks after it's measuring equipment. The government sticks it on a pole at the side of the road, where people attack it with burning tyres!
I suppose, legally, if it's capable of raping someones wallet, then it's properly calibrated.
Edited by dilbert on Tuesday 25th September 07:45
skymaster said:
ramtec said:
Unchecked power = reasonable doubt...
You are forgetting than in the case of speed enforcement the notion of reasonable doubt is tossed out of the window like a soggy tissue. While we have a criminal justice system for most offences we have a farce for speed enforcement that has no basis in the corner stones of justice or evidence. Anyone know if ANY forces check power supplies? £70 for an annual test to prevent your officers from being electrocuted - any takers?
Dwight VanDriver said:
I would have thought it would be standard practice on shifting the 'box' to another location that a couple of runs with a vehicle with known accurate speedo would be made?????????????????
dvd
Even if they carried out your suggested actions, it wouldn't be enough.dvd
The standard line taken in court by the Crown is that police officers 'test' the camera modules each time they fit them in a new location. The 'test' is rarely questioned but is couched in such terms as to make the Court believe that it confirms accuracy. This is grossly misleading. Suffice to say that its's nothing remotely connected to calibration at all. It's a very basic 'does it work?' test. Pretty close to a conspiracy to pervert the course of justice, with a theoretical maximum penalty of life imprisonment.
When I told the MD of one of the UK's largest aerospace 'testing' companies, that GATSO camera modules were calibrated in the Netherlands, then shipped back to the UK, then moved from cabinet to cabinet between calibrations, he fell off his perch. He went on to explain that if the aerospace industry calibrated measuring equipment like that, not only would it be disallowed, but they would be prosecuted.
Any one know if ANY forces check their GATSO power supplies...?
When I told the MD of one of the UK's largest aerospace 'testing' companies, that GATSO camera modules were calibrated in the Netherlands, then shipped back to the UK, then moved from cabinet to cabinet between calibrations, he fell off his perch. He went on to explain that if the aerospace industry calibrated measuring equipment like that, not only would it be disallowed, but they would be prosecuted.
Any one know if ANY forces check their GATSO power supplies...?
ramtec said:
Unchecked power = reasonable doubt...
I think you've got a point, quite possibly a technically very valid point. It needs to be tested in court. Whether the exposure will produce a result I don't know but I wish you luck taking, on face value, what you say that you were NOT travelling OPL.All I can add is that in one place I used to frequent when we threw the full load onto some particularly juicy electrical kit the management at the local Somerfield used to have the dubious pleasure of facing a row of customers part way through the check out who then had to unpack everything and have it all scanned again as the tills had all tripped out and needed to be knocked off and rebooted. They weren't next door either.
On another completely tangential thought, we know that when operating the hand held devices the operators have to have mobiles and comms units turned off or be set appropriately. Are cameras shielded from other transmissions? Both hand held and roadside?
I ask because of recalling some kit which used to trip out whenever the local FB turned out on a shout and their radio transmissions were picked up by parts of the controller network of this equipment. Took us ages to find out what the problem was, but we got some complete trips, and some dodgy results which were obviously dodgy. How many wrong but not obviously dodgy results I have not the first clue to be honest. Ponders.
Dwight VanDriver said:
I would have thought it would be standard practice on shifting the 'box' to another location that a couple of runs with a vehicle with known accurate speedo would be made?????????????????
Errr, hang on just one second. You mean they'd deliberately drive past at a known dangerous(tm) speed just to test it out?How can they possibly do this then go ahead and charge a member of public 60 quid and three points for doing the exact same thing? Hmmmm?
SM
Edited by supermono on Tuesday 25th September 15:41
Edited by supermono on Tuesday 25th September 15:42
The surprising thing is how easy this would have been to get right. A few quid each year, and you could vouch for the output voltage and the cabinet circuitry resistance AND meet your statutory obligations in keeping police officers safe.
The fact that it appears, so far, that no forces are testing power supplies, suggests that it was never in the original spec, and that in certifying the GATSO, the Home Office needs to be called to account.
My local constabularly haven't testsed a single power supply in over ten years. They allege, but cannot substantiate, that there's no need to test power supplies. On that logic, officers could be fitting camera modules to untested cabinet power supplies when the units are 25+ years old. I'd buy some rubber gloves, if I were you...
The fact that it appears, so far, that no forces are testing power supplies, suggests that it was never in the original spec, and that in certifying the GATSO, the Home Office needs to be called to account.
My local constabularly haven't testsed a single power supply in over ten years. They allege, but cannot substantiate, that there's no need to test power supplies. On that logic, officers could be fitting camera modules to untested cabinet power supplies when the units are 25+ years old. I'd buy some rubber gloves, if I were you...
Edited by ramtec on Tuesday 25th September 16:08
Edited by ramtec on Tuesday 25th September 16:08
Seeing as the Gatso was developed to photograph a rally car mid corner, why has no-one (to my knowledge) purchased on for 'personal' use, which would enable it to be tested? The purchase could no doubt be disguised? I guess the same question also applies for the LTI 20:20 Dodgyscope?
Flat in Fifth said:
ramtec said:
Unchecked power = reasonable doubt...
I think you've got a point, quite possibly a technically very valid point. It needs to be tested in court. It's an interesting idea to "attack" the credibility of the power supply (which is seemingly dubious - although one poster suggests it's fine and dandy, even though it's never tested).
If nothing else, Shirley this is a breach of Health and Safety reg's? A breach that would cost MILLIONS to deal with each year? Perhaps a better way to attack scameras (tyres, blowtorch, sorry...) - would be a complaint to the HSE?
To the OP - your profile says East Midlands, are you Notts way?
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