I've been nicked but do I have a defence ?

[Harry H]

Just been notified that I've be caught doing 49 in a 40 on a dual carriage way.

By logging on to the website I can see the photos and the calibration certificate. It very helpfully also gives the distance at which I was photo'd at of 174 meters.

Yet when looking at the calibration certificate it would appear that distance checks for the equipment are at 25/75/100 meters. Does that mean it isn't reliable at 174 meters and I've got a case for defence or is it just wishfull thinking on my part ?

[SS2.]

Exceptionally wishful thinking ..

[IanG1]

I would ask if they can prove the equipment has an accurate usable range at the 174 meters you were clocked at? Worth a punt in my opinion.

[donkmeister]

Teletraffic UK have a website with instruction manuals of all their products (originally made by Laser Technology Inc). Maximum approved distances are on those, I'd be very surprised if any are under 174m though!

Good luck though, trying it may get you put on the "pain the backside, don't bother" pile.

[sim72]

Very wishful, as it's a laser device its range will be 300m at the least.

[bigandclever]

Since we’re being optimistic, it’s been getting less accurate on the speed simulation tests over the years.

[Repel_Max]

The 3 distance checks in the calibration process allows the device to be certified as accurate in distance to its full range of 1000m.

This is a speedmeter though so you should look at the speed accuracy. The speed checks on the certificate allow the device to be used throughout its speed range -299mph>0mph>299mph

So no, you don't have a defence based upon your OP. You're welcome.

[BertBert]

Repel_Max said:

The 3 distance checks in the calibration process allows the device to be certified as accurate in distance to its full range of 1000m.

As the OP says, the distance check only goes up to 100m. How does that show the device is accurate at 1000m? Not suggesting that the OP has any chance at all, just curious.
Bert

[blank]

I wonder how well that calibration process would stand up to an ISO17025 audit...

[Truffs]

Well it obviously would not but that’s not important. What is important is that the OP helps the coffers of the nation and pays promptly with minimum of fuss.

The country needs more like him or society cannot afford the costs of itself.

I would like the fines to be spent on filling in the pot holes then we can go faster with less risk and pay more in fines for the privilege. Better for society that way and we can be more like Finland.

[Repel_Max]

BertBert said:

Repel_Max said:

The 3 distance checks in the calibration process allows the device to be certified as accurate in distance to its full range of 1000m.

As the OP says, the distance check only goes up to 100m. How does that show the device is accurate at 1000m? Not suggesting that the OP has any chance at all, just curious.
Bert

It shows the linearity of the device.

As far as I am aware, distance doesn’t matter for a speed reading. Why would it?

[Repel_Max]

blank said:

I wonder how well that calibration process would stand up to an ISO17025 audit...

It would pass as long as it was traceable. Why wouldn’t it?

[BertBert]

Repel_Max said:

It shows the linearity of the device.

As far as I am aware, distance doesn’t matter for a speed reading. Why would it?

Well I would have thought that the laser gun can't work over infinite distances. The beam will spread, the gun won't be accurate to aim, the beam won't be made strong enough to reach to the moon and back etc.
But if it generally has a working range greater than 1000m and the test is only to establish linearity at the bottom end of that and that satisfies the approval mechanism, then that's fine.
But as a general case showing that a remote sensing device works at 1/0th of its working range wouldn't be taken as proof that it works over that range.
Bert

[blank]

Repel_Max said:

blank said:

I wonder how well that calibration process would stand up to an ISO17025 audit...

It would pass as long as it was traceable. Why wouldn’t it?

Because it probably isn't traceable, doesn't appear to have been calibrated over its full range, and doesn't look to have any uncertainty statements.

[Repel_Max]

BertBert said:

Repel_Max said:

It shows the linearity of the device.

As far as I am aware, distance doesn’t matter for a speed reading. Why would it?

Well I would have thought that the laser gun can't work over infinite distances. The beam will spread, the gun won't be accurate to aim, the beam won't be made strong enough to reach to the moon and back etc.
But if it generally has a working range greater than 1000m and the test is only to establish linearity at the bottom end of that and that satisfies the approval mechanism, then that's fine.
But as a general case showing that a remote sensing device works at 1/0th of its working range wouldn't be taken as proof that it works over that range.
Bert

Unless you know how it works and can determine that a check on 1/10th of the range will certify its full range.

Lasers are used to check the distance to the moon and the divergence of the laser beam facilitates that. The wide beam allows the aim to be approximate and illuminates a retro-refelctive target placed there by the Apollo missions. Similarly, the divergence of the beam of the speedmeter faciliates targeting because only the retro-reflective objects on the target are significant.

It always helps when you know your subject...what's your's? Clearly it is not laser measuring equipment.

[Repel_Max]

blank said:

Repel_Max said:

blank said:

I wonder how well that calibration process would stand up to an ISO17025 audit...

It would pass as long as it was traceable. Why wouldn’t it?

Because it probably isn't traceable, doesn't appear to have been calibrated over its full range, and doesn't look to have any uncertainty statements.

OK. Thankfully you are not making the decisions on this calibration.

[blank]

Repel_Max said:

blank said:

Repel_Max said:

blank said:

I wonder how well that calibration process would stand up to an ISO17025 audit...

It would pass as long as it was traceable. Why wouldn’t it?

Because it probably isn't traceable, doesn't appear to have been calibrated over its full range, and doesn't look to have any uncertainty statements.

OK. Thankfully you are not making the decisions on this calibration.

I'm just saying it would be interesting to audit the whole speed measurement and calibration process (do they correct for angle for instance?). I bet there's at least a couple of mph uncertainty either way if you take the whole chain into account. Maybe that's why they tend to allow 10% grace.

[Repel_Max]

blank said:

Repel_Max said:

blank said:

Repel_Max said:

blank said:

I wonder how well that calibration process would stand up to an ISO17025 audit...

It would pass as long as it was traceable. Why wouldn’t it?

Because it probably isn't traceable, doesn't appear to have been calibrated over its full range, and doesn't look to have any uncertainty statements.

OK. Thankfully you are not making the decisions on this calibration.

I'm just saying it would be interesting to audit the whole speed measurement and calibration process (do they correct for angle for instance?). I bet there's at least a couple of mph uncertainty either way if you take the whole chain into account. Maybe that's why they tend to allow 10% grace.

It is interesting, you are correct.
Would teh calibration process stand up to ISO17025? Yes
Just because your knowledge of the instrument and calibration process matches your username doesn't mean it can't.

[Getragdogleg]

How would the operator have "formed a prior opinion" of the speed so they can then use the equipment to check at 174 m ?

[BertBert]

Repel_Max said:

Unless you know how it works and can determine that a check on 1/10th of the range will certify its full range.

Lasers are used to check the distance to the moon and the divergence of the laser beam facilitates that. The wide beam allows the aim to be approximate and illuminates a retro-refelctive target placed there by the Apollo missions. Similarly, the divergence of the beam of the speedmeter faciliates targeting because only the retro-reflective objects on the target are significant.

It always helps when you know your subject...what's your's? Clearly it is not laser measuring equipment.

Dude why do you argue like an arse all the time? Your first point is exactly the same as I made. And as it's so good, will that speed gun measure the speed of cars at the distance of the moon? Clearly it can't because it couldn't aim at a car that far away.
Bert