LTI 20-20 UltraLyte 100 Calibration checks
Discussion
tapereel said:
cptsideways said:
tapereel said:
Well as you say, you are not an expert on speed guns. You do mention that you have expertise on a related subject but because you are not an expert in overcoming the inherent faults/inaccuracies in that technology you dispute a technology you admit to being inexpert in.
I am not minded or motivated to educate you in speedmeter technology but I will point out that ignorance of something is not justification that it isn't possible, real or accurate.
As you are expert in optical distance measuring devices and its inherent issues then all you need to do is to overcome those issues and you will be able and expert in optical speedmeters. The problem you have is that you need to become more expert in the subject you profess to be expert in.
Good luck.
Unfortunately for you a speedmeter as you put it is A: a distance measuring device to start with, B: it then from those distance & time, then does a few calculations/guesstimates & makes a number up = C. I am not minded or motivated to educate you in speedmeter technology but I will point out that ignorance of something is not justification that it isn't possible, real or accurate.
As you are expert in optical distance measuring devices and its inherent issues then all you need to do is to overcome those issues and you will be able and expert in optical speedmeters. The problem you have is that you need to become more expert in the subject you profess to be expert in.
Good luck.
If you are familiar with part A's foibles in many different fields its not hard to work out multiplying A's foibles x B does not always = C accurately every time !
If you would like a demonstration I'd be happy to oblige
PS I may have a little bit of experience on the subject
tapereel said:
Monty Python said:
The way I understand it is that the "speed gun" isn't really a "speed gun" at all - it's a distance measuring device. It works by measuring the distance to the vehicle twice a set time apart and uses that to calculate your speed. To calibrate it all you need to do is measure a series of stationary objects a known distance away and that's it, hence the reason why you don't need moving objects.
For example, if you measure the distance to a vehicle, then repeat a second later and the distance has changed by 16.67m then you can easily calculate the speed to be 60km/h.
MontyFor example, if you measure the distance to a vehicle, then repeat a second later and the distance has changed by 16.67m then you can easily calculate the speed to be 60km/h.
You should stick to comedy...OK you have.
The speedometer doesn't work like that.
The speed gun really is a speed gun, it measures and indicates distance only after the speed has been measured.
Perhaps it is more accurate to say "the speed gun isn't a distance gun, it's a speed gun that can also measure distance."
What fun.
Let me give you a clue, they measure distances over time. Which is partly why they are inaccurate as the distance part is the difficult bit with moving targets.
Monty Python said:
You're quite correct - anything that measures distance by light can be affected by all manner of issues caused by reflection, refraction, absorption, scattering and a bunch of other processes.
Temperature, air pressure & weather also have an effect- light rain is a worse problem than heavy rain for some strange reason.tapereel: I'm curious as to why speed measurement doesn't require distance measurement- care to 'educate' me?
Rovinghawk said:
Temperature, air pressure & weather also have an effect- light rain is a worse problem than heavy rain for some strange reason.
tapereel: I'm curious as to why speed measurement doesn't require distance measurement- care to 'educate' me?
Hint - the clue is in the unit of measurement.tapereel: I'm curious as to why speed measurement doesn't require distance measurement- care to 'educate' me?
From the Manual.
Sensors
The UltraLyte has two lenses on the front panel. The top lens transmits infrared LASER signals;
the bottom lens receives signals back from the target and feeds signal information to the internal
circuitry.
The internal circuitry consists of a LASER range Sensor, timing, analysis, computation and
display circuits.
The UltraLyte determines distance through its LASER range sensor by measuring the time of
flight of short pulses of infrared light. The UltraLyte has a broad spectrum of sensitivity and can
work with both reflective and non-reflective targets.
The maximum measurement distance varies with target and environmental conditions.
The absolute maximum is approximately 610 metres.
Sensors
The UltraLyte has two lenses on the front panel. The top lens transmits infrared LASER signals;
the bottom lens receives signals back from the target and feeds signal information to the internal
circuitry.
The internal circuitry consists of a LASER range Sensor, timing, analysis, computation and
display circuits.
The UltraLyte determines distance through its LASER range sensor by measuring the time of
flight of short pulses of infrared light. The UltraLyte has a broad spectrum of sensitivity and can
work with both reflective and non-reflective targets.
The maximum measurement distance varies with target and environmental conditions.
The absolute maximum is approximately 610 metres.
tapereel said:
Monty
You should stick to comedy...OK you have.
The speedometer doesn't work like that.
The speed gun really is a speed gun, it measures and indicates distance only after the speed has been measured.
Perhaps it is more accurate to say "the speed gun isn't a distance gun, it's a speed gun that can also measure distance."
What fun.
Congratulations, tapereel, this is exactly incorrect. You should stick to comedy...OK you have.
The speedometer doesn't work like that.
The speed gun really is a speed gun, it measures and indicates distance only after the speed has been measured.
Perhaps it is more accurate to say "the speed gun isn't a distance gun, it's a speed gun that can also measure distance."
What fun.
WinstonWolf said:
I'd love to see how our resident eel describes speed without first knowing distance and time...
Well, there are people around who believe it's possible to change speed without also changing at least one of the other two, which is a bit odd given that they seem to recognise that it's impossible to change any of the other two either in a given situation.Edited by Pete317 on Tuesday 24th November 16:10
tapereel said:
Well as you say, you are not an expert on speed guns. You do mention that you have expertise on a related subject but because you are not an expert in overcoming the inherent faults/inaccuracies in that technology you dispute a technology you admit to being inexpert in.
I am not minded or motivated to educate you in speedmeter technology but I will point out that ignorance of something is not justification that it isn't possible, real or accurate.
As you are expert in optical distance measuring devices and its inherent issues then all you need to do is to overcome those issues and you will be able and expert in optical speedmeters. The problem you have is that you need to become more expert in the subject you profess to be expert in.
Good luck.
Well, it seems quite evident that you're no expert on speed guns either - in fact I've seen nothing to suggest that you might even have a clue.I am not minded or motivated to educate you in speedmeter technology but I will point out that ignorance of something is not justification that it isn't possible, real or accurate.
As you are expert in optical distance measuring devices and its inherent issues then all you need to do is to overcome those issues and you will be able and expert in optical speedmeters. The problem you have is that you need to become more expert in the subject you profess to be expert in.
Good luck.
If you reckon you know how speed guns work then how about trying to explain it to us? Or perhaps even point us to some literature which explains it?
A speed gun could measure the changing phase lag between transmitted and received light pulses. By assuming a constant velocity of light the rate of change of lag is equal to the rate of change of distance that the light has travelled. This is equal to the rate of change of distance in the direction of the light pulse. So, the measurement of speed could be done without explicitly measuring distance.
Speed could also be measured by recording the doppler shift of the light.
Edit for typo.
Speed could also be measured by recording the doppler shift of the light.
Edit for typo.
Edited by V8LM on Tuesday 24th November 17:02
V8LM said:
A speed gun could measure the changing phase lag between transmitted and received light pulses. By assuming a constant velocity of light the rate of change of lag is equal to the rate of change of distance that the light has travelled. This is equal to the rate of change of distance in the direction of the light pulse. So, the measurement of speed could be done without explicitly measuring distance.
Speed could also be measured by recording the doppler shift of the light.
Edit for typo.
It *could* do a number of things, but I don't think the debate is about how it *could* measure speed, rather how it *does* do it.Speed could also be measured by recording the doppler shift of the light.
Edit for typo.
OK boys and girls, here's a puzzle for you all to ponder.
The distance accuracy is dependent upon the rate at which the internal clock oscillates. If it is exactly as designed the distance and speed will read correctly.
If the internal clock slows of speeds up or varies from the designed rate the distance reading will either be too short or too long because the clock rate in the distance formula will be other than the predetermined rate. The speed reading however will be exactly right no matter what the clock rate is.
Work that out and you will know how the device works and why the absolute distance is not used in the speed calculation.
Crack on with that and I will drop by in a month or two to see if there is any expertise in speed guns on here but me.
Pip-pip
The distance accuracy is dependent upon the rate at which the internal clock oscillates. If it is exactly as designed the distance and speed will read correctly.
If the internal clock slows of speeds up or varies from the designed rate the distance reading will either be too short or too long because the clock rate in the distance formula will be other than the predetermined rate. The speed reading however will be exactly right no matter what the clock rate is.
Work that out and you will know how the device works and why the absolute distance is not used in the speed calculation.
Crack on with that and I will drop by in a month or two to see if there is any expertise in speed guns on here but me.
Pip-pip
Edited by tapereel on Tuesday 24th November 17:32
FurtiveFreddy said:
It *could* do a number of things, but I don't think the debate is about how it *could* measure speed, rather how it *does* do it.
I was pointing out that speed can be measured without explicitly measuring distance. The LTI measures speed by recording the time for a number (60 for some devices) of 4 ns light pulses to be returned. Speed towards the device is calculated as the rate at which these echo-times decrease. 75% of the echoes have to be valid (i.e. their return time has to be within 1.3 ns of when it should have been for the calculated speed) in order for the device to give a reading.tapereel said:
OK boys and girls, here's a puzzle for you all to ponder.
The distance accuracy is dependent upon the rate at which the internal clock oscillates. If it is exactly as designed the distance and speed will read correctly.
If the internal clock slows of speeds up or varies from the designed rate the distance reading will either be too short or too long because the clock rate in the distance formula will be other than the predetermined rate. The speed reading however will be exactly right no matter what the clock rate is.
Work that out and you will know how the device works and why the absolute distance is not used in the speed calculation.
Crack on with that and I will drop by in a month or two to see if there is any expertise in speed guns on here but me.
Pip-pip
Here's a point for you to ponder.The distance accuracy is dependent upon the rate at which the internal clock oscillates. If it is exactly as designed the distance and speed will read correctly.
If the internal clock slows of speeds up or varies from the designed rate the distance reading will either be too short or too long because the clock rate in the distance formula will be other than the predetermined rate. The speed reading however will be exactly right no matter what the clock rate is.
Work that out and you will know how the device works and why the absolute distance is not used in the speed calculation.
Crack on with that and I will drop by in a month or two to see if there is any expertise in speed guns on here but me.
Pip-pip
Edited by tapereel on Tuesday 24th November 17:32
You're talking absolute b
ks!Davo93 said:
HantsRat said:
Congrats!
Do let us know full details. Interested to know what the error was.
Very QuicklyDo let us know full details. Interested to know what the error was.
1. The speed not being written on the ticket
2. No offence, but two absolutely useless Police Officers who clearly had little court experience, ably assisted by an equally useless CPS rep.
Pete317 said:
tapereel said:
OK boys and girls, here's a puzzle for you all to ponder.
The distance accuracy is dependent upon the rate at which the internal clock oscillates. If it is exactly as designed the distance and speed will read correctly.
If the internal clock slows of speeds up or varies from the designed rate the distance reading will either be too short or too long because the clock rate in the distance formula will be other than the predetermined rate. The speed reading however will be exactly right no matter what the clock rate is.
Work that out and you will know how the device works and why the absolute distance is not used in the speed calculation.
Crack on with that and I will drop by in a month or two to see if there is any expertise in speed guns on here but me.
Pip-pip
Here's a point for you to ponder.The distance accuracy is dependent upon the rate at which the internal clock oscillates. If it is exactly as designed the distance and speed will read correctly.
If the internal clock slows of speeds up or varies from the designed rate the distance reading will either be too short or too long because the clock rate in the distance formula will be other than the predetermined rate. The speed reading however will be exactly right no matter what the clock rate is.
Work that out and you will know how the device works and why the absolute distance is not used in the speed calculation.
Crack on with that and I will drop by in a month or two to see if there is any expertise in speed guns on here but me.
Pip-pip
Edited by tapereel on Tuesday 24th November 17:32
You're talking absolute b
ks!V8LM said:
I was pointing out that speed can be measured without explicitly measuring distance. The LTI measures speed by recording the time for a number (60 for some devices) of 4 ns light pulses to be returned. Speed towards the device is calculated as the rate at which these echo-times decrease. 75% of the echoes have to be valid (i.e. their return time has to be within 1.3 ns of when it should have been for the calculated speed) in order for the device to give a reading.
Yes, it works by measuring the rate of change in propagation time, iow the change in distance.The 905nm wavelength of the light used is several orders of magnitude too short to be of any practical use as a Doppler measurement device - something far more suited to centimetre-wavelength radar.
Edited by Pete317 on Tuesday 24th November 17:58
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