LTI 20-20 UltraLyte 100 Calibration checks

[Pete317]

tapereel said:

Oh really! Why?

Why? Because you've said nothing that leads me to believe that you have the slightest idea what you're talking about.

So prove me wrong!
Demonstrate that you really do know how it works.

[cptsideways]

tapereel said:

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

Edited by tapereel on Tuesday 24th November 17:32

Here's a point for you to ponder.

You're talking absolute bks!

Oh really! Why?

Your suggesting the distance clock rate is monitored by the algorithm that does the calcs then, or it takes or looks for multiple readings over the range of the clock variance. AKA a fudge factor or inaccuracy tolerance

[V8LM]

Pete317 said:

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.

[Monty Python]

Here's how it works:

http://www.google.co.uk/patents/US5359404

[Pete317]

Monty Python said:

Here's how it works:

http://www.google.co.uk/patents/US5359404

Yes, now show this to tapereel.

Especially this bit:

"The laser rangefinder, under the supervision of the controller, fires a series of laser pulses at a selected remote target at known time intervals, and detects reflected laser light from each pulse. Preferably, the pulses are fired at equally-spaced intervals. The laser rangefinder further determines count data reflective of the time-of-flight of each pulse to the target and back, and provides these data to the control means. These count data comprise the respective arrival times of a REF (reference) pulse representing the firing time of the laser pulse, and an RX pulse representing reflected laser pulse light."

"The microcontroller is configured to read these count values and to compute from them, the time-of-flight of the laser pulse and in turn, the distance to the target. The controller then computes the velocity of the target relative to the speed detector from the change in distance to the target divided by the known elapsed time between firing of the pulses."

[V8LM]

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

Edited by tapereel on Tuesday 24th November 17:32

You can't practically measure something that is a function of time if you have no measurement of time, either assumed or referenced.

ETA: 'practically'.

Edited by V8LM on Tuesday 24th November 21:19

[tapereel]

Pete317 said:

Monty Python said:

Here's how it works:

http://www.google.co.uk/patents/US5359404

Yes, now show this to tapereel.

Especially this bit:

"The laser rangefinder, under the supervision of the controller, fires a series of laser pulses at a selected remote target at known time intervals, and detects reflected laser light from each pulse. Preferably, the pulses are fired at equally-spaced intervals. The laser rangefinder further determines count data reflective of the time-of-flight of each pulse to the target and back, and provides these data to the control means. These count data comprise the respective arrival times of a REF (reference) pulse representing the firing time of the laser pulse, and an RX pulse representing reflected laser pulse light."

"The microcontroller is configured to read these count values and to compute from them, the time-of-flight of the laser pulse and in turn, the distance to the target. The controller then computes the velocity of the target relative to the speed detector from the change in distance to the target divided by the known elapsed time between firing of the pulses."

Keep going.

[tapereel]

V8LM 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

Edited by tapereel on Tuesday 24th November 17:32

You can't practically measure something that is a function of time if you have no measurement of time, either assumed or referenced.

ETA: 'practically'.

Edited by V8LM on Tuesday 24th November 21:19

Keep going.

[Rovinghawk]

tapereel said:

Not writing the speed down is the first error but even then it wasn't necessary with two witnesses to the event.

Based on the not guilty verdict, I reckon you're wrong.

[V8LM]

tapereel said:

V8LM 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

Edited by tapereel on Tuesday 24th November 17:32

You can't practically measure something that is a function of time if you have no measurement of time, either assumed or referenced.

ETA: 'practically'.

Edited by V8LM on Tuesday 24th November 21:19

Keep going.

"First, a crystal clock-based timing analysis circuit includes a gating circuit which is a digital logic, edge-sensitive gate for which both the "opening" and the "closing" of the time window can be selectable set by the microcontroller. ... Second, the timing analysis circuitry is constructed to generate self-calibration pulses and to process them in the same manner as the REF and RX pulses, thereby producing a set of calibration interpolation counts. The controller uses these calibration interpolation counts along with the REF and RX interpolation counts to compute self-calibrated values of the respective fractional portions of the clock periods at which the REF and RX pulses arrived. ... This self-calibrating interpolation provides greatly enhanced resolution and accuracy of distance measurements based on elapsed time."

Velocity and distance based in timing of pulses, time based on a crystal clock.

Over to you.

[tapereel]

Rovinghawk said:

tapereel said:

Not writing the speed down is the first error but even then it wasn't necessary with two witnesses to the event.

Based on the not guilty verdict, I reckon you're wrong.

Oh an expert in the law and speed guns. NOT

[Pete317]

tapereel said:

Pete317 said:

Monty Python said:

Here's how it works:

http://www.google.co.uk/patents/US5359404

Yes, now show this to tapereel.

Especially this bit:

"The laser rangefinder, under the supervision of the controller, fires a series of laser pulses at a selected remote target at known time intervals, and detects reflected laser light from each pulse. Preferably, the pulses are fired at equally-spaced intervals. The laser rangefinder further determines count data reflective of the time-of-flight of each pulse to the target and back, and provides these data to the control means. These count data comprise the respective arrival times of a REF (reference) pulse representing the firing time of the laser pulse, and an RX pulse representing reflected laser pulse light."

"The microcontroller is configured to read these count values and to compute from them, the time-of-flight of the laser pulse and in turn, the distance to the target. The controller then computes the velocity of the target relative to the speed detector from the change in distance to the target divided by the known elapsed time between firing of the pulses."

Keep going.

Others have been saying all along that speed is computed from the change in distance over time, as described here, only for you to continue asserting that they're wrong and that it measures speed by some other apparently mysterious means without any reference to distance - relative or otherwise.

Then you change tack and start alluding to clock accuracy and drift - the kind of which used to be a problem in the very early days of electronics, but ceased to be a practical issue some time before you were born.

So why should anyone believe that you know what you're talking about, and that you're not just making it up as you're going along?

Edited by Pete317 on Wednesday 25th November 08:38

[cptsideways]

tapereel said:

Oh an expert in the law and speed guns. NOT

You do not have to be an expert to defend your innocence or someone elses guilt, it helps but if you can prove a valid point & its upheld it does not make one an expert.

[tapereel]

Pete317 said:

Others have been saying all along that speed is computed from the change in distance over time, as described here, only for you to continue asserting that they're wrong and that it measures speed by some other apparently mysterious means without any reference to distance - relative or otherwise.

No I haven't

Pete317 said:

Then you change tack and start alluding to clock accuracy and drift - the kind of which used to be a problem in the very early days of electronics, but ceased to be a practical issue some time before you were born.

No I didn't

Pete317 said:

So why should anyone believe that you know what you're talking about, and that you're not just making it up as you're going along?

You don't have to believe anything I say but what I will say is that all of the remarks on here about how the device works and all of the apparent interpretations of the patent text are incorrect.
Believe what you wish but I may just keep on dismissing the guff typed herein that I know to be incorrect; just so you can be aware that there is reasonable doubt about how you say these type of devices operate.

[0000]

There's nothing reasonable about saying everyone's wrong and not offering up an explanation as to why.

[Rovinghawk]

tapereel said:

Rovinghawk said:

tapereel said:

Not writing the speed down is the first error but even then it wasn't necessary with two witnesses to the event.

Based on the not guilty verdict, I reckon you're wrong.

Oh an expert in the law and speed guns. NOT

If it wasn't necessary as you claim, why the not guilty verdict?

You seem very angry. Tell us where the bad man touched you.

[tapereel]

Rovinghawk said:

tapereel said:

Rovinghawk said:

tapereel said:

Not writing the speed down is the first error but even then it wasn't necessary with two witnesses to the event.

Based on the not guilty verdict, I reckon you're wrong.

Oh an expert in the law and speed guns. NOT

If it wasn't necessary as you claim, why the not guilty verdict?

We all await that reason.

[Pete317]

tapereel said:

You don't have to believe anything I say but what I will say is that all of the remarks on here about how the device works and all of the apparent interpretations of the patent text are incorrect.
Believe what you wish but I may just keep on dismissing the guff typed herein that I know to be incorrect; just so you can be aware that there is reasonable doubt about how you say these type of devices operate.

Stop blathering.
If you know differently how the device works then why don't you tell us in your own words - bearing in mind that some of us do actually know a thing or two.

Oh, and simply asserting that someone is wrong isn't dismissing anything - you have to explain why they're wrong.

ETA: In the continued absence of any attempt at reasonable explanation on your part, you've really given no reason to conclude anything other than that you don't really know what you're talking about.

Edited by Pete317 on Wednesday 25th November 12:49

[Rovinghawk]

tapereel said:

We all await that reason.

I don't. I just accept it.

[anonymous-user]

Well done OP, I was wrong to suggest that you roll over. I gather from the brief description that, in the end, it wasn't an argument about the equipment that swung it, but poor police work by the officers in the case. Fair enough, it is incumbent on them to do their work properly.