Noise on FRP Sensor Captures & Noise in General

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Noise on FRP Sensor Captures & Noise in General

Postby STC » Wed Feb 08, 2017 10:26 pm

I have a 4 Channel 3000 Series so possibly not the best equipped / qualified to raise this issue.

In the last week we have had 2 Colleagues side tracked from the real issue by Noisy FRP Waveforms:

RS 4 with the Volvo V50 topic16201.html
and
Victor with the BKC Golf - topic16191.html (outcome still pending)

There have been other noise issues in the past threads where that "noise" has manifested to be just that - "Noise" - Not part of the problem.

The common denominator, always, is that they have a 4000 Series Pico. Others have made observations, comparisons and comments on this in a previous threads.

My deduction is that the 4000 series is that it can see and display more of the noise that is actually there under the bonnet. Perhaps the "Filter Function" is there for that reason.

Just a "Keep it Simple" observation.
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Re: Noise on FRP Sensor Captures & Noise in General

Postby FioranoCars » Wed Feb 15, 2017 10:04 pm

Sadly we've had noise issues on both 3000 and the latest 4000 Automotive scopes, while sometimes we're been able to identify causes ... here's the top 4!
1. Noisy PSU for Laptop (run from battery or alternative PSU reduces/remove the issue)
2. Car battery being charged (some trickle chargers especially bad for this, others give no issue)
3. Routing of cables
4. Poor USB connection (try different port or alternative cable)

BUT other times we've been unable to determine the source, swapping scopes sometimes has some effect but can't see why, as it's not swapping the 3000 for the 4000, it's random reversal (could be USB connections/pins - but not always).

At the moment we have a car with a parasitic drain, while it sits at a base of circa 30-50ma, it jumps to over 200ma every 3 seconds for a short spike. I thought I'd use this example, which on a DMM using an AMP clamp fails to show the issue, to demonstrate volt drop across a 0.01 ohm resistor (the example STC pointed out on Ebay a Gold heatsinked 5% 100W ~ good for about 7amps max) and a 50Amp J Case fuse (resistance of 0.00099 ohms) and a 7.5amp Mini fuse (0.01085 ohms - so close the Gold 100W Resistor but hopefully a closer tollerance! or not ... yet to be proven).

However right now on 2 separate days, we have had better results using the Pico 30amp Clamp (see the main Pico site, it's not in the Automotive range) than any of these, due to noise, filtered or not, it's making the volt drop measurements useless. We've reduced the sample rates, tried active filters and up to 16bit resolution enhancement ... nothing helps much. For the volt drop we're using the 4000 for it's floating capability. Could try using the 3000 series but we'd need to drop 1 channel to do that, not ideal.

Anyone had success in Voltdrop amp measurement as outlined above?

Thanks
Richard

PS ... STC ... any news on the airbag ECU? :D
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Re: Noise on FRP Sensor Captures & Noise in General

Postby STC » Thu Feb 16, 2017 4:17 am

At the moment we have a car with a parasitic drain, while it sits at a base of circa 30-50ma, it jumps to over 200ma every 3 seconds for a short spike


Possibly Alarm Siren or Tracker (with internal rechargeable battery) Seen a few F360's with that - Removing the Hazard /Indicator fuse will prove it :D :D :D (Spoiler Alert) :D :D :D

Anyone had success in Volt drop amp measurement as outlined above?


I have had success using the Resistor, Works and compares well to having a DMM in Series. Not tried the J Case Fuse yet.

I have yet to come across (excessive) Noise that I have not overcome with:
1. Noisy PSU for Laptop (run from battery or alternative PSU reduces/remove the issue)
2. Car battery being charged (some trickle chargers especially bad for this, others give no issue)
3. Routing of cables


Perhaps I should get out more :)

Here is a weird one, you would not believe it if you did not see it with your own eyes. Cant tell you if it would contribute to noise on a scope but here goes:

I have a customer local to me, They run a Motor Factors on a main road location, Behind the Shop, across a 20 foot alley way is a 3 bay workshop. Both the Shop and Workshop have every thing electric running efficiently - Light, Heat, Wireless Internet, Phone Chargers, Alarm, RF Remote Shutters .... ..... ..... all the Mod Cons, the whole lot.

I have a standard Samsung S7 with genuine Mains Charger and USB Lead - In the Shop I can charge it from the USB on his PC but NEVER from the Mains - Not in one of about 20 sockets !!!

In the workshop I can charge it in any one of the sockets. Can it be the building ???
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Re: Noise on FRP Sensor Captures & Noise in General

Postby FioranoCars » Thu Feb 16, 2017 10:45 am

STC wrote:
Samsung S7 with genuine Mains Charger and USB Lead - In the Shop I can charge it from the USB on his PC but NEVER from the Mains




Would be worth checking the mains polarity, would not be the first building where a clever sole confused live and neutral ... And yes most stuff surprisingly works despite this. Dmm can check this simply, or a plug in socket tester .... but also your dmm will show you hertz and voltage of the supply, lots of properties suffer low input supply plus the dmm can show you the USB tip voltage, is it 0 or actually 5v.

Compare mains readings to the workshop, very much doubt a cable connected charger would be environment affected for charging, if the input is good, the output will be, something is going to be out of spec. 3 phase rotation, and using different phase should be no impact, as most building will be wired with different phases to balance load, you'd need to access the distribution board to check that, as it might be only 1 phase that has the problem.... I'm sure others out there especially on the main pico forum will have far more to offer you than my basic musings...

The charger could be borderline, and the supply just out of spec enough to make it fall over, while the PC PSU is more forgiving and able to step down to a good internal 5v without any issues.

Of course it might be that when you unplug my airbag ecu the building supply surges up a few volts in relief and everything works again! :D

On the parasitic, yes alarm and trackers are top of the suspect pool, it's a yank model and trying to find the aftermarket bits as non factory ...

Will put the resistor setup and other methods into a dmm and second scope to compare things, but the noise is becoming a pain we could do without, or at least some solid ideas of how to avoid /minimise it.

Richard
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Re: Noise on FRP Sensor Captures & Noise in General

Postby STC » Thu Feb 16, 2017 10:14 pm

Of course it might be that when you unplug my airbag ecu the building supply surges up a few volts in relief and everything works again! :D


I cant imagine the surge when I bring it back and the light goes out !!!
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Re: Noise on FRP Sensor Captures & Noise in General

Postby andrewbishop66 » Fri Feb 17, 2017 12:26 am

Hi All

in regards
Anyone had success in Volt Drop amp measurement as outlined above?


my favorite method is a 75amp shunt in parallel with a battery isolator switch with a male neg terminal on one end and a female terminal on the other switch closed the shunt is bypassed you can start the vehicle open the switch and you can see the voltage drop across the shunt to measure amps you can also see the charge rate going into a depleted battery
IMG_2451 (1).JPG


incidentally the small box attached is a voltage amps and watt meter the idea was to have a running total of total power used by the circuits on the car but unfortunately the meter lost resolution under about 2 amps current draw but the voltage is accurate so it has its use

Shunts are normally calibrated by reducing the width (saw cut )

As Always just my musings

Thanks Andrew
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Re: Noise on FRP Sensor Captures & Noise in General

Postby FioranoCars » Fri Feb 17, 2017 5:08 am

STC rofl !!!!!! :D the only surge will be smiles. BY the Bucket load!

Andrew, a man after my own heart ... A plan and a custom tool ... Hats off to you, that's what I would do ... Except I know a 2k pico amp clamp will (OK, with slight issues) capture the crank but for para drain cranking is not part of the critical domain, maybe in my school of thought door locks are, and granted at maybe >30amps it'll blow most even 20amp dmm fuses, there are plenty of simple no-break-the-circuit work arounds.

I've looked at a few other devices to.neasure current but the need to record verse time the results brings a dead ends to many possibles solutions... I'm very disappointedly stil using amp clamps, kicking and screaming, but nothing yet robust enough to replace the wandering temperature sensitive battery killing things...

Sadly this para drain cars gone without time authorised to trace the fault, so till next time, this attempt to compare methods is on hold.
Richard
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Re: Noise on FRP Sensor Captures & Noise in General

Postby STC » Sat Feb 18, 2017 10:49 pm

Sadly this para drain cars gone without time authorised to trace the fault, so till next time, this attempt to compare methods is on hold.


Richard

Why not build a training rig with a 50 mA draw. Then fit "Secret" switches that add additional parasitic drains, may be timers, bulbs etc.

That way you could compare all the test methods ?
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