Coil-On-Plug Ignition Probe and 600A clamp

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Coil-On-Plug Ignition Probe and 600A clamp

Postby silverdollar » Fri May 04, 2012 10:59 am

Hi,
Does the Coil-On-Plug Ignition Probe and 600A clamp work on any oscilloscope other than pico?

thanks Regards,
Paul
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Re: Coil-On-Plug Ignition Probe and 600A clamp

Postby antthecat » Fri May 04, 2012 8:34 pm

I can't see why not, as long as you have a bnc to banana jack or adaptor to suit.
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Re: Coil-On-Plug Ignition Probe and 600A clamp

Postby Robski » Fri May 04, 2012 8:55 pm

silverdollar wrote:Hi,
Does the Coil-On-Plug Ignition Probe and 600A clamp work on any oscilloscope other than pico?

thanks Regards,
Paul


You would have to know the scales at which they work esp the amps clamp for a correct reading/scaling.
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Re: Coil-On-Plug Ignition Probe and 600A clamp

Postby silverdollar » Fri May 04, 2012 9:17 pm

About the clamp the scaling is [Voltage output 1 mV per 1 A (0 to 600 mV AC & DC)] so it wouldn't be any difficult to calculate it. I'm concerned mainly about the coil on plug probe although on the website it says [Works on all labscopes capable of displaying ignition patterns] although I'm not sure about the voltage scaling for that one. Since the voltage induced from the probe is scaled via the picoscope software?
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Re: Coil-On-Plug Ignition Probe and 600A clamp

Postby Alan » Wed May 09, 2012 7:16 pm

Hi,

The COP probe should be OK with most other scopes provided the scope is fast enough, has enough memory, voltage ranges (to cope with well screened coils) etc. To be honest its probably easier if you post what scope you are planning on using and we can check the specs. (You may have to put up with some abuse for choosing the wrong scope in the first place though :D )
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Re: Coil-On-Plug Ignition Probe and 600A clamp

Postby silverdollar » Wed May 09, 2012 9:40 pm

Hi, my scope that I have atm is pc based 4ch 60Mhz, 200 MSa/s, 1 MΩ / 25 pf Capacitance, 400V max input, 10K-16M/Ch memory depth. I think that it should work, not interested that much in the voltage reading in KV as such. As long as the secondary ignition waveform is visible clear enough to diagnose the problem if any I'm happy
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Re: Coil-On-Plug Ignition Probe and 600A clamp

Postby Alan » Thu May 10, 2012 12:49 pm

Hi, I recognize the specifications of that scope. Our Chinese friends seem to have "borrowed" the specifications (and more besides) from a now obsolete scope we manufacture for the electronics market. Still as the saying goes imitation is the sincerest form of flattery.

The input ranges should be OK for both the current clamp and COP probe but the main issue will be that your scope is not really an automotive scope. It only has 8 bit resolution so when measuring a signal that goes from 0V to say 2V you will only have 128 vertical steps. If the signal is say from 0 to 2.1V then you only end up with about 50 vertical steps as you need to use the 5V range, at this point you start to really struggle with waveforms like ignition.

Here is an ignition waveform at 12 bits:

12bit.png


Here is one at 8 bits:

8bit.png


The situation with the current clamp should be better, the main problem here (apart from resolution) is that you will not be able to filter out any noise as there is no programmable low pass filter. I think you have a fixed 20MHz filter, but again thats more use in electronics than automotive.

In short they will work OK ish and with a bit of care will be fine for diagnosing faults.
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Re: Coil-On-Plug Ignition Probe and 600A clamp

Postby silverdollar » Thu May 10, 2012 6:12 pm

True, the vertical resolution plays a very important part. its like having a monitor with a res of 1920x200. However in the case of the pictures that you attached, can't you choose a small suitable scale V/div and view only that part of the waveform which wasn't resolved correctly. (sort of to zoom in that area). Wouldn't that part of the waveform zoomed in be pictured with better resolution then before? since you have a smaller V/div and the 8bit res is only applied to that part? So that area of small voltage fluctuations would be resolved better? Don't know if I'm speaking wrong I'm quite new with this.
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Re: Coil-On-Plug Ignition Probe and 600A clamp

Postby Alan » Thu May 10, 2012 6:57 pm

Hi,

With a 8 bit scope you have 256 vertical levels or steps (With a 12 bit scope its 4096 which is typically more than the resolution of your display - a HD scope if you like.).

The 256 (4096 for 12 bit) levels are spread out across the voltage range. Many automotive signals are unipolar (eg 0 to 5V for many sensors) so as the scope input range goes from -5V to +5V you only have 128 steps (2048 for 12 bit) for the 0 to 5V sensor input. The problem gets worse if your input signal does not match the input range of the scope. For example to measure a 24V signal you will need to use a 50V range so over the 0 to 24V range you only have 61 (983 for 12 bit) vertical steps which looks pretty awful.

For the ignition waveform you could try to use a too small a voltage range so that the peak kV signal goes off the top of the screen. This may give you a better view of the firing line / coil oscillations etc but the problem is that you are overloading the input channel with an out of range signal. This should not damage the scope provided the input is below the max rated input of the scope but it may distort the waveform so make diagnosis difficult. The opposite is true with a 12 bit scope - you can be fairly lazy with the range selection and then just zoom in on the area of interest.

You might wonder why most electronics scopes are 8 bits when you have the issues above - the simple reason is that fast 8 bit ADC converters are much cheaper than equivalent higher resolution ones. Our scopes offer resolution enhancement and waveform averaging which can reduce the effects above for some signals - not sure if your scope has these options or not.

Dont get too worried about this, you can still learn plenty / diagnose most situations with an 8 bit scope. I just wish companies would not advertise products as automotive scopes when they are not.
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Re: Coil-On-Plug Ignition Probe and 600A clamp

Postby silverdollar » Thu May 10, 2012 7:35 pm

Thanks for the helpful explanation I appreciate. Sad that most companies only highlight the bandwidth and sample rate
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