Chronograph Electrical Interference

[Barry Davies]

Off that particular subject -- Question for Geoff or Rod

I do a great deal of chronographing and notice that quite regularly the chrono will for no apparent reason register "error " As it does this when the hand held radio is operated I assume it is something to do with radio interference. It is most notable at Bendigo which is adjacent to the airport.
Obviously it is radio interference and the question is could something like this happen to electronic targets thus giving false readings?

Barry

[ger]

Off that particular subject -- Question for Geoff or Rod

I do a great deal of chronographing and notice that quite regularly the chrono will for no apparent reason register "error " As it does this when the hand held radio is operated I assume it is something to do with radio interference. It is most notable at Bendigo which is adjacent to the airport.
Obviously it is radio interference and the question is could something like this happen to electronic targets thus giving false readings?

Barry

A transmitter in close proximity could, I suppose, cause a problem. But a hand-held is not very powerful.

I would be inclined to look at whether or not there are some high-current electrical devices nearby - such as power supply utility transformers - that might be inducing low frequency (50Hz) energy into un-shielded conductors (wires).

I don't know what sort of immunity measures the chronograph has employed against RFI or EMI. As with reducing emissions, appropriate shielding of electronics and cables (amongst other methods) can improve immunity if there is a problem.

Geoff.

[Triplejim]

I do a great deal of chronographing and notice that quite regularly the chrono will for no apparent reason register "error " As it does this when the hand held radio is operated I assume it is something to do with radio interference. It is most notable at Bendigo which is adjacent to the airport.
Obviously it is radio interference and the question is could something like this happen to electronic targets thus giving false readings?
Barry

We discovered last year it's the electrical substation at 1000 yards, ok at other end of mound and 900 forward. James

[Barry Davies]

Hi James,
This was at 300 yards so it's not the 1000yd sub.
Barry

[Triplejim]

Hi James, This was at 300 yards so it's not the 1000yd sub. Barry

Only trouble I had at 300 was fellow shooter planting shot into skyscreen~!

[dmitri]

Off that particular subject -- Question for Geoff or Rod

I do a great deal of chronographing and notice that quite regularly the chrono will for no apparent reason register "error " As it does this when the hand held radio is operated I assume it is something to do with radio interference. It is most notable at Bendigo which is adjacent to the airport.
Obviously it is radio interference and the question is could something like this happen to electronic targets thus giving false readings?

Barry

The question was addressed to Rod or Geoff, as you raised it in the forum, I assume you wouldn’t mind if I add my comment to the answer :

I 100% agree with ger that the electrical wires nearby may cause the problem.
However I disagree with the statements about low power of handheld radio transmitter.
Hand-held radios and mobile phones have the transmitting power of 1-5 Watts, which is very high power in respect to sensors used in devices. This is the reason why radio transmitting devices are strictly prohibited on airplanes and in hospitals, they may affect the sensitive measurement devices.

Two examples from my personal experience. It would show how powerful hand-held transmitters are:
Once during the experiment I managed to permanently destroy a digital(!!!) control module by switching the handheld radio to transmitting mode within 30cm distance from the device.
Second: during a validation of one of the sensor circuitry in a medical device in the lab the results were so odd, that we had to search for external interference and found that the person used his mobile phone about 25 meters away was causing the interference.

The EMI (ElectroMagnetic Immunity) is an art in electronic design. The EMI testing is part of CE certification process but, unfortunately not C-Tick certification in Australia. However it is a good engineering practice to consider FR interference during the design and measurement. As the EMI performance of your device is unknown in addition to what Ger already said I would recommend:

1. when you've taken the measurements make sure that hand-held transmitter is not closer than 20 meters to you or not in the transmitting mode .
2. you have no switched ON mobile phone devices closer than 10 meters.
3. you conducting the number of tests for the same setup and during these tests you receiving the constant results. Unknown (non-characterized) errors are unacceptable in measurement. Find the source of errors and analyse how it may affect your results. The RF may also induce the unnoticeable error to your measurement. In System Engineering an unnoticeable error is considered as more serious error than the error, which is detected/reported by system or user.

Dmitri

[Triplejim]

However I disagree with the statements about low power of handheld radio transmitter. Dmitri

We had an issue at Bendigo when I loaned my chronigraph to Aust Vets,
they started well but RO came over to look at procedings and errors started.
Later they realised the radio was the cause.

We had same issue at Wangaratta but I ask everyone to turn off mobile phones and radio is at back of mound.
You can guarantee anyone that comes to the mound with a mobile switched on
it will cause the chroni to spit out rows of zero velocity, James

[Barry Davies]

Geoff, Dmitri

Thanks for taking the time to reply to my query re radio interference to the chronograph, however the question still begs an answer.
In my case I know that the handheld radio does cause problems but at Bendigo I am 700 yards from the transformer and further from the airport but something is causing the interference ( not mobile phone )

Could this electrical interferrence from an unknown source disrupt the workings of electronic targets thereby giving false results? -- if so, is any shielding employed guaranteed to prevent such a thing happening from all sources.

Thanks,
barry

[dmitri]

Geoff, Dmitri

Thanks for taking the time to reply to my query re radio interference to the chronograph, however the question still begs an answer.
In my case I know that the handheld radio does cause problems but at Bendigo I am 700 yards from the transformer and further from the airport but something is causing the interference ( not mobile phone )

I had an experience when a radar 4 km away, at an airport, caused interference with almost all the equipment for a fraction of a second and with ~10 second period (actually you can see when the radar turns to our direction and hear the "ringing" interference signal in the audio equipment at the same time).

Regarding the chronograph error: The chronograph which I had an experience with, used light to detect when the projectile approaches 3 frames. Because it uses light I suspect it may be sensitive to the sunlight. Also it is possible that the measurement error may vary with the background light intensity. Try to introduce some shade above the unit and see if it would reduce the frequency of error results.
Honestly I did not like the design of chronograph I saw it uses the flimsy frames as the part of the sensors, which may potentially move with the muzzle blast or wind and it may affect the accuracy. I would not rely on this device for the accuracy better than 10% of reading. I may be wrong as I did not do any testing and have very limited experience to play with this this device. (Our club member brought me it for repair) Also maybe your device has different design and uses another method to measure the speed of the projectile.

Could this electrical interferrence from an unknown source disrupt the workings of electronic targets thereby giving false results? -- if so, is any shielding employed guaranteed to prevent such a thing happening from all sources.

Thanks,
barry

Yes. We spent a lot of effort to to design EMI compliant product and introduced the number of special engineering solution to improve EMI performance, especially as we were aware that the Butts officer may use the radio nearby the system. See Product Description section, paragraph 6

We conducted the EMI tests, one of them were we switched a 5Watt handheld transmitter with antenna 5cm away from the most sensitive part of the system - target sensors (the same as I managed to destroy the one Motor controller). We received no faulty reading from the sensors affected by RF radiation. It did not affected the system in any way.

The shielding is one of many methods to improve EMI performance. Incorrectly implemented shield may introduce more problems than w/o shield at all

[Barry Davies]

Question answered, thanks Dimitri.
The problems you mention with the chronograph I am well aware of and take the necessary steps to eliminate but the airborne electrical interference is still there -- just a matter of telling the chronograph to ignore it.

Barry