pulse induction. PPS, Hz and Interference

[kt315]

Eric Foster spirit stand up and bringing to light again.
repeat the matters here, for hard fixing.

PPS

PULSE FREQUENCY or PULSE REPETITION RATE. The number of times the transmitter pulse* is repeated every second. The frequency affects the response speed, power consumption and interference rejection, although all of these are influenced by many other factors in the circuit design. Examples are:- Surfmaster 800 pulses per second (p.p.s.)* Deepstar 3000 p.p.s. Aquapulse 170 p.p.s. Superscan 66 p.p.s.

transmitter pulse - we say yet TX PULSE
PPS - pulses per second

[kt315]

---------------interference----
Hi John,
Here is a copy of a post I made a couple of years ago which deals with this subject.
RELEVANCE OF PULSEFREQUENCY in a P.I. DETECTOR.
A question that is often asked about P.I. detectors is the relevance of the pulse frequency. Some detectors run at a hundred or so pulses per second while others run at several thousand. The first archaeological detectors I worked on ran at 22 p.p.s. Inlater versions we upped it to 43, then 170. The important thing was to avoid the same frequency as power lines, 50Hz in the UK, 60Hz in the US. Multiplesof the power frequencies also had to be avoided e.g. 100 or 120. Severe beatnote interference would result if the detector and power frequencies coincided;that is if you were anywhere near power lines as is often the case in the UK.
P.I. detectors running at low frequencies usually pulsed high currents through the coil, 5 - 10 amps being a typical figure. The on / off time ratio of the pulses was high so theaverage current drawn from the battery would be 100 - 200 milliamps.
Many of todays detectors favour much higher pulse frequencies. This puts the detector well away from power line interference but low frequency radio transmitters can then start to cause problems. Faster pulse rates also have the advantage in that the responseof the detector can be made more rapid, which aids in pinpointing an object.Fast pulse rates require that the pulse current be less, otherwise things wouldstart to run hot and the battery life would be rated in minutes. The pulsecurrent can be restricted by a lower transmitter voltage but more usually by aresistor in series with the coil or by making the coil more resistive by usingfiner wire. 0.1 - 1 amp pulse currents being typical. One major factor indetermining pulse current is acceptable battery life. With rechargeables 5 - 10hours is OK, while standard alkaline cells would be expected to give 15 - 25hours for the cost to be acceptable. One or two recent detectors on the market appear to have energy recovery circuits which make the transmitter more efficient and significantly increase battery life.
The pulse frequency has little effect on detector performance; one running at 170 p.p.s. could have thesame range as one running at 5000 p.p.s. but there are many inter-related factors that determine the final performance, not least the design of the receiver circuit.
Hope this helps. Ifavour higher pulse rates (1500 - 5000) in my current designs.
Eric.

[kt315]

Posted by: bbsailor(---.proxy.aol.com)
Date: March 12, 200509:37PM


Chris,
With PI pulsed wave forms that typically have much less than 50% on duty cycles, the term PPS (pulses persecond) is a more accurate way to describe the pulse speed than using the term KHz. I have seen the pulse speed refered to both ways but the term PPS clearly refers to PI machine pulses as distinctly different from VLF machines that workin the low KHz range.
I'm sure there are other better explainations.
bbsailor

[kt315]

==========================PPS
Re: PI comparisons


Posted by: AllanWestersten (---.dsl.scrm01.pacbell.net)
Date: March 13, 200501:51AM


A little more technicalexplanation:
The term "Hz" refers to cycles per second. In the case of sine-wave excitation of the transmitter coil,
a cycle consists of apositive-going half-cycle followed by a negative-going half-cycle.
In similar fashion, a PI cycle usually consists of a positive pulse, followed by a negative pulse.
A 10 kHz operating frequency therefore corresponds to 20,000 pps.
A synchronous demodulator inverts the polarity of every other signal sample received, thus adding the target signal samples. In contrast, asynchronous signals, such as might be induced in the receiver coil by magnetized rocks ("lodestones"), are cancelled, along with DC offsets in the amplifiers.
I hope this helps...

[kt315]

The standard voltage and frequency of alternating current (AC) electricity used in homes varies from country to country throughout the world. Typically, either 120-volt AC or 240-volt AC is used. Also, most countries use 50Hz (50 Hertz or 50 cycles per second) as the AC frequency. Only a handful use 60Hz.
The standard in the United States is 120V and 60Hz AC electricity. However, due to fluctuations, the average measured voltage is 117 VAC.

(For a listing in various countries, see List of Worldwide AC Voltages and Frequencies.)

There is controversy over which frequency system is better. Also, the movement in many countries is toward using higher voltages.
You need to check your equipment specifications when using electrical devices in a country with a different voltage and frequency system than yours.
Questions you may have include:

• How were the voltage and frequency values selected?
• How do the values compare?
• What happens when you visit another country?

This lesson will answer those questions. Useful tool: Units Conversion

[kt315]

How values were selected

The type of electricity delivered to homes and businesses was initially direct current (DC) but then changed to alternating current (AC) electricity. AC frequencies varied considerably, according to equipment used. For example, electrical generators at Niagara Falls put out 25Hz power.
Tesla starts AC

Early in the history of electricity, Thomas Edison's General Electric Company was distributing DC electricity at 110 volts in the United States.
Then Nikola Tesla devised a system of three phase AC electricity at 240 volts. Three-phase meant that three alternating currents 120° out of phase were combined in order to even out the great variations in voltage occurring in AC electricity. He had calculated that 60 cycles per second or 60Hz was the most effective frequency. Tesla later compromised to reduce the voltage to 120 volts for safety reasons.

(See the biography of Nikola Tesla for more information.)

With the backing of the Westinghouse Company, Tesla's AC system became the standard in the United States. Westinghouse chose 60 Hz because the arc light carbons that were popular at that time worked better at 60 Hz than at 50 Hz.
Europe goes to 50Hz and 230V

Meanwhile, the German company AEG started generating electricity and became a virtual monopoly in Europe. They decided to use 50Hz instead of 60Hz to better fit their metric standards, but they stayed with 120V.
Europe stayed at 120V AC until the 1950s, just after World War II. They then switched over to 230V for better efficiency in electrical transmission.
U.S. stays at 120V, 60Hz

The United States also considered converting to 220V for home use but felt it would be too costly, due to all the 120V electrical appliances people had. A compromise was made in the U.S. in that 240V would come into the house where it would be split to 120V to power most appliances. Certain household appliances such as the electric stove and electric clothes dryer would be powered at 240V.
Exceptions

For various reasons, Brazil and Japan have multiple standards.
Brazil

In Brazil, most states use between 110V and 127V AC electricity. But many hotels use 220V. In the capital Brasilia and in the northeast of the country, they mainly use 220-240V. All operate at 60 Hz.
Japan

In Japan, they use the same voltage everywhere, but the frequency differs from region to region.
Eastern Japan, which includes Tokyo, uses 50Hz. In 1895, Japan purchased 50 Hz electrical generators for Tokyo from the German company AEG. This was the same as what was done in Europe. In 1896, the American company General Electric provided 60Hz generators to cities in western Japan, which includes Osaka and Kyoto.
It is unfortunate that they did not coordinate their efforts. Having different voltages and frequencies within the country not only must be confusing for the people but also can result in extra costs for appliances and adapters.

[kt315]

1 Hertz

[kt315]

[ionut_mtb]

==========================PPS
Re: PI comparisons


Posted by: AllanWestersten (---.dsl.scrm01.pacbell.net)
Date: March 13, 200501:51AM


A little more technicalexplanation:
The term "Hz" refers to cycles per second. In the case of sine-wave excitation of the transmitter coil,
a cycle consists of apositive-going half-cycle followed by a negative-going half-cycle.
In similar fashion, a PI cycle usually consists of a positive pulse, followed by a negative pulse.
A 10 kHz operating frequency therefore corresponds to 20,000 pps.
A synchronous demodulator inverts the polarity of every other signal sample received, thus adding the target signal samples. In contrast, asynchronous signals, such as might be induced in the receiver coil by magnetized rocks ("lodestones"), are cancelled, along with DC offsets in the amplifiers.
I hope this helps...

This is good thread KT, thank you for it.

I do not understand the highlighted afirmation 10khz=>20000pps

10000hz=1/f => f=0.0001s=100us => 10000pps

[kt315]

afirmation has been gave by members and by Eric Foster long time ago in PI TECHNOLOGY FORUM (now its only Tech forum)
http://www.findmall.com/list.php?34

=========================PPS===
Posted by: bbsailor (---.proxy.aol.com)
Date: March 12, 2005 09:37PM


Chris,
With PI pulsed waveforms that typically have much less than 50% on duty cycles, the term PPS (pulses per second) is a more accurate way to describe the pulse speed than using the term KHz. I have seen the pulse speed refered to both ways but the term PPS clearly refers to PI machine pulses as distinctly different from VLF machines that work in the low KHz range.
I'm sure there are other better explainations.
bbsailor
==========================PPS
Re: PI comparisons


Posted by: Allan Westersten (---.dsl.scrm01.pacbell.net)
Date: March 13, 2005 01:51AM


A little more technical explanation:
The term "Hz" refers to cycles per second. In the case of sine-wave excitation of the transmitter coil,
a cycle consists of a positive-going half-cycle followed by a negative-going half-cycle.
In similar fashion, a PI cycle usually consists of a positive pulse, followed by a negative pulse.
A 10 kHz operating frequency therefore corresponds to 20,000 pps.
A synchronous demodulator inverts the polarity of every other signal sample received, thus adding the target signal samples. In contrast, asynchronous signals, such as might be induced in the receiver coil by magnetized rocks ("lode stones"), are cancelled, along with DC offsets in the amplifiers.
I hope this helps...

[dbanner]

Any electromagnetically radiated signal which is repetitive in the time domain must have a frequency of repetition. The unit for frequency is HERTZ. Pulses per second(pps) as it relates to P.I machines only infers a frequency, but that's because engineers are using Pulse induction jargon among themselves. A commercial P.I detector must have a published operating frequency in order to be in compliance with rules and regulations governing the frequency spectrum. Otherwise simply describing a P.I detector as simply having 1000 PPS for example, would not be sufficient. In which bandwidth? You could have 300Mhz signal pulsing at 1000 PPS, for example. See what I mean?

[kt315]

author=Super Pierrot -- Hello everybody. As I said while presenting myselft, I am french and I made a Delta Pulse thanks to all informations shared by a few specialized members. I would like to ask a few questions and participate with my experience about this PI detector. I am prospecting near huge power lines with a big frame and I am forced to reduce very much the power of the detector to avoid shattering. I understand calibrating frequency of the detector on the power lines fequency (50HZ in France) help reducing this shattering. Is it true or should I avoid a multiple frequency (100hz 150hz etc...)?

....

[TANCE]

XR-71如何改善

[kt315]

with YOUR english are you able to grasp what he tells?

https://www.liveleak.com/view?t=aERDQ_1564166694

[Andi68]

Thenk you!