Pulse Devil by Dave Emery

I hope that this proves of some interest to your members
Regards
Doug

THE PULSE DEVIL EXPLAINED: AN OVERVIEW

When designing a detector one is presented with a series of trade-offs. One such trade-off is the choice of how many user controls the detector will have.

Most designers have limited the number of user controls for two reasons.

The first reason is that many users don't like the idea of adjusting an instrument panel rivaling that found in the cockpit of a jet fighter.

The other reason, though less obvious, is just as important. The controls take up space. This means that the control box gets both bigger and heavier. Large control boxes and lot of controls also make the detector expensive.

To complicate things still further, the designer is faced with the fact that there are professional detector users in many parts of the world.

Some professionals seek ancient coins in Europe while others seek relics from various sites before they rot away and are lost for ever.

Still others are beating around the bush in Australia with a cold pack of tinnies on their back looking for the big one!!!

The professional user wants to get everything they can from their detector. Such a person will spend the time to learn how to adjust any number of controls available to them in order to squeeze out those extra, all important few inches of depth.

The truth is that a detector with a full complement of controls is potentially far more powerful than a detector equipped with a limited number of controls.

The challenge was to make a detector which suited everyone. A detector which could be effectively used by a either a beginner or a professional.

I decided that a make-over was in order.

The first order of business was to replace the Nickel Metal Hydride (NiMH) battery pack with a powerful Lithium Ion (Li-ion) type. The new pack is much lighter than the old one which made for a good start.

I removed all the mechanical controls and mechanical switches from the Pulse Devil and replaced them all with tiny electronic chip pots. The chip pots are adjusted by one of two on board microcomputer chips.

The removal of the mechanical controls and switches provided a control box front panel which sports only an LCD display and a single control knob.

USING THE DETECTOR

The single knob is mounted on the master control. This control knob can be turned clockwise or counterclockwise. The control knob can also be pushed in to actuate a built in momentary switch.

TURNING THE DETECTOR ON AND OFF

Pressing the knob in causes the LCD to display a message requesting that you enter a PIN number.

The numbers 0 - 9 are displayed in a row followed by the word \"ENTER\".

Turning the control knob causes each number to flash on and off in turn as the knob is rotated. As an example, the operator used the last five digits of his drivers license number for his PIN code. the PIN number is 28217.

To enter this, one simply rotates the control knob until the \"2\" flashes. Pressing the knob in will now enter the number and cause a * to be displayed on the bottom line of the display. The control knob is now rotated to where the \"8\" flashes. Pressing the knob in enters the number and causes the bottom line of the display to **.

The rest of the numbers are now entered until the bottom line displays *****

The knob is now rotated to the word \"ENTER\". The knob is pressed in and the PIN code is entered.

The detector can now be switched on and off as many times as is required for a period of 48 hours. This will render stolen Pulse Devils useless to a thief. There is, of course, a factory back door code in case anyone forgets their PIN number. The detector can be reset upon verification of ownership.

Once the detector is turned on the main menu is displayed. The menu has the following options which appear one at a time by rotating the control knob:

\"Operate\"

\"Default Settings\"

\"Manual Settings\"

\"Stored Settings\"

\"Shutdown\"

The option is selected by pressing the control knob in.

OPERATE MODE

Selecting the \"operate\" mode reloads the control settings which were in place when the detector was last switched off. You are all ready to detect.

DEFAULT SETTINGS

Selecting \"Default Settings\" provides a large number of factory preset control settings for different types of detecting such as \"Prospecting\", \"Relic Hunting\", \"Coin Hunting\", \"Beach Hunting\" and conditions such as \"Neutral Ground\" \"Mineral Ground\" \"Extreme Ground\" and \"Salt Ground\".

The default settings offer a starting point to set the detectors controls.

MANUAL SETTINGS

Selecting \"Manual Settings\" allows the user to select and change any or all of the detectors controls and settings.

Here is the list of the user accessible controls on the PD.

Threshold,

Ground Balance,

RX Gain, (similar to sensitivity)

Automatic Retune Speed,

Discrimination,

Audio Tone,

Audio Volume,

Sample Delay,

Noise Tuning (adjusts out interference by varying the operating frequency),

Display Backlight (setting can be set from OFF to full brightness in steps),

Automatic or Non Automatic Tuning Select (ON - OFF),

Transmit Pulse Width Selection:

250us

500us

750us

1000us

ON-OFF POWER SWITCHING

There is also a Battery Voltage display which displays the battery voltage with a resolution of 0.1 Volts.

STORED SETTINGS

Selecting the \"Stored Settings\" allows the user to store the detectors current settings along with a simple name tag for use on a future return trip. The detector can store dozens of these stored settings.

A note pad memory is also provided for the user to enter the GPS location next to the name tag. This allows the instant recall and loading of all the detectors settings for any particular site.

The detector's settings are stored automatically when the detector is told to

shutdown. Turning the detector back on reloads these settings.

The memory's used are all non volatile types. The will store their data without a battery being installed in the detector.

SHUTDOWN

The Pulse Devil uses a software shutdown. Selecting \"Shutdown\" causes the detector to load its settings into memory and then shut off the power from the battery via an electronic switch.

An audio low battery alert sounds a sharp beep once every thirty seconds until the critical battery voltage is reached and the detector shuts down to avoid over discharging of the battery pack.

The Pulse Devil has a built-in battery charger. An AC cord and a car cigarette lighter cord / plug provide charging from 90VAC to 240VAC 50/60Hz or a 12VDC to 24VDC vehicle battery.

The battery pack can be charged in place or simply replaced in the field.

For the European or the deluxe versions, there is also a Target ID or TID.

The LCD display now displays the target ID in super large, easy-to-read numbers. The number is negative for ferrous and positive for non ferrous.

The TID provides the same number for the same type of target just as the TID

circuits found on many high end VLF detectors do. The TID is quite accurate.

As a final note, the Pulse Devil in the picture that is posted on the forum does not have the graphics on it as the production model will.


Here is an explanation of some of the Pulse Devil's features. This explanation is not to be considered as a part of an operating manual.It is only an explanation of some of the features.

PULSE DEVIL: ADDITIONAL INFORMATION

DISCRIMINATION

All versions of the Pulse Devil come equipped with a full range discrimination control. This control, although set digitally,operates in exactly the same way as a discrimination control on a VLF.

For prospecting a full range, discrimination is not useful. The only discrimination required is one that provides a ferrous - nonferrous indication.

The full range discrimination control is provided to allow the detector to be used for coin and relic hunting in addition to its use in prospecting.

The discrimination control settings start at iron rejection and goes to foil rejection and then all the way up to pulltab rejection.

The Pulse Devil can be upgraded by the dealer to include a Target ID or \"TID\". The European version of the Pulse Devil is designed primarily as a coin and relic detector — the TID is included on this
model.

The TID will output a negative number for a ferrous target and a positive number for a nonferrous target.

Each type of target will provide a different number.

The numbers are a measure of the targets conductivity.

Low conductivity targets such as cupro nickel coins will provide a low number such as +50 while a high conductivity target such as a silver coin will provide a higher number such as +180.

The numbers displayed in TID mode are much taller and easier to read than the characters in other modes. Each number takes up the entire display height

NOTE: The dealer can also change the display for left handed operation. This is accomplished by turning the display 180 degrees.Left hand Pulse Devils will have their master control knob on the
right of the control panel while right hand Pulse Devils will have their master control knob on the left.

PULSE WIDTH SELECTION

There are four selectable transmit pulse widths. These are 250us,
500us, 750us and 1000us. Almost all other PI detectors use transmit pulse widths of between 50us and 250us. Some use both long and short pulses. The maximum pulse widths used are on the order of 250us. (us = microseconds or millionth parts of a second).

Each type of target has what is called a time constant or \"TC\". This is a measure of the time it takes the received signal to decline in voltage from its peak value to a low value.

Small gold nuggets can easily have a TC as low as 15 microseconds while a large silver coin might have a TC of many hundreds of microseconds.

In order to achieve a maximum detection depth on a target, the width or length of the transmit pulse should ideally be long for long TC targets.

A target such as a small gold nugget can be detected at maximum depth using a transmit pulse which is much shorter. Using a long pulse on a target with a short TC will neither increase or decrease the detection range.

The selection of the pulse width is now dependent on the type of target that is being sought. In an area where only small gold has ever been found the 250us setting is ample. Conversely, if the area has produced large gold then it is safer to use a longer pulse width.

The highest pulse widths are required when searching for large highly conductive targets such as large silver items.

Using longer transmit pulses causes the battery to be drained faster than when shorter transmit pulses are used. This is the reason that a selection of pulse widths has been provided.

GROUND ADJUST

The ground adjust control is used the same way as the ground adjust or ground balance controls on many VLF detectors. The searchcoil is simply lowered toward the ground from an initial height of two to
three feet or 60 - 90 cms.

If the audio level increases, the control is turned counterclockwise.

If the audio level decreases, then the control is turned clockwise.

The detector is tuned to the ground when the change in the audio level is the least when the searchcoil is raised and lowered.

AUTOMATIC TUNING

The retune speed of the Pulse Devil can be adjusted from a super slow speed of 25 seconds to a super fast speed of 1 second.

There are two different tuning modes provided. A regular automatic tuning or a zero overshoot constant threshold tuning is user selectable.

The tuning speed is selected for the users preference or to minimize any ground noise due to rapid variations in the mineral make up of
the soil.

MORE TO COME
Dave

Thanks Doug for posting the \"In's and Out's\" of what the Pulse Devil 1000 has on offer. Since you brought Dave E's Pulse Devil into the limelight on your forum each posting with any reference to this Pulse Induction detector has transfixed me.

If you could excuse my ignorance within all the PD postings on your forum but has any reference been made regarding the PD's pulse train.

Therefore am I correct to believe the PD is a \"Single Pulse\" train type detector and not a \"Multi Pulse\" train type such as the (1) long pulse and (3) or (4) short pulses used within a pulse train on our Minelab PI's ?

Gary.

Gary you are correct.The PD does not use a pulse train as per a ML.It is totally different beast to a ML in almost every aspect.For example it can sample down to about 1-2usec after pulse termination! The \"gold\" std is considered to be 10 u secs and 5u secs the \"diamond\" std for \"fast coils\". Its signal processing,GB method and discrimination methods are totally different to ML and I suspect have never been used before on any Pi detector. The key to what it does is the induction balance coil system using co axail co- planar coils and the very unique ultra low noise analogue circuits that are controlled by two MPU's.
Doug

Thanks again Doug and I am not sure if you have a background in electronics but you know far more than myself, that I am certain of. As is my usual practise I have to refer back through postings I have saved of forums, from those in the know, for the purpose of my knowledge.

Now if I refer and bring back to light an old posting under the heading MINELAB PATENT with subheading SD’s Patents and Theory written by Jim S on Eric F’s forum. Jim tried a simple explanation of Bruce Candy’s patent theory behind the \"Multi Pulse\" machine which constituted one of the biggest landmarks in PI signal processing. Also Jim mentions \"Ferrite\" decays in mineralized ground and the implication that more pulse length results, the greater the chance of finding weak metal targets in a basically ferrite volume. In other words the gold response may be hidden in the decay of a LONGER pulse but suddenly manifest itself in the shorter ferrite decay of the SHORT pulse.

Again if I may and pluck another reference this time from a reply by Robby H to the Minelab Patent posting by Jim S. Rob said Candy’s bi-polar pulse in the GP is more about canceling previous ground sampling history and avoiding saturation than making false claims as some believe, tho it is obviously also a very good way of canceling noise and improving gain at the same time and has always been the preferred method in his patent.

Dave Emery also had his say when he started an interesting discussion on Eric's forum under another heading Minelab SD's and GP as he was trying to describe an easier understanding of Candy's patent.

From the small sections I have cut and pasted here from the original postings in the Minelab Patent discussions, I am now wondering how much of what has been said above will effect the PD1000's success in our ground types.

Hopefully that answer is not far off when our Aussie testers with the PD try it out over goldfield ground in Victoria, West Australia and Queensland.

Gary.

Daves method of ground cancelling is totally different to ML because he uses IB coils. To get some idea of what he does have a look at Allan Westerstens Patent on the Goldsweeper.The essence of the method is to separate the reactive ground signal(ferrites) from the resistive target signal using pulse on and off sampling and signal processing.The PD also uses a totally different method of sampling and signal processing.

But how this system will go over our worst ground I guess is the very key question. But the PD does have a very wide range of retuning speeds, Rx gain and the sample delay can be varied from 1-25 u secs so this should enable it to cope with our bad ground. Time will tell. The essence of the candy method is that the ground decays as 1/t t=pulse length whereas a target decays exponentially.Therefore the ground ferrites decay diffrently at each pulse length but conductive target decay is independent of Tx pulse length. This is a gross over simplification as the Candy patents are probably the most difficult to figure out. A lot in the patents is not explained and there is a lot I think left out.
Doug