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PTC-3 Passive Trail Counters - Users Guide

The PTC-3 is an advanced yet inexpensive counter for keeping a relatively accurate tally of the number of people passing by a certain point. It was designed to address many of the existing problems inherent in determining usage levels on hiking trails and walking paths. As a narrow-field passive infrared counter, the PTC-3 does not require an infrared beam to be broken, and does not generate one. Instead, it simply "sees" warm moving objects passing by. For studies of trail usage, this method has a number of distinct advantages:

-Battery drain is drastically reduced. Battery life is estimated to be five years or more (10 years for units previous to number 10101314).*

-With frequent battery changes eliminated, the case seal remains secure and undisturbed.

-A problem with the old beam-break units was their very narrow field (since the beam must be focused) which caused a tendency to count unwanted small objects. Our sensor, on the other hand, is deliberately defocused to a calibrated degree so that it sees and counts a single "blob" of infrared whenever someone walks by, with just enough resolution to allow it to discriminate between closely spaced walkers. Extra counts caused by swinging arms and the like are virtually eliminated. Both radiated and reflected infrared will trigger the counter - it is simply looking at the scene in front of it with its infrared "vision".

-Unlike wide-field passive counters, the PTC-3 is able to count very closely spaced trail users even when they are travelling at considerable speed, such as runners or bicyclists.

-Aiming the unit is simple since it does not require alignment of light beams, mirrors or reflectors.

Testing the Unit
-The unit will be shipped powered-up and connected to its SIS-3 spot infrared sensor. It will function as soon as it is taken out of the shipping package and allowed to autorange on a background scene for about one or two minutes. Full sensitivity may take 5 minutes or so to achieve. The display may be indicating a large number when received due to cable microphonics during shipping.

-Place the SIS-3 sensor on a table indoors or in any convenient outdoor location. Reduced range may be experienced indoors or with a warm or hot background scene outdoors.

-A count seen on the display a short time after aiming the detector indicates "autorange nearly complete".

-If this is not seen, the unit may be already fairly close to the correct background setting.

-Wait several seconds more as the unit fine-tunes itself to the existing background scene. More counts may be seen.

-If the unit continues counting indoors when nothing is in front of it, find a location where less movement of warm air exists.

-To test the unit, sweep your hand in front of the detector. It should correctly count the number of hand sweeps. Rapid multiple sweeps of the hand in a short time may seem to cause the unit to lag behind in its counting activity but it should still read the correct total number a second or two after the hand sweeps stop.

Mounting the Sensor
-The SIS-3 sensor should be mounted about 1 meter back from the path of the closest expected person to be counted. If a person pauses in front of the unit for several seconds and then moves away, the 1 meter minimum helps to prevent double counting. The useful range of the unit extends out to about 5 metres in front of the sensor, or even more if the background scene contrasts well with the subjects at IR wavelengths. The trail thus may be 4 metres wide at the point where people are counted. However, a narrower path will help reduce the number of people walking side by side and thus make it easier for the unit to sort out individual people for counting.

-Aim the unit's aperture across the trail at about waist level for the average person. The background scene in front of the detector should be an area which remains relatively cool and shaded and does not contain objects which may be heated by the sun and moved about by the wind - these may cause false counts. Vehicles may also cause false counts.

-There is little one can do to prevent large animals such as deer from triggering the counter - they tend to prefer trails rather than bushwhacking, just as humans do. However, this could be used to advantage for wildlife photography as these units may be custom-equipped or modified to trigger a camera. Increasing the sensor height can allow some animals to walk under the detection zone without triggering the counter - but may cause the counter to miss small children also.

-It is a good idea to hide the unit from the public and protect it from vandalism, theft and unauthorized reset. Some customers have found that a hole drilled in a dead tree is an unobtrusive mount, particularly if the unit is looking out through a natural knothole in the trunk of the tree. One park ranger placed his SIS-3 sensor in a crevice on the side of a large boulder, under moss which he managed to avoid disturbing. A 1 cm. hole, or slightly less, is all that is needed to provide a view for the sensor. The three metre cable allows the display to be read conveniently when the sensor itself is concealed in a variety of different types of locations.

Operating Tips
-Do not strike, shake or rattle the remote sensor cable while in operation or false counts may be generated by cable microphonic action, a tradeoff resulting from the extremely low battery drain of this type of counter.

-This implies that the counter should not be used as a hand-held unit. It is preferable to strap it down with something or at least place it where it can be read without physically moving it.

-The recommended times to allow for autoranging are: 5 minutes if the sensor has moved; 10 minutes if the sensor has been unplugged; 20 minutes if the battery has been replaced. It is not necessary to add these times together. Often, good operation will be seen in much less time.

-To reset the counter to zero, gently push the zero button by inserting a ballpoint pen into the small hole near the LCD display. Use of a sharp object to reset the unit to zero may puncture the seal membrane and let moisture in.

-There is no on-off switch. The battery should last for five years or more. See bottom of page 3 for replacement instructions.

-Battery life will not be extended very much further by unplugging the sensor. Although it contains a preamplifier which draws current from the battery, this current is only about 1 microamp. The battery's shelf life may be the limiting factor.

-The sensor unplugs effortlessly from the counter by rotating the lock ring a few degrees counterclockwise and pulling the plug straight out. Do not try to rotate the entire plug. It has three pins which engage with three holes in the socket and it will not turn.

-The sensor must be properly plugged into the counter and the lock ring must be engaged when the unit is left exposed to the weather. A small O-ring installed on the sensor cable plug is part of the unit's weather seal. Shake any excess water off the plug and dry it with a rag or tissue before plugging it into the counter after site installation, and in bad weather try to do the installation without unplugging the sensor, I.E. by putting the sensor in place from the rear. If the zero-button membrane is
found to be pressing the button down after transporting the counter to a lower altitude, remove the sensor plug for a few minutes under dry conditions to equalize the interior of the case with atmospheric pressure.

-When storing the counter, keep the sensor connected or wrap the counter in aluminum foil to protect it from static discharge. The unit's high (640K) input impedance drains away minor static charges quickly but cannot cope with a large static spark.

-Do not hand the trail counter to someone through a vehicle window unless the sensor is plugged into it, or unless you momentarily touch the other person's hand first to drain off any static electricity generated by the movement of the vehicle. With the input open, static electricity from the vehicle could damage or destroy the counter. This applies to any conveyance with rubber tires. A helicopter is usually static free when metal landing gear is in contact with the ground. An example of a situation where static electricity from a helicopter could be a problem is when it is discharging or taking on passengers and equipment while semi-hovering with the front of the landing gear resting on a dry piece of wood elevated off the ground, a method occasionally used when no flat landing pad exists. To reiterate: if you have left the sensor in its field location for any reason and have only the counter itself to hand over, ground yourself out to the person receiving the counter before passing it to them. Metal doors and carpeted rooms are another familiar source of damaging sparks.

-In about 2 per cent of existing installations there have been reports of insects placing foreign objects in the SIS-3 sensor's light pipe and preventing counting. This may be prevented by placing a single layer of ordinary kitchen plastic wrap over the end of the light pipe, stretched enough to smooth out most wrinkles. Range may be slightly reduced. We ship these units with open light pipes to maximize optical performance but in many installations full range is not required. It is possible to clean out
insect debris with a piece of wire, but do not remove the black substance covering half the window at the base of the pipe, or the sensor will not work. There is a chance of salvaging a sensor with the black substance gone, by forcibly pulling out the light pipe and replacing the black material with General Cement Liquid Tape, coating half the window only. Look for traces of the old coating in order to coat the same half of the window, then let dry and push the light pipe back in place.

Questions and Answers/Troubleshooting
Q. Why does the counter register extra counts when the sensor cable is shaken? Is there a loose connection?
A. No. To get this kind of battery efficiency we are using high-impedance circuitry and relatively low signal levels. For this reason the cable can act as a "condenser microphone" and pick up the sounds created when you shake it around.

Q. My counter registers a count when I brush my hand over it, when the sensor is not even plugged in. Why?
A. With the sensor unplugged, the counter's input is not shielded against static electricity. When you brush the case with your hand, you can sometimes generate static charges faster than the counter's input can drain them off, and a count may be generated. This characteristic may be put to use (gently) to get the counter off zero so you can test the zero reset button when no sensor is available.

Q. I pointed my counter's SIS-3 sensor at a wall in my office. It was only 6 inches from the wall. Nothing could have passed in front of it but several hours later I noticed that the counter had counted up to quite a large number. What was it counting?
A. The sensor was probably picking up reflected infrared off the wall, and counting people walking in other parts of the room.

Q. How can this unit trigger a camera? I don't see any camera connection on it.
A. In normal units the camera trigger connection is not brought out through the case, in order to reduce potential weather-seal problems and exposed connections. Also, additional equipment is needed to trigger a camera. All of our counters generate special camera-trigger signals as the subject enters the sensing area, unlike the counting function which counts subjects as they leave. On a custom basis these signals can be brought out through the plastic case, amplified externally and adapted to particular cameras.

Q. How do I change the battery if it goes dead?
A. Since February 2002, All PTC-3 counters have been equipped with a soldered-in battery. We recommend sending the unit in to us if it appears to have a dead battery (no numbers appearing on the display). Older units with the battery in a holder will be upgraded to a permanently soldered-in battery if the old battery is dead. It is important to note that if the unit is less than ten years old, a dead battery may be a sign of other problems such as a short circuit in the cable leading to the sensor. Copies of this user's manual prior to this revision give directions for disassembling the unit and changing the battery; this is no longer recommended.

How the PTC-3 Counter Was Developed
In the mid 1990's, staff at Mount Robson Provincial Park in British Columbia were looking for alternative ways to do studies of how many people were using various trails over a given period of time. They had in many cases been flying car batteries by helicopter to remote back-country counting sites every few weeks, which was very expensive. Carson Electronics was approached to see if we could come up with a reliable type of trail counter that used less battery power to operate.

First, we tried to upgrade the traditional beam-break counter to take less current. Results were moderately good. (other companies have since achieved a 1 milliamp battery drain on these by using pulsed beams - about a 200 to one improvement on earlier types and better than our beam-break experiments achieved).

Bypassing the pulsed-beam concept, we decided to eliminate the light beam altogether, by sensing the existing infrared image in front of the counter. We chose to keep as much as possible of the optical geometry of the old beam-break counters intact. The first unit, dubbed the PTC-1, achieved 1 milliamp battery drain at 6 volts, but was fussy to adjust and rather unreliable, since its autoranging abilities were entirely optical while the electronics needed to be manually adjusted. The idea did work, however, so a number of modifications and improvements were made to the sensor to enhance its optical autoranging abilities and clean up its output signal. Also, an electronic autoranging system was added to the counting circuitry to fine- tune for any variations in background infrared that managed to get past our optical autoranging system. The counter now worked so well that we decided then and there to start marketing the unit, as the PTC-2.

As the technology began to be used in the field we received feedback from users and made further changes. Stability was further improved and by 1997 the changes were retrofitted free of charge into all the early units. Even the original one-of-a-kind PTC-1 was retrofitted with PTC-2 circuitry and remains at work in the field to this
day. Most customers indicated they would like to be able to count in one location and read the display in another, so we stopped putting the detector in the same case as the counter and began placing it at the end of a 10 foot cable, where it became the SIS-1 spot infrared sensor. Changes in light pipe geometry led to the improved SIS-2, and the addition of a metal shroud around the active part of the sensor created the SIS-3. By 1998, SIS-2 and SIS-3 sensors had been provided for all existing PTC-2's and their internal sensors had been removed. The PTC-2 was about 6 by 6 by 3 inches in size and ran on a 6 volt lantern battery. Battery drain was still about 1 milliamp and batteries lasted about 3 months. The LCD display had its own additional batteries specified to last 7 to 11 years.

There followed an all-out effort to maximize reliability and reduce battery drain in our counters. Using ultra low power technology and a smaller LCD display, we were able to operate the entire unit - sensor, counting circuits and LCD screen - on a single onboard lithium cell while reducing power requirements to around 8.5 microamps at 3 volts - a startling 94,000 to one reduction in power requirements compared to BC Parks' old 12 volt, 200 milliamp trail counters. We found ways to run our tried-and-true SIS-2 and SIS-3 sensors at reduced power levels, and get slightly cleaner signals from them at the same time. This allows PTC-2 users to upgrade without
pulling the sensor out of the spot where they've cleverly hidden it - The existing sensor will work just fine, in fact better than ever, as part of the new system, and is identical to all sensors built since. We decided that, despite the infinitesimal power requirements of the new circuitry, we would use a relatively large lithium cell of one ampere-hour capacity to power the system. We estimate battery life to be well over ten years. Signal amplification and filtering is another area of improvement, embodying all we've learned about trail counting over the years. In addition, the much "quieter" electrical environment within the counter circuitry, due to the very low battery drain, enables the PTC-3 to correctly sort out and count each person exactly once under remarkably difficult conditions. Case size has been greatly
reduced also, mainly due to the elimination of the large battery which powered the PTC-2 units. The result is the PTC-3 trail counter which has been our most popular product ever, by a margin of more than ten to one.

All PTC-3's manufactured since October 2000 contain a PTC-4 circuit board - the same counting circuitry as that of earlier boards but with space provided for time/date stamping and data download capability to be retrofitted if desired in future. We continue to respond vigorously to any problems reported by users in the field.

In early 2002 we began using soldered-in batteries and eliminated the battery holder from the PTC-3 design. At the same time we implemented a change in case sealing technique to eliminate the possibility of sealant fumes being trapped inside. These improvements were made as a direct result of the discovery of battery holder contact problems in some units.

We welcome any and all comments and suggestions.

The PTC-3 trail counter and SIS-3 spot infrared sensor are both warranted for 15 months from date of purchase against failure to count accurately due to defects in materials or workmanship. In the event of such failures, Carson Electronics will repair or replace the defective unit at our expense. This warranty does not include shipping costs from the customer to us, nor does it include failure to count accurately due to physical or electrical damage (except where such damage is deemed to have occurred on the premises of Carson Electronics before the unit was delivered to the customer), the effects of weather including lightning discharges, unsuitable background scene or other conditions of the installation site. Failure of two or more counter/sensor combinations to count properly at a given site, where both units are later found to work properly in our tests, will be deemed to be an indication of an unsuitable site, and such failure will not be covered by this warranty. Requests for warranty repairs must be made by phone or email and our authorization must be given prior to shipping the unit to us for such repairs. We will pay for return shipment costs back to the customer after warranty repairs.

Telephone/Fax: (250) 566-4694

*NOTE: as stated on our home page, the estimated battery life of the PTC-3 trail counter is now five years rather than ten years, due to a change in the type of technology used by Red Lion Corp. in their small LCD screens that are used in the PTC-3. I suspect that they lost their source of the main microchip they were using in these displays - it was probably discontinued by the manufacturer or was something that was custom-made in a certain quantity that finally ran out. To Red Lion's credit, their engineers developed a new type of display that fits where the old ones did and operates almost identically, so no system using their displays was left stranded. However they were not quite able to match the extreme low power consumption of the original units.