Your RF Cafe
July 1962 Popular Electronics[Table of Contents]
People old and young enjoy waxing nostalgic about and learning some of the history of early electronics. Popular Electronics was published from October 1954 through April 1985. All copyrights are hereby acknowledged. See all articles from Popular Electronics.
In "The River Sniffer," our intrepid sleuthing heroes Carl and Jerry apply their electronics prowess and lessons remembered from chemistry class in order to catch polluters who are dumping chemicals into the river where they like to fish. I always like being reminded of something long forgotten when reading an article, and this one did not disappoint. Do you recall what 'pH' stands for as a measure acidity or alkalinity? It means 'potential Hydrogen ion concentration.' Don't thank me if it jogged your memory as well - thank Carl and Jerry.
A Carl and Jerry Adventure
By John T. Frye
This is the life," Carl sighed contentedly; "no lessons, no exams, no ROTC drills, no nothin'!" He and his friend, Jerry, were sprawled on their backs on the river bank staring upward through the sycamore leaves at a buzzard sail-planning in the cloudless summer sky above. Down at the edge of the water, two fishing rods rested in a couple of forked sticks.
Before Jerry could answer, a slight splashing from the river attracted his attention. Raising himself on one elbow so that he could get a better look, he exclaimed, "Hey, Carl, look at those fish on top of the water!"
Two large bass were threshing about on the surface, obviously in their dying throes. Even as the boys watched, the splendid fish turned belly-up and floated quietly downstream; and, looking more closely, Carl and Jerry saw that the two were accompanied by other dead and dying fish of various sizes.
The throbbing of an outboard motor was heard downriver, and an aluminum boat carrying a young man dressed in a game warden's uniform came in sight around a bend in the stream. When he saw the boys, he ran the bow of the boat up on the bank, cut the motor. and stepped out.
"That's a mighty sorry sight," he remarked, motioning toward the floating fish. "I'd certainly like to catch whoever keeps dumping that fish-killing stuff into the river."
"You mean it has happened before?" Carl queried.
"About once a week all spring, but not always on the same day or night. When someone calls in and reports dead fish, I get right on it; but I never know how far the fish float after dying. However, this is the farthest upstream I've found them, and some of those fish are still wiggling. This time, at least, the stuff must have entered the river from this bank and not too far upstream; but I've covered every foot of the river for five miles in either direction without finding a single likely source of pollution. If only I had some way of knowing just as soon as the stuff hit the river - even before the fish began to die - I'd stand a chance of tracing it. At least I could collect a strong enough sample for accurate analysis before the polluting substance was too greatly diluted."
Jerry was looking very interested.
"You mean you need some kind of a robot to sample the river
water continuously and give some sort of alarm when an unusual
amount of destructive chemical floats past it ?"
"Exactly, but I guess there's no such gadget."
"Don't make book on it. I have an idea: if you'll take that glass jug lying in the weeds across to the other side of the river and fill it, my friend here and I will try to build such a robot for you. Electronics is our field. I can't promise anything, but you can give us your telephone number and we'll call you if we come up with something."
"Okay, what have I got to lose? But what do you want with the water?"
"We'll need a sample of normal, unpolluted river water to
While Bill Herber, the game warden, was collecting the water, Carl and Jerry reeled in their lines. A half hour later they were entering the coolness of their basement laboratory at Jerry's home, and Jerry went straight to a stack of papers resting on a shelf. He sorted through them until he found what he sought.
"Ah, here it is," he said. "I was sure I had saved the description of the River Robot Monitor that Mr. Edward J. Cleary, Executive Director of ORSANCO, sent me."
"Bully for you; so what is it?"
"It's a unit of a system of continuous automatic electronic
river pollution monitors used by the Ohio River Valley Water
Sanitation Commission to keep a continuous check on the Ohio
River water. Eleven of these unattended robot devices are strung
along the river. They constantly test the water for seven different
variables: dissolved oxygen, chloride, hydrogen ion, specific
conductance, oxidation-reduction potential, temperature, and
solar radiation. The various sensors feed their information
into a telemeter transmitter at each location, and all the transmitters
are connected by telephone wires to a telemeter receiver in
Cincinnati. At regular intervals this receiver calls each monitor
for a report. Signals received actuate a transcriber which automatically
types the information on tabulation sheets for diagnosis of
"So that's why you told Mr. Herber not to bet there wasn't a river robot monitor! We're not going to try to build one of these robots, are we?"
"Hardly. They're quite complicated and cost a lot of money. But I'm hoping we can build a simple gadget based on a single sensing unit that will serve our purpose."
"How about the hydrogen ion measuring part? If I remember my chemistry, that's an indication of the acidity of a solution."
"Either the acidity or alkalinity of the solution," Jerry corrected. "If you recall, the potential hydrogen ion concentration, or pH factor, is measured on a 0-14 scale, with 7 being the number associated with 'pure water.' Numbers going downward from 7 indicate increasingly acid solutions. Readings going upward from 7 indicate increasingly strong base solutions. Since the number is actually the negative logarithm of the hydrogen ion concentration, each pH unit represents a ten-fold change in solution strength. Compared to a pH 5 solution, a pH 4 solution is ten times more acid, and a pH 3 solution is a hundred times more acid.
"One way to measure the pH of a solution," he continued, "is to add special organic indicators and observe the color change that results. A better method, in many respects, is to employ an electro-metric device that translates the pH of the solution into a reading on a meter whose scale is marked off in pH units. That's the kind of pH indicator our chemistry prof at Parvoo University used in his lectures last year."
"Fine. All we have to do is build a pH meter and let the meter-deflecting current also operate a sensitive relay that will sound an alarm."
"It's not that easy," Jerry demurred.
"Until I read this pamphlet called 'The Development of pH
Instrumentation' by A. O. Beckman of Beckman Instruments, Fullerton,
California, I had a hazy notion a pH meter was a relatively
simple gadget that employed either a current conducted through
the solution or a voltage produced by galvanic action on electrodes
immersed in the solution to deflect a meter. Actually the latter
principle is the one employed, but both the electrode used and
the indicating meter are very special types.
"Oxidizing of ordinary metallic electrodes immersed directly in the solution prohibits their use; so a special 'glass electrode' is employed. Picture an electrode surrounded by a low-resistance, non-oxidizing solution in a test tube that's immersed in a solution being tested. The test tube wall keeps the solution being tested from oxidizing the electrode, but a voltage appears across this glass membrane which is proportional to the difference in hydrogen ion concentration of the solution on either side. As you can guess, this glass electrode is an extremely high resistance device, and special means are necessary to measure the voltage developed. In practice, a not-too-simple feedback amplifier translates this voltage into meter-deflecting current."
"Say no more; we'll not try to build a pH meter. Got any other ideas?"
"Yes. We know that the presence of acid greatly influences the conductivity of a solution. What say we build a simple bridge circuit in which two legs are fixed resistors, a third leg is the resistance appearing between two electrodes immersed in the river, and the fourth leg is a variable bridge-balancing resistor in series with a special temperature-sensitive resistor also in the water? We can drive the bridge with a few volts of a.c. produced by a simple transistorized chopper."
"Why the temperature-sensitive resistor and why the a.c.?" Carl wanted to know.
"D.c. would quickly polarize our electrodes and render them useless," Jerry replied. "Also, conductivity changes considerably with temperature, and we want our device to respond only to chemical change; so we must compensate the bridge for the effect of temperature change in the river water. A little battery-powered transistorized amplifier will magnify any a.c. voltage resulting from bridge unbalance.
"This amplified output can be rectified with a diode," Jerry
went on, "and used to drive a meter and a sensitive relay connected
in series. An increase or decrease in the conductivity of the
water flowing past the electrodes will unbalance the bridge
and cause the relay contacts to close and the meter to read
upscale. Closing of the contacts can sound an alarm."
"Sounds good; let's try it," Carl said, rubbing his hands impatiently.
Like most electronic devices, the "river sniffer," as the boys dubbed their brain child, was not nearly so easy to put into practice as it sounded in theory. They spent three full days building a really stable transistorized amplifier, finding the proper thermistor to keep the bridge balanced during a 20° temperature change in their jug of river water, and adjusting the sensitivity of the relay so that it remained open with the electrodes in a weak salt solution but closed when the solution was weakened with more water or strengthened with a little more salt. Finally, though, they were partially satisfied with the operation of their invention - a good technician is rarely completely satisfied - and they called Mr. Herber.
He drove them to a farmhouse where he kept his boat, about a quarter of a mile upstream from where they had met him. The river sniffer, housed in a weatherproof box, was installed on the river bank; and the sensing electrodes were placed well out in the current. Jerry carefully balanced the bridge with the aid of the indicating meter.
A bell was installed in the farmer's house and connected with a bell transformer and the contacts of the sniffer's relay so that the closing of the contacts would ring the bell. Then, after extracting a promise from the farmer to call Mr. Herber immediately if the bell rang, they left the robot to its sentry duty.
It was shortly after midnight that same night when Jerry's telephone rang.
"Hi," said the voice of Mr. Herber, "the farmer says that gadget of yours is ringing the bell off his wall. Want to go along and see what's up?"
"Sure," Jerry answered. "I'll get Carl, and we'll be out front waiting for you."
It did not take long to reach the farm.
The farmer, clad in his nightshirt, was sitting in his kitchen
malevolently eying the clanging bell on the wall. Jerry disconnected
it; the farmer went back to bed; and the boys and the game warden
walked down to the river sniffer.
"Wow!" Jerry exclaimed as he lifted the lid and glanced at the meter reading with the aid of his flashlight. "Something is really boosting the conductance. What say we take the sniffer with us in your boat and see if we can't run down the source of the pollution?"
In a few minutes they were heading upstream. Jerry was in the bow with his sniffer; Carl was in the middle; and Bill Herber operated the outboard motor at the stern. As the boat moved to the middle of the river, the meter reading declined; but swinging back toward the bank pushed it higher than ever. It continued climbing slowly until they were about a quarter of a mile upstream; then suddenly it dropped to the bridge-null value.
"Back up," Jerry said; "we've run out of it."
Mr. Herber reversed the boat's direction, and the meter reading shot upward. The game warden then maneuvered the boat under Jerry's direction until it became apparent the polluting substance was coming from beneath some low-hanging bushes growing on the bank. Suddenly he revved up the motor and headed straight for these bushes. As the boys ducked, branches scraped along the metal hull and the boat emerged in a shallow creek whose mouth had been concealed by a thin screen of willows.
"Better watch your propeller," Jerry warned as he peered over the side with his flashlight; "the water's not more than a foot deep."
"No sweat," Mr. Herber replied. "This motor doesn't have a propeller. It operates on a jet principle and will run in four inches of water."
At this moment Jerry spied a trickle of water dribbling from a large tile set in the bank of the creek, and a little checking with the river sniffer confirmed that the water pollution was coming from this tile.
Bill Herber stepped out of the boat and motioned for the boys to follow him toward a large concrete building a short distance away. A light was shining from the windows and through the open door, and inside they found a young man busily pouring some liquids from carboys into a large vat.
When Mr. Herber explained the reason for their visit, the young man shook his head ruefully. "I'm afraid I'm the one you're looking for," he admitted. "The first of the year I started a little plating business here. I use sulphuric acid to clean the parts before putting them in the plating bath. About once a week I flush the dirty and weakened acid down that sewer that leads into the crick and mix up a new batch, as I'm doing now. I never thought about killing fish or causing any other trouble, and I can assure you it won't happen again."
"I'm sure it won't," Mr. Herber said kindly, "but I'll have to report it, and there's a fine for river pollution. I hope they go easy on you. Come on, boys; let's get back to town."
As the game warden drove Carl and Jerry home, he declared, "I sure do appreciate what you fellows did for me. I don't know how to thank you. I wish I had brains enough to build something like that river sniffer of yours."
"We lucked out," Jerry said modestly.
"Had it been something other than a strong acid that was killing the fish, the sniffer might not have worked so well. And as for paying us, how about showing us a spot where we really can catch some fish?"
"That I can do. Be ready with your rods and a can of stinkworms about four o'clock tomorrow afternoon, and I'll show you the best channel-cat fishing east of the Mississippi!"
Carl & Jerry: Their Complete Adventures is now available. "From 1954 through 1964, Popular Electronics published 119 adventures of Carl and Jerry, two teen boys with a passion for electronics and a knack for getting into and out of trouble with haywire lashups built in Jerry's basement. Better still, the boys explained how it all worked, and in doing so, launched countless young people into careers in science and technology. Now, for the first time ever, the full run of Carl and Jerry yarns by John T. Frye are available again, in five authorized anthologies that include the full text and all illustrations."
Carl & Jerry Episodes on RF Cafe
- Carl & Jerry: Anchors Aweigh, July 1956
- Bosco Has His Day, August 1956
- The Hand of Selene, November 1960
- Feedback, May 1956
- Abetting or Not?, October 1956
- Electronic Beach Buggy, September 1956
- Extra Sensory Perception, December 1956
- Trapped in a Chimney, January 1956
- Command Performance, November 1958
- Extracurricular Education, July 1963
- Treachery of Judas, July 1961
- The Sucker, May 1963
- Stereotaped New Year, January 1963
- The Snow Machine, December 1960
- Extracurricular Education, July 1963
- Slow Motion for Quick Action, April 1963
- Sonar Sleuthing, August 1963
- TV Antennas, August 1955
- Succoring a Soroban, March 1963
- "All's Fair --", September 1963
- Operation Worm Warming, May 1961
- The Crazy Clock Caper, October 1960
- Two Detectors, February 1955
- Tussle with a Tachometer, July 1960
- Therry and the Pirates, April 1961
- The Sparkling Light, May 1962
- Pure Research Rewarded, June 1962
- The Hot Dog Case, December 1954
- A New Company is Launched, October 1956
- Under the Mistletoe, December 1958
- Electronic Eraser, August 1962
- Blubber Banisher, July 1959
- "BBI", May 1959
- Ultrasonic Sound Waves, July 1955
- The River Sniffer, July 1962
- Ham Radio, April 1955
- El Torero Electronico, April 1960
- Wired Wireless, January 1962
- Electronic Shadow, September 1957
- Elementary Induction, June 1963
- He Went That-a-Way, March1959
- Electronic Detective, February 1958
- Aiding an Instinct, December 1962
Posted November 18, 2013