Until a few weeks ago, I thought all the Nielsen families lived in Alabama in kudzu vine-covered cabins with washtubs and Chevys in the front yard and tall antennas on what remained of the roof. I blamed them for the bionic plague and the family feud and watched whatever I pleased on my private tube.

Publicly, I pretended to view only educational channels and a few ofthe better specials on the networks, while privately I sated myself on "Partridge Family" reruns and old "Emergencies" in lieu of the news. Saturdays started with "Pink panther" cartoons and ended with "All Night Movie" on Channel 5. I was responsible to no one.

That all changed when the man from Nielsen came to my partially renovated townhouse in a partially fashionable Northwest neighbor-hood and offered me rating power. I had been chosen to join the cozy Neilsen clan of computerized television viewers.

Of course, I was honored, but I was also afraid. How had they learned about my addiction? Did a Neilsen agent lurk outside my window looking for the telltale fluorecent flicker? Or worse yet, had I been recommended by someone who knew my secret shame? No, it was nothing like that, nor my age, sex, color or liberal tendecies. It was my address, said the Nielsen man, who assured me, "It's very scientific."

"If you decide to go along with us, there'll be just a few questions you'll have to answer," he added, forcing me to reveal the actual age of my Volkswagen, how far it got or didn't get in college and how many hours I worked per week. I told him I only worked about two hours a week, but he put down 40 - not a very flattering misunderstanding.

Next, he made me promise never to reveal that I was a part of the Nielsen family. Specifically, I must avoid all contact with network employees and television critics. I took the oath of secrecy.

With that, he was off, promising to return at a mutually convenient time with many mysterious boxes and wires for my TV set. On the designated day, he arrived promptly and said: "You people sure have a lot of work to do on this house. Sensing my disfavor, he went to work and in just two hours installed a couple of boxes and about 50 feet of wire that's twisted untidily around the outlet that provides the juice for the extravaganza.

Sometimes the whole mess gurgles and whirs and scares the cats, who simply wanted to watch Morris be finicky.It scares me, too. For all know, it could be an instrument of the federal bureaucracy, the CIA or agents of TV Guide, all of whom may be doing an expose on the viewing habits of the armchair liberal.

you get $25 when you sign on, plus $1 month for every TV in the houe. Nielsen will also pay one-half of the cost of repairs should the set break down while you're a family member. In addition, you get a $25 gift certificate in a plain, brown wrapper that you may use toward the purchase of another television shoud you wish more cable and boxes for your home.

On top of all that, Nielsen offers another bizarre benefit. you receive a consumer booklet full of hints on such topics as building a hutch and avoiding excessive use of bubble bath.

Yes, friends, you get all that just for taking the Nielsen oath, unless you're black. Then you get $2 a month and other benefits that were but alluded to by the Nielsen person. You see, blacks are more suspicious of the system and need a greater incentive to join the family, he explained, with the aside that blacks also seem to have more TVs, which they move around more than other ethnic groups.

Nielsen is not really interested in color unless you're talking about your set. Then they want to know the make and model number, which is recorded in the files at their headquarters in Dunedin, Fla.

Once they have this information and have you plugged into a computer line in New York, your whole life changes. You are afraid to turn on the TV. After all, one Nielsen family represents 500 other innocent viewers who may loathe "Welcome Back, Kotter," The responsibility is a great one.

My husband explained it this way: "I used to come home from work and turn on something I really wanted to watch. Now, I pore over the TV Guide looking for the best programming, things I should see or a new star who really needs a break. Ever since they put the box on there, I've been sneaking over to friends' houses to watch what I like on their sets,"

I soon followed his example, for fear Nielsen would bread up our marriage. Now the two of us go off into the night to see what we will on sets in bars, department-store showrooms and the homes of even the most casual acquaintances.

Before we go, we turn the dial to Channed 26 to soothe our consciences. It won't do Channel 26 a half-point's worth of good, since it, along with any other nonnetwork channel, is known to Nielsen simply as Other. As they see it, there are ABC, CBS, NBC and Other Alternatives.

So far, Other is ahead in this household. We just want to show the biggies thay can't have everybody. We would hate to see any program get a perfect rating, which is virtually impossible anyway since some Nielsen families don't even own TV sets. Nielsen wants to represent everybody, said the man who came to my door.

Sometines I wish I was like those brave souls who have resisted the tube. I've thought of getting rid of my Sony as a way out of all this new responsibility, but there's another option. That is to buy a second set, hide it in the basement under a pile of old sheets and view incognito.

The set must be hidden because the Nielsen man has vowed to return at some unknown time to question us about our latest buying urges. So far, I feel only the urge to channel hop ever 15 minutes to confuse Nielsen's computer. I do not lust after Stove Top Stuffing or Farah Fawcett hair yet. I am still safe. It would be safer, though, to pull the plug. You can do that, you know, but they don't like it.