How to inspect furnace filters?

[Don Y]

For "around the house", they are pretty much overkill. There are times when I'm trying to peer deep into the engine compartment (lots of obstructions, shadows, etc.) that benefit from their brighter, more focused light (than the little "penlight" or "cranklight" flashlights).

If I need to look "down the road" or into a neighbor's back yard, I'll drag out the Thor-X or something similarly sized.

But, to peer behind a computer (located UNDER my workbenches) or under a bed, etc., a little 2 AA cell maglite works just fine. Or, the three cell HD give(throw)aways.

Someone once claimed that AA and D cells were essentially the same "internals", just different shells. I'd find that hard to believe (unless it's akin to the "11 oz Coors" scam). One *hopes* the big, heavy, bulky D cells are actually *giving* you something for the extra size/weight!

Many of my devices have special "battery packs" (not counting the obvious candidates: laptops, cameras, etc.). One of my "digital magnifying glasses" uses the Sony "SmartLithium" modules that they used in their cameras. Many other things just require me to plug in a "charger" (wall wart) and the batteries charge inside the unit.

Exactly. I can buy 2032's in quantity as there are so many things that now use them; just keep them handy and "next time" I'm inside a computer, pull the old battery and replace it.

It's amusing how 9v "transistor" batteries have fallen from favor since the days of youth (in "transistor" radios). Aside from the smoke/CO detectors, I can' think of anything that uses them (so, why keep them on hand IN ANTICIPATION of a failure?)

[clare]

If you want to play with toys, not guess, and always know when the filter needs changing put a filter-check device on your furnace (like is used on large engine air-filtes). It is just a differential pressure guage - can be as simple as a manometer tube connected across the filter - from the air return duct to the return plenum of the furnace. A plugged filter will have a higher differential pressure than a clean one.

[clare]

I can still buy 2-packs of AA and AAA batteries - but they cost almost the same as a 4 or 6 pack when they go on sale. The 2 packs are never on sale. With batteries now having 10 year shelf life, buying 24 for $8 makes a lot more sense than buying 2 for $4.

[clare]

Blood glucose meters if you have a diabetic in the house, some good multimeters, my old garage door opener, the transmitter for my radio controlled "wire puller" (an old R/C truck that runs across suspended ceilings pulling network cables). I generally have a six-pack of them available - buy them when Canadian Tire has a good sale on, for less than a normal 4-pack - and often less than a 2-pack.

[Tony Hwang]

Ditto here but I try to use Lithium equivalent as much as I can. Last long time. Initial cost is high but at the end not really. I have drawful of batteries of all sorts.

[Vic Smith]

They measure capacity in MaH. This is useful:

With LED bulbs I'm satisfied with AA life-span.

I don't know why they still equip smoke detectors with 9v. But when I buy some more I'll look for AA equipped. I see they sell them.

[Don Y]

Most glucometers that I've seen are CR2032 or 2025. The trend seems to be to make the meters smaller and smaller. Also, they seem to be treated as largely disposable -- vendors wanting to "hook" you on a new meter to get you "addicted" to THEIR (highly profitable) test strips.

[One of the non-profits for which I've done volunteer work recycles medical... "discards" (not actually "waste", just things that are no longer "wanted" by hospitals, doctors, patients, etc. So, you see a LOT of glucometers!]

My portable DMM's (venerable Simpson and disposable "1 digit" HD units) have 9V batteries. The better (5 and 6 digit) DMM's are line powered.

Ours used a tiny -- 1/2 AAAA? -- 12V! battery. Replaced exactly *once* so the mate (two pack) is still in the refrigerator, somewhere

I had a box of lithium 9V batteries -- in hermetically sealed pouches (that smelled, internally, of alcohol or somesuch?) -- that I used to replenish my meters. The HD units I simply discard when the battery dies (or, when the displayed reading starts to look *too* incorrect to put much faith/effort into.

[Don Y]

Yes, but *actual* capacity is all over the map! Like buying a "bottle" of milk and discovering it really only holds a quart -- even though it *looked* like it was gallon sized!

I think it depends on the device, the peak power drain and the operating ("per use") lifetime.

E.g., our portable vacuum cleaner is good for a couple of minutes of operation (batteries are old and don't hold a strong charge). This is OK for us as we only use it when we have "a few crumbs" to clean up -- and don't want to deal with dragging out the REAL vacuum cleaner for such a small task.

A cordless soldering iron that I have is similar: uses lots of juice but for just a few seconds at a time. Then, set it back in its stand (which, amazingly!, is a CHARGER! :> ).

OTOH, if I'm stringing network cables on the underside of my work benches, I will typically use something like:

sitting flat on the floor, pointing upwards to illuminate the underside of the tables. After a while, the batteries (esp if they are the original HF batteries) go dark. So, swap them out (if rechargeable) with the spare set in the charger for *next* time.

[crap! I've been meaning Harbor Freight and think I've been saying "HD" -- instead of HF! :< Apologies to Home Despot!]

I think originally it was because the semiconductor "process" wasn't as effective at lower voltages and power levels. When making safety related things, change always draws attention to you:

Atty: And why, sir, did you authorize the change from the long standing, well proven, reliable design to this NEW design? The design that was present in the home of my client's LATE parents??

[Ralph Mowery]

That is what we used at work on the large building air filters. They had a motor on them so we could roll them up some when the pressure differential reached a certain level. They were on a large roll at the bottom and the takeup roll at the top.

There was a pickup tube on each side of the filter. Some were gauges with alarm switches,and some were simple fluid indicators.

[Tony Hwang]

Our detectors battery is only back up during power failure. Same with alarm clocks. Power failure is very rare in our neighborhood. Longest was like 5 hours once years ago during ice storm. This is there was one during severe thunderstorm, 20 mins. I have one watch runs on solar and equipped with 3 radios for time signal. Can receive and sync time in NA, EU and Asia.

[Ralph Mowery]

The blood meters are about like the printers. Almost give them away so you have to buy the strips made just for them. Just as many razors are. Give away the razor and charge a high price for the blades.

Sort of hard to carry around a line powered DMM. Outside of lab work there is seldom any need for more than the 4 1/2 digits of the Fluke meters that run on 9 volt batteries.

[Don Y]

Exactly. "Toilet paper dispensers" :>

I don't tend to do much design/debug work outside of my office so can rely on almost everything being line powered. E.g., I pulled an LCD TV into the living room last night to troubleshoot power supply (or main board) issues. Need 120V in order to test the TV so I've got that same 120V to power my DMM, DSO, etc.

I keep a HF DMM in the garage for the times when I suspect the battery in one of the vehicles may be low or faltering. But, then, I'm really only looking at how it *sags* when cranking and don't really care much about the

*actual* voltage that it is reporting. Probe battery terminals vs. battery cables to see if a high resistance connection, etc.

Or, operating as a glorified continuity tester...

[Tony Hwang]

Reminds me of old VTVMs. I still have one around. It can read HF RF rms with a probe.

[Stormin Mormon]

I'd offer to pay shipping, send em here.

But with the new Cree emitters, AA light is a bright as the old Mag. And the D cell three watt mags are excellent.

- . Christopher A. Young learn more about Jesus .

. .

[Ralph Mowery]

I worked in a large plant and mainly used meters in the field. If they had been line powered, I would have needed 50 to 100 feet of power cord.

I just got a HF DMM (free with purchase) a few weeks ago when the local store opened. Checked it to about 30 volts of DC and 130 volts of AC compaired with my Fluke meter. Most of the time the HF was within one number of the last digit. Ohms were slightly off, but probably within spec. As I did not need to, I did not try it, but there is one adjustment inside the meter to calibrate it.

It surprises me how accurate the inexpensive stuff is from China. I bought

4 3 digit DC volt meters (just a circuit board with displays and wire leads) for around $ 5 shipping included. Hooked all of them and a Fluke to a 0 -24 volt supply. All of them but one read the same thing. That was to a tenth of a volt. The other was sometimes off by one on the last digit. It had an adjustment, but did not try it as the meter was close enough for me.

[Stormin Mormon]

CY: Dollar tree has four packs of AA or AAA alkalines. Three packs of C or D carbon zinc cells.

CY: Those free HD short black lights are amazing.

CY: That used to be the case for some rechargble cells. Some C and D were 2500 mA hour, and were probably upsized AA. Alkalines and carbon zincs are ok with the bigger sizes.

CY: That's wisdom.

CY: 9V transistor cells are used in some emergency exit devices in stores. Also in the Comtek hearing amplifier box I use at church. Also my UEI non contact infrared thermometer. Also in Harbor Freight cheap VOM. Other than that, nothing (smile).

- . Christopher A. Young learn more about Jesus .

. .

[Don Y]

That's the new trend and, AFAICT, required in new construction. But, battery is still tested while running on AC power. For our (dual AC/DC) units: If any form of battery failure is detected the red LED light will flash and the unit will ?chirp? one time, followed by the warning message ?LOW BATTERY?. This cycle will occur once every minute, and will continue for at least seven days. Yeah, I *really* want to listen to that if it happens in the middle of the night! (not!)

Note that the detector can be temporarily silenced for *nuisance* alarms ("Dinner will be served at the sound of the smoke detector!") but not for the low battery reminder (I guess they don't consider it a NUISANCE to babble "LOW BATTERY" every minute for 10,080 consecutive minutes!)

Also, the detector *claims* it will conspire with its peers to adjust its sensitivity -- again, presumably, to minimize spurious alarms.

But, when the battery quits, it will nag you EVEN though you have AC mains powering the unit! (OhMiGosh! What if the power fails while the battery is low??)

We had a distribution transformer for the neighborhood catch fire which cost us most of a day. Another time, a cable fire in a vault (our utilities are below grade) ate up a day while new cables were "pulled".

I have a couple of crank-powered radios -- along withone that has a large *mainspring* that will drive the generator mechanism for a full 15 minutes! And, UPS's serve for short term backup power; plug a few CFLs into a UPS and the neighbors wonder why *you* (appear!) to have power but they *don't*! :> The batteries in the electric wheelbarrow will keep the house "lit up" for close to a day!

A friend is dropping off a genset for me to "rescue". This will allow us to keep the freezer in the garage operational during outages as well as the furnace (in the event it is a winter outage). Can't do much for the ACbrrrr during an outage...

[Tony Hwang]

When ICs are produced some flunks final QC test. They are not dead but does not meet standard. Cheap meters have those flunked chips. Radio shack sold many of those flunked stuffs for hobbyists. Problem with those are hit and miss and unreliable. If you use one of this bastard chips in a timing critical circuits. The result is very annoying.

[Don Y]

That;s why they make battery powered kit! :> My Simpson (VOM) came from a guy who used it for field work. It was too "pretty" to pass up, at the time. Now, it mainly collects dust as one of the smaller Fluke DMMs has about the same footprint (and I don't have to interpolate on an analog scale!)

We used to pick them up -- or whatever was the freebie du jour -- each week (no purchase required) on the way to volunteer gig. You'd find dozens of them lying around -- along with HF screwdriver "kits", scissors, box cutters, flashlights, etc. All "disposable" (not very good quality) but that's what you wanted -- you certainly didn't want to bring in *good* tools and discovered someone had walked off with them (or, simply LOST them!).

The plastic bits around the jacks for the test leads seemed to break quite frequently. But, again, no one was really treating these things like "investments".

It was there that I adopted the "disposable" mentality: picking up a meter, chasing down a pair of test leads and *then* discovering it's batteries were dead, or display cracked, or selector knob gummed up, etc. was frustrating enough -- the possibility that you MIGHT repeat this same exercise later that day, week, etc. made it much easier to just pitch the flakey items in the "recycle" bin. And, stop by HF next week for a replacement! :-/

Again, having many of them lying around, if you happened to probe the power supply on a disk drive and see "11.2V", you could pick up another meter and get a second opinion. If significantly different, take the one that is misreporting and discard it.

I had a guy I worked with at one of these places who would hold onto "partially working" things. Like, an AM/FM radio that only receives AM. "No, that's not an AM radio. That's trash! Look through that pile of AM/FM radios over there and see if you can find one that receives AM *and* FM!"

[DerbyDad03]