Archives for February 2013

A quick note about Heat pumps

2013/02/25 By staze

Last week, I had my yearly service performed on my heat pump system. They come out and clean the coils, and check everything to make sure it’s working. This year, though, the tech said there was something questionable, in that the subcool was too high, and that there seemed to be too big a temperature change on each side of the liquid line filter drier (LLFD). So, they suggested a service tech come out, and take a look. Fine, though I wasn’t looking forward to the cost.

Knowing resources are out there, I posted on the hvac-talk forums here, and got some opinions before the tech came out. Alas, the useful bit I didn’t get until after the tech came out. The key bit being: you can’t accurately measure subcool and superheat when the heat pump is in heating mode. So if your maintenance people tell you the subheat or subcool are off, and it’s 40°F out, and your house is being heated, you can PROBABLY ignore them. Obviously if they’re WAY off, it could mean something, but by and large, they’re only relavant in cooling mode. That is all. =)

Fluke 189 Data Logging Multimeter

2013/02/24 By staze

For years I have used a Radioshack 22-812 Multimeter. And while it worked just fine, I decided to treat myself to a “real” multimeter. Interestingly, I was at the beach at the time when I purchased the Radioshack multimeter before, and I was also at the beach when I bought this Fluke 189 over eBay for $200 (yes, they show up cheaper sometimes, but I’m still pretty happy with this price).

Unit arrived in good shape, packed very well, and overall very clean (couple spots were it was engraved by the previous owner, but nothing that some Dremel or labeling couldn’t cover), and the calibration sticker was still intact. Dropped some Eneloop rechargeables in it, and it powered right up.

First, some people hate the 189 series multimeters because they take AA batteries, and have terrible battery life relative to the classic 87 series that use 9V batteries and can run for weeks weeks on a single battery. Right now, I’m on my original batteries, with several hours of use, and had no problems at all. Plus, I can always carry extra eneloops. Rechargeable 9V’s, by and large, suck.

Anyway, the meter is a 50,000 count, 4.5 digit, True RMS meter with all the features you’d expect from the formerly top end Fluke handheld meter. Accuracy seems to be dead-on with everything else I’ve tested it against, and usability is top notch. The only complaint, really, is the power on/off being the selector switch. They resolved this with the newer version 2 of the meter where there is an actual power on/off button.

I have not, unfortunately, tested the logging or PC interface, since I don’t have the cable, but I hope to do this at some point. For it’s use as both an Electrical meter (mains), and Electronics meter (smaller projects), it has been perfect. The display is easy and fast to read, the battery life is just fine, and it really works just great. Fluke really are the de-facto handheld standard for good reason.

[xrr rating=5/5]

Radioshack 22-820 Pocket Multimeter

2013/02/24 By staze

As a quick review, I picked up a Radio Shack 22-820 based on a review of it (and other pocket meters) here, knowing it was no longer in production. I already have a couple of other meters (including a Fluke 189 that I bought days before this one). But I really wanted a meter for either my bag, or my car. So I found one at a Radio Shack and picked it up. All and all, it’s a great little meter. It’s small, rugged, and tests just about everything needed in a meter. Voltage, Resistance (with continuity), and amperage up to 200mA (which is a bit low if you wanted to use it for this, but heck, it’s only got so much space. Hard to have true current handling at this size… plus, try putting a 10A fuse in this space).

For $30, it’s a great little secondary meter, or a primary if all you ever do is check resistance/continuity and/or voltage. My only suggestion would be to pick up some basic aligator clip attachments (easier to test continuity on circuits that way).

[xrr rating=5/5]