A look at the RS 22-812 meter - Page 1
Forum section: electronics / general

author: IanB
author_rank: Super Contributor
timestamp: October 30, 2011, 07:04:12 am
content: I thought I'd post a few pictures of this meter as it has some thoughtful design details that other products could learn from. I have posted before that I really like this meter and own two of them.It has a range of useful features like min/max, rel, hold, frequency and uA. There is a removable soft rubber bumper on the outside for drop protection. But the main reason I like the meter is for the data logging PC interface.When I first got the meter the factory calibration was not that good, but if you open it up there are clearly labelled adjustment pots and you can tune it up. I adjusted DC volts and it now reads quite accurately.The battery compartment has a machine screw and a brass insert. A nice feature here is the screw is captive so you can't lose it.It uses a 9 V battery that some people dislike, but in normal use it consumes only 960 uA. The battery lasts forever.The case opens with three more machine screws into brass inserts. These screws are also captive and can't go astray.The fuses have handy little ribbons to help remove them, and there are spare fuses stored inside the case so you won't be stranded if a fuse blows unexpectedly.The data logging interface is isolated behind a plastic cover in the back half of the case. The data logging feature is one of the main reasons for owning this meter. The protocol is documented making it easy to hook the meter up to your own programs.The continuity buzzer is also in the back half of the case and connects with two springs so there is no captive wire leading to it.

author: elliott
author_rank: Regular Contributor
timestamp: October 30, 2011, 08:20:37 am
content: Looks like the only thing that has changed in the 10 years since I bought mine is the color of the rubber holster.

author: ciccio
author_rank: Frequent Contributor
timestamp: October 30, 2011, 08:41:06 am
content: Nice instrument, for 49 USD it is a good deal.I see the PCB is labeled CCTECH . Is this the original manufacturer?

author: PeterPatnter
author_rank: Newbie
timestamp: December 15, 2011, 04:43:30 pm
content: Dear Ian,Thanks for a GOOD review -- I have had one of these meters for eight or so years, and agree about all the details you mention, but have been having a major problem with mine:It blows fuses -- immediately, I think -- and otherwise doesn't work. The one that goes out is the 500 mA.I suppose I could take it somewhere for service, but do you have any ideas for a quick cure?Thanks!- Peter

author: IanB
author_rank: Super Contributor
timestamp: December 15, 2011, 05:02:16 pm
content: Do you have a second meter to test with? That way you can make some measurements on the faulty meter.Have you gone through the ranges after replacing the fuse to find out which ones work and do not work? For instance, does the resistance range work as expected, or the 10 A current range?If the fuse blows when you try to measure DC volts on the DC volt range, it suggests a problem with the rotary selector switch. Using the resistance range of another meter, you could measure the internal resistance of the faulty meter while the faulty meter is set to volts. The resistance should measure about 10 megohms. If it is very low instead there is a definite problem.Assume you can locate the problem as above, you would carefully disassemble the meter and look for mechanical damage or misalignment, or electrical short circuits. In particular you would have to disassemble the range selector switch and see if it is all intact with the metal wipers working properly and making good contact with the circuit board.It's doubtful that paying someone to service an eight years old "low cost" meter will be cost effective. It would work out cheaper just to buy a replacement.

author: PeterPatnter
author_rank: Newbie
timestamp: December 15, 2011, 06:01:04 pm
content: Ian, thanks for the good suggestions.

author: grenert
author_rank: Frequent Contributor
timestamp: December 23, 2011, 02:36:23 am
content: This meter is currently on sale for $39 until Dec. 24.http://www.radioshack.com/product/index.jsp?productId=2103962

author: FenderBender
author_rank: Super Contributor
timestamp: January 02, 2012, 06:44:09 pm
content: Wanna do a teardown of that Protek meter? I've seen several clones of it...and I'm curious.