RS 22-812 METER SERIAL DATA TRANSMISSION

[terri]

Happy New Year!<p>Maybe this isn't a good time to ask a question since with everybody offering good wishes back and forth, my question will drop to the bottom of the board.<p>But:<p>1. I have a Radio Shack 22-812 digital multimeter which has a serial port on it. I use it occasionally for various long-term data logging operations (temp, volts, etc). I like it a lot except that its software will only run in Windows. I find it quite awkward to keep a full-bore Windows machine running for the long periods of observation involved. Therefore, I would like to pick off the data and manipulate it immediately with a "lesser" machine (I can even do this on an old AT machine) and use DOS software to do calculations on the meter readings in more-or-less "real time."<p>2. Therefore, I tried picking off the data from the machine's COM port directly and discovered that the meter does not transmit numerical values to the meter software, but apparently transmits only which segments of the meter face display are on to the software. It looks like the meter software then interprets this to numerical values for recording in a log file. At least, so it appears.<p>3. I do not want to have to go to other methods of data logging, since (a) I do not log data that often, and, except for the fact that I cannot manuipulate the data immediately, using this meter's data logging is satisfactory; and (b) I am a world-class genetic cheapskate. (Yes, I've used the game port for raw data acquisition, but I don't like to.)<p>STUPID QUESTIONS:<p>(1) Am I right about how the meter sends information to the COM port? That is, only as segment-on information? If so, is this now a standard practice for connecting devices to COM ports? <p>(2) If so, has anyone developed an algorithm/software to interpret the segment information coming off the COM port from the RS 22-812 meter such that numerical operations can be performed directly and immediately? I can do this myself with much experimentation and lotsa logic, but what a pain in the padooky!<p>(3) Does anyone know if the previous version of this meter, the Radio Shack 22-805, which ran on DOS software, tranmits real numerical data, or does it transmit segment data as well?<p>(4) Does anyone have a 22-805 meter for sale?<p>[ January 01, 2005: Message edited by: terri ]</p>

[philba]

by segments, do you mean the segments of a seven segment display? If that's the case then it should be quite easy to take that data and turn it into a digit. You might have to play with figuring out how the segments are numbered.<p>Or you could have just googled for the protocol manual. http://www.rabbitsemiconductor.com/docu ... otocol.pdf<p>Associate each segment with a bit in a byte. Set the bit for each segment is on. Then use the byte (7 bits, actually) as an index to a look up table.<p>Decimal point needs to be handled specially and range information as well but it shouldn't take too long to figure it out.<p>[ December 31, 2004: Message edited by: philba ]</p>

[terri]

The data set seems to be for every segment on the meter face --which is duplicated on the computer monitor. That's why I said it would be a pain in the kerwunkies --sure, I could do as you sugggest, but being (a) lazy; and (b) time-constrained, I thought someone else might have done the legwork/logic on this. 10e6 TNX for the suggestion on the protocol site --somehow that missed my attention (gettin' old, doncha know). I'm sure your suggestion is a great one! Sounds like just what I needed!<p>Muchas Danke!
Sehr gracias!<p>[ January 01, 2005: Message edited by: terri ]</p>

[Mike6158]

Google is your friend <p>Zmeter

[Mike]

How long do you need it to run for????<p>my win 2000 web server runs well over a month between restarts, and even then I restart it without it needing to be so it doesn't ever crash.<p>Unless you need over a month, windows 2000 can run stable for that long, especially when not constantly using the processor.<p>Otherwise, you could get an old 486 computer and install NT 4 on it for your program to run. NT 4 is what 2000 is based on, and is close to as stable as it. Running on an old machine, it will run even longer than on a new computer.

[terri]

I'd run it for days, at the most, and I have a couple of old machines around. I've used the game port on an XT for this purpose many a moon ago. Right now, I'd like to use an old Compaq 286 SLT "laptop" since it's a small and neat-looking package and economical to run. <p>("Laptop!" Ha! It weighs 12 pounds! Ha!)<p>Yes, there are a lot of options as far as OSs and machines are concerned, but withal, DOS and the Compaq (which I can run on the batteries) seem to be the best all-around solution. If need be, I could even load an old copy of Win 3.1 on it, but there's still the problem of decoding the information in "real" time for manipulation. I still haven't had a chance to check out the site philba cited for insights into the protocol. I'm pretty sure that'll do the trick.<p>But right now I need coffee.<p>Lots of coffee.<p>Right now.<p>Hmmmm....coffee....<p>[ January 01, 2005: Message edited by: terri ]</p>

[terri]

Thanks, philba! That was pretty much what I needed to figure out what segments are on. Now I don't have to make a "decrypting" project out of it.

[bubba]

If you have a pocketPC there is a cheap data logging program for the 22-812 at
http://www.geocities.com/oxcarz12/DMM/index.html<p>
The pocketpc/multimeter data acquisition solution is handy cuz it's so portable.

[terri]

Well, it all works fine just as it is on my regular PC, but going back to my original question/problem, I did not want to tie up a full-bore modern machine (pocket or otherwise) for long periods of data logging and "real time" manipulation.<p>That's why I wanted to get the serial output as HTG numbers instead of segments which were "on" in the meter face. Of course, the software which came with the meter does this translation to HTG numbers internally, but I'm not about to dissect the software just to isolate the algorithms thay use to generate HTG numbers for real-time manipulation.<p>Philba's site cited above had the segment protocol information (which I had with the manual for the meter but cannot find) which I needed.<p>Nevertheless, I was impressed with the site you cited and just for the heck of it, I'm going to download the trial software and check it out as much as I can.<p>So thanks for the suggestion!

[dyarker]

How do you mean "tie up"? Unless you need the serial port to connect to the Internet; just start the logging program, minimize it, then run what other programs want. Or find a used computer with Windows 95, or newer, on it; and install the logging program on it.<p>Segments to numbers is a relatively simple lookup table routine. What kind of near real time manipulation do you mean?

[terri]

By "tie up," I mean just that. I do not like to have my regular machine running all the time (350 W), especially with data lines running all over the place and fans humming, etc. <p>I've got a dead silent 286 with an LCD screen I want to use for this. In addition, I can put this machine where I want it. <p>So that's the way I want to do it --with the LCD 286. In fact, I can load a copy of Windows 3.1 on the 286 and run the meter software on that, but I still would not be able to access the data log until I exited the program. I may want to get the logs of the data stream, or I may want to display a running average, or just display excursions, or BEEP when certain things happen ...or whatever. I used to log data with the game port on various machines, but that's sometimes awkward in terms of data conditioning, and that's why I bought the meter in the first place.<p>I have no problem with a table-look-up scheme and I am about to work up a program to do this. However, I did not know how the data stream for "segments on" was packeted, since I could not find the manual which came with the meter. I could have sat down and spent a couple of hours analyzing this. But the site kindly offered by a previous poster gave me this information, and as far as I am concerned, the problem is solved.<p>[ January 16, 2005: Message edited by: terri ]</p>