Checking out an old Radio Shack multimeter - with a special ability

first order of business as usual is checking out a different beer this is Bavarian dark lager from district brewing company in Regina Saskatchewan the tasting notes uh describe it as malt forward with notes of toffee raisin and chocolate yeah a fair bit of that toffee note in there that’s kind of neat it’s been a while since I’ve had a lager. So tonight I’m looking at this piece of vintage radio shack equipment now in the states radio shack ceased to exist a few years ago but in Canada that was what almost 20 years ago 2004 i think it was that radio shack stopped existing at least by that name they became a couple other things since then but uh yeah the radio shack name hasn’t existed in Canada for decades so what’s in the box it is this multimeter oh sorry there we go english side manual auto range dual display multi-reader a multimeter but the interesting thing about this one is it has a computer interface so this unit is from 1994. and as i said what makes it interesting and fairly unique in low cost multimeters is that it has a computer interface now of course ms-dos software isn’t going to be all that useful to me i think this is written for probably well windows 95 I’m guessing um is the windows software so yeah that’s not really going to work very well on my linux computer but i think i might have found some solutions for that on the good old internet anyway i found this thing um earlier this week when i was digging through a storage cabinet at work looking for something else and i remembered that we actually had two of these and the reason we bought them is because of that serial port which allows data logging so what’s in here we have a radio shack branded battery so that’s no doubt you know ish years old so i doubt it’s any good but that doesn’t matter because we had this thing powered from a 9-volt battery eliminator which is just that a 9 volt battery snap that’s kind of neat there’s a little condom for the battery so that if it leaks it doesn’t uh cause all kinds of problems that’s kind of nice looks like we had to customize that to make it work not a big deal that’s interesting us and german patent manufacturing korea and then all the different radio shack variants the model number 22-168a if you look that up online you can find the manual and a bunch of projects and stuff for it one of which i’m going to try later so cables that are with this as a set of leads fairly standard leads they’re not silicone wire or anything but they’re nice and lengthy and then there is the serial cable all mixed in here so standard db9 on that end and these funky little bent pins on this end which if i remember correctly yeah plugs into there and that allows you to pull data out of the meter live and just save it onto your computer for later analysis and that’s the reason that we bought these things at work in the first place if i remember correctly they were about 100 bucks or something each so expensive by radio shack standards but as a multimeter with data logging functions that’s pretty cheap especially back then yep it works and there’s no reason why it shouldn’t it didn’t have batteries dying in it it was just sitting there working first thing let’s test its old battery I’m gonna guess it’s yeah seven volts that’s better than i expected actually so i think what I’ll do is just quickly compare this thing for accuracy against the most accurate meter that i’ve got available to me which is this fluke 298 I’ll just do a few quick tests that won’t be too extensive so here is dc volts mode I’ve got five volts on my little power supply over there they’re both tied in parallel here i’d call that pretty much the same so there’s 19 volts coming out of here 1903 18.986 definitely close enough for most non-lab grade jobs that’s just fine actually this is an auto ranging they’re not auto ranging so there you go yeah that’s 200 volt range this one is auto ranging so yeah that’s reasonable enough no complaints there okay let’s try impedance i’ve got our resistance i guess i’ve got this stack of resistors in parallel here which if i remember correctly is close to 75 ohms yes 72.85 on the fluke 72.9 on the radio shack that’s pretty reasonable uh what are the leads measuring at less than half an ohm there on the fluke i’m going to guess it’s about the same if not a bit lower yeah 0.15.

16 so not enough to throw a measurement like that off let’s try 06:04 - a high resistance how about 25k yeah i know it doesn’t have to be a power resistor but i just happen to have that one right handy dandy so there is that one 24.31 that’s pretty bang on for what it says okay cool do we have anything else how about something right in the middle there’s 2.5 k 2.46 2.46 bang on that is so much better than my original radioshock multimeter that i bought as a teenager this thing is the least accurate multimeter that i have even worse than these guys which are actually pretty damn close to this fluke one more thing i can fairly easily try um ac line voltage 123 and a third 123.5.6 that’s no problem with that at all so that’s cool to know that it’s uh nice and accurate i’m curious to see what’s inside this guy uh looks like it shouldn’t be too hard to open up just four screws I’ll quickly do that and bring you back just before i open it because screwdrivering isn’t all that exciting to watch i don’t think there we go so little piezo buzzers in the back there oh a bunch of shielding that’s like anti-static bag kind of plastic for shielding that’s nice screw it down through there ceramic fuse there we go deeper in looks like there’s a nice big chip right there doing most of the heavy lifting I’m guessing so yeah i guess uh yeah let me pull off all those screws and come back in a second here and the last screw okay and how can i lift that out of there trying not to destroy anything because i do want this thing to go back together there we go okay what’s that okay that’s the insulating sleeves for the probes there’s some tweezers here can’t get my big mitts in there right so there is another little bit of insulation there’s the capacitance connectors there’s some connectors that go down to the main board several of them so one connector down there one there a double row there there’s the capacitor check there is the what is that the transistor check power button is an actual button and the other three buttons the mode and ac dc and set reset oh it’s actually labeled there function set reset and ecdc those are just little resistive button things and then two calibration nice so this big maxim chip a max 130 cpl and this they’re upside down but whatever uh what is this met x metex uh ks 57c 2016-13 which is probably the metering chip there’s a crystal there for it this is way different than a mo than the modern meters with their single blob chip on board thing isn’t that so yeah obviously i’m not going to touch this calibration part or this little variable capacitor down here oh variable resistor sorry vr2 i’m not going to go too deep into it i’m obviously not going to reverse engineer it that would just be insanity but oh and then there is a zebra stripe or there and up there actually uh it goes down to the zebra stripe connectors for the for the lcd oh hey on the back of the lcd you see that mitex or medex same brand as this chip here with a date code of 1998 fifth month uh may 31st of 1998 so there that dates it pretty definitively okay there it’s back together let’s just make sure it still works power on volts dc should be about 19 or so there you go 19 exactly good so it still works always the first thing to check once you’ve taken it apart and put it back together right sure now then about this serial port clearly i’m not going to be able to show you the the original dos and windows software that came with it partly because i don’t have a dossier windows machine here partly because they don’t have a machine that will read this disc anymore let’s see if i can find some kind of a usb to three and a half inch floppy drive at some point i’m if i had wine running i might be able to run that software but i don’t so plan b i have a usb to serial adapter which should theoretically allow this to be read by the computer because in the manual it gives some technical information this is from the golden age of radio shack when they actually gave you technical information on the things that you bought so this thing talks at 1200 baud uh it’s seven bit no parity two stop bits and there is the frame of data that comes out of it so that’s fairly easy and it even tells you how to write a super basic basic program to uh to deal with this which is really cool however i haven’t bothered to install basic on my computer but all you have to do is give it a d and it will give you a single reading so you can just write something to send it to d every x number of seconds and it will dump some stuff out to you so let’s uh just try and do that manually okay so i am set up here on uh my usb serial depth here 1272 and if i send it a capital d bugger all happens that’s what it said right 1200 seven bit no parity two stops right okay send to d send a capital d nothing okay maybe that’s not the thing for it fine now something else i found in my searching was this at linuxtoys.org i’ll put a link down below um so somebody went through and figured this thing out back in the day when it was a current item and they wrote this little c program for it which is pretty cool so i have actually gone and compiled this up i did have to add this standard library to it to make it compile but it seems to have compiled so if i run it i’ll see if i can talk to make that work oh hey a result so this happens every 60 minutes so i’m just going to uh well i’ll speed the video up and i’m going to change the voltage that it’s reading on my power supply each uh a bit each time let’s pull it down half a volt or volt or something and i’ll come back in a little bit here so while that’s happening let’s just go and find out this uh matex or met x or however you pronounce it seems like they’ve been in uh in a bunch of different industries for over 50 years among the things that they make currently are these digital meters all industrial stuff all fairly heavy duty so i guess that somewhat explains how something so uh interesting and heavy duty and accurate ended up in radio shack’s uh catalog it was made for them by somebody who actually knows what they’re doing which is pretty pretty standard actually reader shack had a lot of deals like that with sony and sure microphones and crown microphones and cos headphones i guess that shouldn’t surprise me really back to this there’s a handful of readings that this thing’s taken over a minute or so i’m just going to uh i’m just going to put it onto this resistor here which is around 75 ohms spin that around ohms and we’ll see what the next reading says when it comes out oh there we go 77.

6 ohms that’s uh so you can track pretty much anything 16:49 - of course you could you could rewrite that program there it is here you could rewrite that program to dump the data to a file or something you can change the time on it or whatever you need to do it is c so anybody who’s been messing with arduinos for a while should be able to translate this at least a little bit and figure out what it’s what it’s doing you could tinker and just recompile it and the beauty of having a linux system is the com the gcc compiler is pre-installed it’s just one command to recompile this so that’s pretty slick that satisfied my curiosity um and i can actually still use this guy with in the modern day even though it’s got a fairly old-school connection on it with just a simple little ebay usb to serial adapter and a chunk of random code that i found online it still works just as well as it ever did i hope that was a bit of a nostalgia trip for some of you and a bit of a curiosity for people who hadn’t encountered this guy before i had fun uh digging through it and just reminding myself of what this guy could do thanks for watching i do appreciate that as always comments and questions down below there’ll be some links down in the description i’m pretty sure i’ve mentioned that already i will talk to you later.