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

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  

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  

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